Caltech's Seismological Laboratory (Seismo Lab) is a place of legends. Founded more than a century ago, it is the birthplace of the Richter scale and the Southern California Seismic Network, and its media center is the go-to source of information for people around the globe when the ground shakes. Today, the Seismo Lab continues to lead the way in earthquake research and the study of planetary structures and dynamics. With the creation of the Clarence R. Allen Leadership Chair, the lab will have resources to ensure its impact on public safety and our understanding of how the earth works stretches well into the future.
To celebrate its 100th anniversary, the Seismo Lab hosted a scientific conference in fall 2022. Terence Barr (BS '84), chair of the GPS Chair's Council, viewed the event as an opportune time to encourage members to support a leadership chair named in Allen's honor."It was especially appropriate to honor Clarence Allen, who had contributed so much to the Seismo Lab and GPS," notes Barr, who was inspired to pursue a degree in geophysics after taking a class with Allen.
Dayna Salter (BS '76), who joined the Chair's Council in 2021, concurs. She studied seismology and geophysics, with Allen as her adviser. "He put me at ease when it felt daunting to talk to professors one-on-one," remembers Salter, who was a member of the third freshman class of women admitted to Caltech. "I have nothing but positive memories of him, which makes it all the more important to donate funds for this chair."
In January 2023, Michael Gurnis, the John E. and Hazel S. Smits Professor of Geophysics, was named the inaugural holder of the Allen Leadership Chair. Gurnis, who has directed the Seismo Lab since 2009, develops and uses computational models to better understand plate tectonics and mantle dynamics. He also directs the Schmidt Academy for Software Engineering, which trains software engineers to set new standards in scientific software.
Gurnis says one of the hallmarks of the Seismo Lab is that it provides opportunities for graduate students to hone diverse skill sets by working with multiple faculty advisers. "Many young scientists will benefit from Clarence's generosity," he adds, "by having opportunities to initiate highly innovative research collaborations with faculty."
In addition to supporting faculty and students, Salter says the leadership chair will give the Seismo Lab increased resources for connecting with the public, helping more people better understand and prepare for earthquakes on a local level and beyond.
"Clarence was a real integrator across the division, and now Mike Gurnis is that bridge for bringing faculty, students, and the greater community together in the search for new knowledge," Grotzinger says.
Read the full story here.
Zhan, a Caltech professor of geophysics, specializes in turning underground telecommunications networks into earthquake detectors. In Pasadena, for example, he figured out how unused strands of optical fiber in the city’s telecommunication cables could detect seismic waves and do the work of 5,000 sensors. In January 2023, he traveled to the end of the earth for a National Science Foundation–funded project to prove a similar approach could work in Antarctica. The goal: to listen for seismic waves in the ice that could signify “icequakes” and other seismic activity, which could help scientists understand the physics and deep structure of glaciers and ice sheets, and how the polar regions are changing under ongoing climate change. Zhan also hopes to use these waves to study the hidden base layers of the ice.
He knew that the United States’ Amundsen-Scott Station, located at the South Pole, had spare fibers in the telecommunications lines that formerly connected it to a nearby geophysical research station. In the 20 years since that station had been relocated, the cable had become buried in 10 meters of new ice. Still, Zhan thought that if the cable remained in good enough condition, it could still be possible to use it to detect seismic waves traveling through the ice, just as he typically does in California and with cables running under the sea to detect earthquakes.
“By converting cable into a sensor, you have a very dense array of sensors that you couldn't deploy otherwise,” Zhan says. “I felt like this must be a very good idea for studying glaciers.”
To find out if that was indeed the case, he and his fellow researchers would need to create their own vibrations on the surface of the ice and see how well the repurposed telecom lines could pick up the resulting seismic waves. Hence the thumping. On their long journey, first to the McMurdo Station on Antarctica’s coast and finally to the South Pole deep in the heart of the frozen continent, Zhan and colleagues lugged an old-fashioned 8 kilogram sledgehammer as well as a 40 kg piston-powered mechanical hammer mounted to the back of a snowplow that could pound the frozen surface. Once he saw that Amundsen-Scott’s old telecom lines had enough remaining strands of fiber intact for his experiment, he couldn’t wait to get started-- even though the plow-mounted hammer wasn’t ready yet.
“I grabbed my sledgehammer and ran outside,” Zhan says. “I had to do some tests, and I hammered there about 40 times.” The findings shook him: Because the South Pole is such a quiet place, the detection instrument Zhan had linked to the old buried telecom lines could detect seismic waves from a sledgehammer strike from more than a kilometer away, 10 to 20 times farther than would be possible in noisy California.
“Even with all those preparations, when you first go there, it still is amazing how cold it is,” he says. “Especially your face. Whenever it’s exposed, it just feels so cold, and the air coming out immediately freezes on [your glasses]. There’s no way for you to wipe it off.”
Back in the Northern Hemisphere, Zhan is still receiving readings from the detector his team left behind. It will continue to gather data throughout the Antarctic winter, which is too inhospitable for human scientists to hang around. For Zhan, fieldwork at the South Pole certainly gave him a new understanding of the meaning of cold.
Read the full story here.
As you are reading this, more than 400 miles below you is a massive world of extreme temperatures and pressures that has been churning and evolving for longer than humans have been on the planet. Now, a detailed new model from Caltech researchers illustrates the surprising behavior of minerals deep in the planet's interior over millions of years and shows that the processes are actually happening in a manner completely opposite to what had been previously theorized.
The research was conducted by an international team of scientists, including Jennifer M. Jackson, William E. Leonhard Professor of Mineral Physics. A paper describing the study appears in the journal Nature on January 11.
"Despite the enormous size of the planet, the deeper parts are often overlooked because they're literally out of reach—we can't sample them," Jackson says. "Additionally, these processes are so slow they seem imperceptible to us. But the flow in the lower mantle communicates with everything it touches; it's a deep engine that affects plate tectonics and may control volcanic activity."
Many questions remain unanswered about the mechanisms that allow this convection to happen. The extreme temperatures and pressures at the lower mantle—up to 135 gigapascals and thousands of degrees Fahrenheit—make it difficult to simulate in the laboratory. For reference, the pressure at the lower mantle is almost a thousand times the pressure at the deepest point of the ocean. Thus, while many lab experiments on mineral physics have provided hypotheses about the behavior of lower mantle rocks, the processes occurring at geologic timescales to drive the sluggish flow of lower-mantle convection have been uncertain.
The lower mantle is mostly made up of a magnesium silicate called bridgmanite yet also includes a small but significant amount of a magnesium oxide called periclase mixed in among the bridgmanite in addition to small amounts of other minerals. Laboratory experiments had previously shown that periclase is weaker than bridgmanite and deforms more easily, but these experiments did not take into account how minerals behave on a timescale of millions of years. When incorporating these timescales into a complex computational model, Jackson and colleagues found that grains of periclase are actually stronger than the bridgmanite surrounding them.
"We can use the analogy of boudinage in the rock record, where boudins, which is French for sausage, develop in a rigid, ‘stronger,' rock layer among less competent, ‘weaker,' rock," Jackson says.
"As another analogy, think about chunky peanut butter," Jackson explains. "We had thought for decades that periclase was the ‘oil' in peanut butter, and acted as the lubricant between the harder grains of bridgmanite. Based on this new study, it turns out that periclase grains act as the ‘nuts' in chunky peanut butter. Periclase grains just go with the flow but don't affect the viscous behavior, except in circumstances when the grains are strongly concentrated. We show that under pressure, mobility is much slower in periclase compared to bridgmanite. There is an inversion of behavior: periclase hardly deforms, while the major phase, bridgmanite, controls deformation in Earth's deep mantle."
Understanding these extreme processes happening far below our feet is important for creating accurate four-dimensional simulations of our planet, and it helps us comprehend more about other planets as well.
The paper is titled "Periclase deforms more slowly than bridgmanite under mantle conditions."The study's first author is Patrick Cordier of the Université de Lille and Institut Universitaire de France. Additional co-authors are Karine Gouriet, Timmo Weidner, and Philippe Carrez of the Université de Lille; James Van Orman of Case Western Reserve University; and Olivier Castelnau of the Arts et Metiers Institute of Technology in Paris. Funding was provided by the European Research Council and the National Science Foundation.
Read the full story here.
Olivia Pardo wins best poster presentation at IUCr workshop December 10, 2022. Only one poster award is given at the workshop. Making this a very prestigious award!
Congratulations Olivia !
The Organizing Committee of the 2022 IUCr HP workshop offered a limited number of awards to cover the accomodation costs. The awards are intended for scientists who have graduate student, postdoctoral, or early career (untenured) faculty appointments.
Congratulations Olivia and Ben!
Pasadena and Alhambra high school sophomores and juniors are delving into earthquake science as part of the Seismological Laboratory's new Caltech Earthquake Fellows program.
Over their four months in the program, participants experience a compressed version of the research process, posing questions, gathering data with individual seismometers, and collaborating in small groups to analyze and interpret findings. The inaugural group of 11 students will present their research in a lecture hall to their mentors, friends, and families on September 17.
Offered in partnership with the Dr. Lucy Jones Center for Science and Society, the Caltech Earthquake Fellows program works to strengthen ties between Caltech and surrounding communities and to encourage students, particularly those from underrepresented backgrounds, to pursue scientific careers.
The fellowships offer a one-month immersion in seismology on Caltech's campus in the summer, flanked by Saturday sessions in spring and fall.
During their month at Caltech, students toured the Seismological Laboratory and the wider campus; attended talks by experts in geophysics, seismology, and disaster preparedness; learned about college and scientific careers; conducted research; and built coding and data visualization skills useful in several fields of study. After finishing the program, participants will keep their laptops and seismometers and receive a $1,000 stipend.
Graduate student Jimmy Atterholt says he learned vital lessons by contributing to the program's seismology curriculum and mentoring students as they conducted original research, several of whom did so for the first time. He values practice in describing concepts at the high-school level, explaining that while seismology is an upper-level college course, people who become seismologists are often called on to talk publicly about earthquakes.
Click
here to read full article.
Geoscience students at Caltech will now have access to industry standard seismic data processing software, thanks to a $322, 230 donation from IHS Markit (NYSE: INFO) a world leader in critical information, analytics and expertise to forge solutions for the major industries and markets that drive economies worldwide.
Caltech Seismological Laboratory professor Joann Stock has been awarded three Educational Network Licenses for each of the following IHS Markit software products: Kingdom Geoscience Bundle, LoadPAK, VelPAK and Petrophysics.
The products will be used by Professor Stock and PhD graduate students doing research using multichannel seismic data (SEG-Y files). They will be used for analysis and interpretation of MCS data collected in the Guaymas Basin, Gulf of California. For this project, PhD student Adriana Pina is building a seismic stratigraphic model of the basin. We will use downhole geophysical logs, shipboard petrophysical measurements on the core samples, and core-log-seismic integration to ground-truth the characterization of the seismic stratigraphy that was interpreted from the MCS data prior to drilling the holes. We will expand the study area outside of the region that was drilled on IODP Expedition 385, in 2019. The products will be used in southern California: principally in Prof. Stock's lab in North Mudd at Caltech.
For more on Kingdom Software Educational Licenses click here
Geophysics graduate student Oliver Stephenson, who will graduate next month, will head to Washington, DC, in September on a William L. Fisher Congressional Geoscience Fellowship to help policymakers base decisions on solid science.
The fellowship lasts one year and Stephenson intends to use this opportunity to help launch a career in science policy, working with government officials to ensure that science informs decision-making. He plans to use the scientific training he received at Caltech to try and make the world a better place in the most direct fashion he can.
A geophysicist by training, Stephenson's main areas of interest in science policy are climate change mitigation, natural hazard preparedness and response, and the ways in which artificial intelligence (AI) will shape society.
Once in Washington, Stephenson will interview with U.S. senators, representatives, and others. After receiving offers for placements, he'll select one and get to work, either in a lawmaker's office or on a committee tasked with working on a specific problem. Stephenson says he hopes to spend the next year learning how Congress works, and how he can have a positive impact on the world by working with congressional leaders.
Funding for the fellowship is provided through an endowment established by the AGI Foundation to honor William L. Fisher, professor and Leonidas T. Barrow Centennial Chair Emeritus in Mineral Resources at the Jackson School of Geosciences at the University of Texas at Austin. More information can be found on the American Geosciences Institute website.
Click here to read full article written by Robert Perkins.
Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates pictured (from left to right) Celeste Labedz, Stacy Larochelle, Vasilije Dobrosavljevic, Zhe Jia, Minyan Zhong with Professor Zhongwen Zhan.
We would like to recognize the students who received a Master of Science. (pictured from left to right) Sihe Chen (Planetary Science), and Jiaqi Fang (Geophysics), not pictured Alex Berne, Jack Wilding and Cijin Zhou.
Valeria Villa received the Outstanding Student Presentation Award from the 2021 AGU Fall Meeting held in New Orleans, LA, December 13-17, 2021. The title of the study is “3D Basin Depth Map for the San Gabriel, Chino, and San Bernardino Basins".
The Outstanding Student Presentation Awards (OSPAs) promote, recognize and reward undergraduate, Master's and PhD students for quality research in the Earth and space sciences. It is a great honor for young scientists at the beginning of their careers. The process relies entirely on volunteer judges. Typically the top 3-5% of presenters in each Section are awarded an OSPA and all judged students are provided feedback.
Congratulations Valeria!
Click here for information on the AGU Student Presentation Award.
Scientists have uncovered the source of a mysterious 2021 tsunami that sent waves around the globe.
In August 2021, a magnitude 7.5 earthquake hit near the South Sandwich Islands, creating a tsunami that rippled around the globe. The epicenter was 47 kilometers below the Earth’s surface — too deep to initiate a tsunami — and the rupture was nearly 400 kilometers long, which should have generated a much larger earthquake.
A new study revealed the quake wasn’t a single event, but five, a series of sub-quakes spread out over several minutes. The third sub-quake was a shallower, slower magnitude 8.2 quake that hit just 15 kilometers below the surface. That unusual, “hidden” earthquake was likely the trigger of the worldwide tsunami.
The study was published in the AGU journal Geophysical Research Letters, which publishes short-format, high-impact papers with implications that span the Earth and space sciences.
“I think a lot of people are daunted by trying to work on events like this,” said Hubbard. “That somebody was willing to really dig into the data to figure it out is really useful.”
Both Jia and Hubbard noted a long-term goal is to automate the detection of such complex earthquakes, as we can for simple earthquakes.
To read the full AGU press release click here.
A $75 million gift from the late William (Bill) H. Hurt has established a suite of endowed early-career professorships at Caltech that brings young faculty together to collaborate, build connections across disciplines, and engage in research and teaching that has the potential to define new fields of study, develop technologies, and advance innovative solutions to address the greatest challenges of the day.
The program reflects Caltech's and Hurt's shared belief that extraordinary young scientists and engineers can make profound contributions if they are empowered to connect with colleagues outside of their field around humanity's most pressing problems. The program will make possible meaningful and intentional interactions by providing secure funding resources and the intellectual freedom such resources allow, leaving the scholars free to derive unexpected insights, forge new lines of research, and communicate their progress with peers and students. The William H. Hurt Scholars program will further Caltech's impact across science and engineering, ensuring that the Institute can continue to not only attract extraordinary thinkers and researchers from around the world but to provide each of those scholars with the creative, collaborative, and multidisciplinary environment that is most conducive to discovery.
Upon their arrival at Caltech or appointment to the program, William H. Hurt Scholars will receive unrestricted funding and gain a network of colleagues with whom they will interact through programming designed to catalyze new research ideas and collaborations.
The four faculty members who make up the inaugural cohort of William H. Hurt Scholars are:
Each year thereafter, up to three additional professors from any of Caltech's six academic divisions will be selected. When fully developed, the program will support 18 early-career scientists and engineers, who will rotate off after six years in the cohort.
"Bill wanted his gift to help create a new class of scholars who were educated beyond their fields and could address the major issues of tomorrow," says Bernadette Glenn, Hurt's stepdaughter-in-law and the president of the WHH Foundation. "There is a wonderful sense that this program will work very well and help Caltech continue to have a massive impact on society."
Read the full story here.
The technique is being developed to detect venusquakes. A new study details how, in 2019, it made the first balloon-borne detection of a quake much closer to home.
Between July 4 and July 6, 2019, a sequence of powerful earthquakes rumbled near Ridgecrest, California, triggering more than 10,000 aftershocks over a six-week period. Seeing an opportunity, researchers from NASA's Jet Propulsion Laboratory and Caltech flew instruments attached to high-altitude balloons over the region in hopes of making the first balloon-borne detection of a naturally occurring earthquake. Their goal: to test the technology for future applications at Venus, where balloons equipped with science instruments could float above the planet's exceedingly inhospitable surface.
And they succeeded. On July 22, highly sensitive barometers (instruments that measure changes in air pressure) on one of the balloons detected the low-frequency sound waves caused by an aftershock on the ground.
In their new study, published on June 20 in Geophysical Research Letters, the team behind the balloons describes how a similar technique could help reveal the innermost mysteries of Venus, where surface temperatures are hot enough to melt lead and atmospheric pressures are high enough to crush a submarine.
"Much of our understanding about Earth's interior – how it cools and its relationship to the surface, where life resides – comes from the analysis of seismic waves that traverse regions as deep as Earth's inner core," says Jennifer M. Jackson, the William E. Leonhard Professor of Mineral Physics at Caltech's Seismological Laboratory and a study co-author. "Tens of thousands of ground-based seismometers populate spatially-dense or permanent networks, enabling this possibility on Earth. We don't have this luxury on other planetary bodies, particularly on Venus. Analysis of surface features on Venus suggest recent volcanic activity and some regions appear reminiscent of subduction zones. Observations of seismic activity there would strengthen our understanding of rocky planets, but Venus' extreme environment requires us to investigate novel detection techniques."
Read the full story at JPL News.
Clarence Allen (MS '51, PhD '54), professor of geology and geophysics, emeritus, and a prominent seismologist, passed away on January 21, 2021. He was 96 years old.
Allen was born on February 15, 1925, in Palo Alto, California. His father, an educator, began his career teaching blacksmithing and eventually became a professor at the Claremont Colleges; while his mother died during the birth of his sister when he was in sixth grade. He developed an early love of geography, cartography, and the outdoors while on family road trips throughout the American West, interests that left him well suited for his role as a navigator in B-29s when he served in the Army Air Corps in the Pacific during World War II. He began his higher education at Reed College in 1942, but left to spend three years in the service from 1943 to 1946, and then returned to graduate with a bachelor's degree in physics in 1949.
While at Reed, Allen realized that he was not a mathematician or theoretical physicist at heart, as he favored the concrete over the abstract. He connected with a geology professor at the University of Wisconsin who introduced him to the field of geophysics, the study of the physics of the earth.
"I'm not even sure I realized that seismology, for example, was a branch of geophysics," Allen said in a 1994 interview. "But to me, it looked like a way that I could get out of pure physics, which I thought I wasn't going to really succeed in anyway, and into something where I would have the chance to be outdoors a little more."
He turned down several graduate schools, including an offer of a fellowship to go to UCLA, to pursue a master's at Caltech. At the time, almost all of the students there were WWII veterans. "Given my natural interest in maps, I just fell in love with doing geological work in the field," Allen said. He earned his master's and doctoral degrees from Caltech in 1951 and 1954, respectively. His thesis explored the San Andreas Fault in the San Gorgonio Pass area (between Beaumont and Palm Springs), which launched his interest in studying fault structures.
Once he earned his PhD, Allen spent a year as an assistant professor at the University of Minnesota, but was recruited to come back to Caltech after the passing of John Peter Buwalda left a need for a structural geologist in the Division of Geology (which would eventually become the Division of Geological and Planetary Sciences). Given Caltech's strength in geology, Allen said that, "When I got the call to come back, I didn't really think twice about it...." Allen joined Caltech's faculty in 1955 as an assistant professor. He became an associate professor in 1959 and full professor in 1964.
Allen joined Caltech at a time when the Institute was expanding the seismic network in California. He was an early pioneer of the field of seismotectonics, studying the relationship between the faults in a region and the earthquakes that occur there. He worked with many of the early legends of seismology at Caltech, such as Charles Richter (PhD '28) and Beno Gutenberg, but joined the Caltech Seismological Laboratory at a time when the torch was being passed from them to the next generation of seismologists. Frank Press took over as director of the Seismo Lab in 1957, bringing in new computer technology and broadening the lab's scope of field exploration, expanding the lab and recruiting younger staff.
At the Seismo Lab, Allen bridged the gap between geophysics and geology, says Lucy Jones, visiting associate in geophysics. "One of the real problems with earthquake science is that it requires lots of expertise. You have physicists doing theoretical wave equations, interpreting waves as they travel through the earth; while geologists go out and map what they see, using geometric relationships between various bodies to understand it. Clarence was somebody who could go between the two groups."
"Clarence was a superb field geologist, but with his undergraduate physics training he could communicate very well with many Caltech seismologists whose primary background was physics," adds Hiroo Kanamori, John E. and Hazel S. Smits Professor of Geophysics, Emeritus.
Allen served as the interim director of Caltech's Seismological Laboratory from 1965–67 and was acting chairman of the Division of Geological and Planetary Sciences from 1967–68. During his career, he was most known for his contributions to the evaluation of seismicity and fault movements in regions where earthquakes are common.
On February 9, 1971, a magnitude-6.6 earthquake ripped through the northeastern corner of the San Fernando Valley, killing 65 people and causing more than $500 million in damage. The event not only prompted an expansion of earthquake monitoring in Southern California, but spurred Allen to become involved in earthquake legislation. In the aftermath, Allen went to Sacramento and explained to legislators that geologists know where the active faults are and that an earthquake like San Fernando would certainly happen again in California. In 1972, the California legislature passed the Alquist-Priolo Earthquake Fault Zoning Act, which prohibits building across active faults.
"It was really because of Clarence spending the time and the effort to help people understand that geology could actually tell you where this was going to happen that this change was made," says Jones, who followed a similar path toward legislative advocacy work. "It was Northridge that pushed me into it, and San Fernando that pushed Clarence into it."
Later, Allen helped lobby for the formation of the National Earthquake Hazards Reduction Program (NEHRP), ultimately created by Congress in 1977 to reduce the loss of life and property caused by earthquakes through improved design and construction, emergency preparedness plans, and education.
During the late 1970s, the U.S. federal government funded efforts to determine whether it was possible to predict earthquakes, spurred in part by the apparently successful prediction of the 1975 Haicheng earthquake in China. Based on changes in groundwater and soil elevations, Chinese officials reportedly evacuated Haicheng in the morning of February 4, 1975. A magnitude-7.5 earthquake struck the region that evening.
At the time, there was little communication between scientists in the U.S. and China, so the event was shrouded in mystery. "We were told, this is your job: predict earthquakes. And nobody knew how to do it," says Thomas Heaton (PhD '78), professor of engineering seismology, emeritus. "We'd have arguments about whether it was even possible."
After thinking about the problem long enough to realize that it was not feasible, researchers moved from trying to predict earthquakes to trying to better understand the physics that govern them.
Allen was involved in the research, helping to establish the California Earthquake Prediction Evaluation Council, but remained agnostic. "We had some people who were true believers, and some who were true skeptics, but Clarence was just, 'let's just look and see where the data is,'" Heaton says.
Allen became one of the first Western scientists to travel to China, where he studied the country's earthquake prediction program. He ultimately concluded that while there had been some physical signs of the Haicheng quake before it occurred, luck had played a major role in the event, as the Chinese had also made a lot of predictions that had not panned out.
"One of the discouraging things has been that the more we look at earthquakes, the more we realize how different they are from one to the next," Allen said of the experience. "Although that's scientifically exciting, that's not very encouraging from the point of view of prediction. Because the more different earthquakes are from one to the next, the less likely it is that they're going to have common kinds of physical precursors."
The attempts at predicting earthquakes attracted the attention of Hollywood. In 1974, Charlton Heston starred in a move titled Earthquake, about a fictional temblor that wreaks havoc in Los Angeles. "The guys who wrote the movie based the scientists on the Caltech Seismo Lab," Heaton recalls. "At the beginning, for dramatic effect, they had a professor modeled after Clarence exploring geology in the field across the San Andreas Fault. And there's a foreshock, and a trench collapses, and kills this professor. So, according to Hollywood, Clarence died in '74," Heaton says with a laugh.
Former colleagues remember Allen as a hard worker, dedicated to his research, and always willing to mentor younger faculty.
"When I arrived here in 1983, Karen McNally [a seismologist who worked with Richter at Caltech and later founded the Institute of Tectonics at UC Santa Cruz] had just left, so I was the only woman with a PhD in the Seismo Lab," says Jones. "It could be awkward and sometimes I felt like I didn't belong, but Clarence was the most welcoming guy. He was a great scientist, but he was really also this incredible person. He was the human side of the Seismo Lab."
"Clarence was a friendly, considerate, and warm person," Kanamori says. "He was very popular among everyone."
He had a love of backpacking and the outdoors, which he shared with longtime friend and colleague Paul Jennings, professor of civil engineering and applied mechanics, emeritus. The two had shared interests in earthquakes and in fly fishing. They gave a joint Beckman Lecture in 1971 on the San Fernando earthquake, and took many fishing trips to the San Bernardino Mountains and elsewhere together. "Often, while having a lunch break while fishing, Clarence took pleasure in explaining the nature and geologic history of the rocks visible in the canyon walls," Jennings says.
Allen also hiked and fished with longtime head of the geological sciences division Robert Sharp, who had built a cabin in Montana near Yellowstone National Park.
He served as president of the Seismological Society of America as well as of the Geological Society of America, and was a member of numerous other professional societies, including the American Association for the Advancement of Science and the American Geophysical Union. He was elected to the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences.
Allen retired from Caltech in 1990, and was awarded the Harry Fielding Reid Medal of the Seismological Society of America in 1996. Though he purchased a home on the coast of Oregon that he had intended to retire to, he remained in Pasadena for the rest of his life and returned to the Seismo Lab just about every day to have coffee and discuss earthquake science with his former colleagues until a few years before his death.
"I saw him almost every day, and had many discussions with him on many earthquakes," Kanamori says. "His stories based on his extensive field experience in California, the Philippines, Chile, China, and Japan helped me a great deal in my seismological work. I very much miss the wonderful discussions with him during the coffee breaks."
This artcile was written by Robert Perkins.
How and when do mountains grow? It is tempting to think of mountain formation as something that takes place only extremely gradually, on timescales of tens of millions of years. One tectonic plate slowly pushes up against and slightly under another, until eventually up rises a mountain range. Of course, that picture is far too simplistic. We know, for example, that processes like erosion and earthquakes affect the way mountains grow.
Synthesizing data from more than 200 studies of the Himalaya, a team led by Caltech postdoctoral fellow Luca Dal Zilio has pieced together a far more complete picture of the mountain-building process. In a review study published in the journal Nature Reviews on May 2, Dal Zilio and his colleagues bridged timescales ranging from the seconds of shaking during an earthquake to the millions of years it takes for long-term tectonic processes to play out.
The researchers found that the Himalaya cycle through events that cause the range to rise and subside, rise and subside. "It's almost as though the range is breathing," says Dal Zilio. "However, the rising events over millions of years are larger than the rapid subsidence events during earthquakes. In the long run, this process leads to the growth of the Himalayan range."
The researchers focused on the wealth of geological, geophysical, and geodetic data that came out of the devastating 2015 Gorkha earthquake in Nepal and its aftershocks. For example, using radar images from satellites, scientists previously found that Mount Everest dropped by about a meter during the magnitude 7.8 temblor. But in the months following that event, scientists showed that the mountain regained roughly 60 percent of that lost elevation.
Dal Zilio and his colleagues drew on observations from the last several decades from the Himalaya, such as the thickness of the crust at different locations and what is known about the geometry of the Main Himalayan Fault, the roughly 2,000-kilometer-long fault at the base of the mountains.
Developing an understanding of how the Himalaya grow and change with time and how its earthquake cycle is affected is particularly important given the activity of the Main Himalayan Fault and its history of producing major earthquakes (some as large as magnitude-8.8) that affect one of the most populated regions on Earth.
The new Nature Reviews paper is titled "Building the Himalaya from tectonic to earthquake scales." Dal Zilio's co-authors on the paper are György Hetényi of the Institute of Earth Sciences at the University of Lausanne, in Switzerland; Judith Hubbard (BS '05) of the Earth Observatory of Singapore and Nanyang Technological University in Singapore; and Laurent Bollinger of the Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA) in Arpajon, France.
Dal Zilio's research at Caltech is supported by the Cecil and Sally Drinkward Fellowship.
Please read the full article written by Kimm Fesenmaier here.
A vast network of more than a million kilometers of fiber optic cable lies at the bottom of Earth's oceans. In the 1980s, telecommunication companies and governments began laying these cables, each of which can span thousands of kilometers. Today, the global network is considered the backbone of international telecommunications.
Scientists have long sought a way to use those submerged cables to monitor seismicity. After all, more than 70 percent of the globe is covered by water, and it is extremely difficult and expensive to install, monitor, and run underwater seismometers to keep track of the earth's movements beneath the seas. What would be ideal, researchers say, is to monitor seismicity by making use of the infrastructure already in place along the ocean floor.
Previous efforts to use optical fibers to study seismicity have relied on the addition of sophisticated scientific instruments and/or the use of so-called "dark fibers," fiber optic cables that are not actively being used.
Now Zhongwen Zhan (PhD '13), assistant professor of geophysics at Caltech, and his colleagues have come up with a way to analyze the light traveling through "lit" fibers—in other words, existing and functioning submarine cables—to detect earthquakes and ocean waves without the need for any additional equipment. They describe the new method in the February 26 issue of the journal Science.
During the nine months of testing reported in the new study (between December 2019 and September 2020), the researchers detected about 20 moderate-to-large earthquakes along the Curie Cable, including the magnitude-7.7 earthquake that took place off of Jamaica on January 28, 2020.
The new Science paper is titled "Optical polarization-based seismic and water wave sensing on transoceanic cables." Zhan's co-authors on the paper include Caltech graduate student Jorge C. Castellanos (MS '18); Google researchers Mattia Cantono, Valey Kamalov, Rafael Muller, and Shuang Yin; and Antonio Mecozzi of the University of L'Aquila in Italy.
The research at Caltech was funded by the Gordon and Betty Moore Foundation.
Please read the full article written by Kimm Fesenmaier here.
Just seconds after 6 a.m. on February 9, 1971, a 12-mile section of an under-appreciated fault along the San Gabriel Mountains suddenly and dramatically slipped. The entire Los Angeles region was rattled, but the shaking was particularly violent in the northeastern corner of the San Fernando Valley. By its end, two large hospitals (including one that was just months old) lay destroyed, powerlines had fallen, gas lines had exploded, freeway overpasses had collapsed, and many older buildings were damaged beyond repair. In the end, 65 people lost their lives, more than 2,000 other individuals were injured, and more than $500 million in property damage was apparent.
The quake struck at the end of a period of significant urban expansion in Los Angeles, when the region's first tall buildings had recently been constructed. One of the requirements for building such tall structures had been to keep a record of the shaking they experienced during earthquakes. As a result, the San Fernando earthquake was the first that was well-recorded by dozens of nearby seismometers.
"This was the first time we really had a glimpse of what the shaking was like around a major earthquake," explains Heaton. "It allowed us to really begin to understand what the earthquake process was like."
There was also a new realization among scientists after the 1971 earthquake that the thrust faults along the mountain ranges to the north of the L.A. region, such as the San Fernando and Sierra Madre faults, could produce large-magnitude quakes.
Equally important after the quake, Heaton says, was the great sense among earthquake scientists and engineers that monitoring and reporting systems had to be improved. When the San Fernando quake hit, it knocked out power to most of the L.A. region. Caltech's Seismological Laboratory normally received records of shaking via the telephone lines, but those were down as well.
Immediately after the 1971 earthquake, the U.S. Geological Survey (USGS), which had been operating in the Bay Area, was told to set up shop in Southern California.
Caltech welcomed the USGS with open arms, and together, Caltech researchers and the USGS have put many systems in place to reveal where the shaking was during an earthquake and its strength. Now, those systems are so fast that Southern California has an earthquake early warning system that can warn that shaking is on its way.
Another major piece of the developments following the 1971 earthquake was the creation by the federal government in 1977 of a multi-agency program called the National Hazards Earthquake Reduction Program (NHERP).
For the public, perhaps the most important outcomes of the 1971 San Fernando event were the laws and changes to building codes that were put into place to make buildings safer during major earthquakes.
Other changes took a bit longer. During the quake, the San Fernando Fault actually came to the surface of the earth and tore through people's houses. Prior to the event there was nothing to prevent builders from constructing homes and businesses directly on top of active fault lines.
After the 1971 earthquake, Clarence Allen (MS '51, PhD '54), the late Caltech geologist and geophysicist, went to Sacramento and explained to legislators that geologists know where the active faults are and that an earthquake like San Fernando would certainly happen again in California. In 1972, the California legislature passed the Alquist-Priolo Earthquake Fault Zoning Act, which prohibits building across active faults. "It was really because of Clarence spending the time and the effort to help people understand that geology could actually tell you where this was going to happen that this change was made," says Jones.
It took a lot more fighting and time to get the City of Los Angeles to require a change that seismologists identified as sorely needed after the 1971 earthquake: the requirement to retrofit unreinforced masonry buildings. During the earthquake, many of these unreinforced buildings suffered damage, including tragic collapses at a homeless shelter in downtown Los Angeles and at the Veterans Administration Hospital in San Fernando, where 49 people died. In 1981, the city required that about 10,000 unreinforced buildings either be retrofitted or torn down. In 1986, the state of California passed a law requiring that all jurisdictions catalog unreinforced masonry buildings and develop retrofitting programs.
Please read the full article by Kimm Fesenmaier here.
Clarence Allen (MS '51, PhD '54), professor of geology and geophysics, emeritus, and a prominent seismologist, passed away on January 21, 2021. He was 96 years old.
Allen was born on February 15, 1925, in Palo Alto, California. He earned his bachelor's degree in physics from Reed College in 1949, and his master's and doctoral degrees from Caltech in 1951 and 1954, respectively. After he began his studies at Reed in 1942, Allen spent three years (1943–46) in the U.S. Army Air Corps before returning to finish his undergraduate degree.
Once he earned his PhD, Allen spent a year as an assistant professor at the University of Minnesota. Allen then joined Caltech's faculty in 1955 as an assistant professor. He became an associate professor in 1959 and full professor in 1964. He also served as the interim director of Caltech's Seismological Laboratory from 1965–67 and was acting chairman of what was at the time called Caltech's Division of Geology (now the Division of Geological and Planetary Sciences), from 1967–68.
During his career, he was most known for his contributions to the evaluation of seismicity and fault movements in regions where earthquakes are common.
He served as president of the Seismological Society of America as well as of the Geological Society of America, and was a member of numerous other professional societies, including the American Association for the Advancement of Science, and the American Geophysical Union. He was elected to the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences.
Allen retired from Caltech in 1990, and was awarded the Harry Fielding Reid Medal of the Seismological Society of America in 1996.
A full memorial story will be posted at a later date.
Congratulations to Nadia Lapusta for being selected as an AGU Fellow (https://eos.org/agu-news/2020-class-of-agu-fellows-announced). Nadia, a member of the Seismo Lab, is the Lawrence A. Hanson, Jr. Professor of Mechanical Engineering and Geophysics at Caltech.
Nadia is an internationally recognized expert on the physics of earthquakes. With her many students and post-docs, Nadia has made ground-breaking progress in understanding earthquake sequences through the study of crustal faults, like the San Andreas Fault, by developing and applying multi-time-scale models that include fault nucleation, dynamic rupture along the fault, energy dissipation, and seismic wave propagation. These extraordinarily detailed and computationally challenging models have uncovered how rupture is governed by friction and other fault properties, while optimizing the physics against geophysical observations, like regional geodetic and seismic observations.
For a nice description of Nadia's work in computational studies of earthquake processes, see the breakthrough article here.
The 2019 Ridgecrest earthquake sequence has revealed areas of the Los Angeles basin where the amplification of shaking of high-rise buildings is greatest, according to a new report in Seismological Research Letters.
The 6 July 2019 magnitude 7.1 earthquake, located 200 kilometers (124 miles) north of Los Angeles, did not cause structural damage in the city. But there was significant shaking in some high-rise buildings in downtown Los Angeles—so much that their residents reported feeling nauseous from the movement.
All buildings have a natural "vibration" or sway, which civil engineers and seismologists refer to as the building's longest natural period since it marks the amount of time it takes for a building to move back and forth in one cycle in a plane parallel to the ground. High-rise buildings of 15 floors or more, long-span bridges and large diameter fuel storage tanks, among other structures, typically have natural periods of three seconds or more.
Using data from a network of seismic stations across the L.A. basin Caltech scientists (including) Monica Kohler and Filippos Filippitzis of the Department of Mechanical and Civil Engineering,Tom Heaton, Rob Clayton and Richard Guy of the Seismological Laboratory, Julian Bunn of the Department of Astronomy, and Mani Chandy of Computing and Mathematical Sciences) determined that long-period buildings experienced the most amplification of shaking from the Ridgecrest earthquake. The study used data from the densely spaced
Community Seismo Network.
But the effect was not the same throughout the basin. At six- and eight-second periods, the maximum amplification occurred in the western part of the L.A. basin and the south-central San Fernando Valley.
In the event of a future earthquake similar to Ridgecrest, a high-rise building in those areas could experience shaking four times larger than a building located in downtown Los Angeles, the researchers concluded. In a 52-story building, this means that the upper floors might sway back and forth as much as one meter (about 3 feet)—or as much as two meters in a magnitude 7.6 earthquake, straining the building's structural integrity.
Additional details can be found here.
Approximately 20,000 earthquakes occur each year, or 55 per day, according to the National Earthquake Information Center catalog. Most are so small that humans cannot feel them. Nonetheless, over the past 50 years, earthquakes and the tsunamis and landslides that resulted from them have contributed to millions of injuries and deaths and more than $1 trillion in damage. For nearly a century, Caltech scientists and engineers have led the world in earthquake measurement and monitoring. By informing preparedness and response initiatives, and pioneering innovations in early warning, their work aims to reduce the human toll of these natural disasters. Learn more about earthquake science and engineering.
Click here to read the articles on Caltech Science Exchange.
Despite climate change being most obvious to people as unseasonably warm winter days or melting glaciers, as much as 95 percent of the extra heat trapped on Earth by greenhouse gases is held in the world's oceans. For that reason, monitoring the temperature of ocean waters has been a priority for climate scientists, and now Caltech researchers have discovered that seismic rumblings on the seafloor can provide them with another tool for doing that.
They do this by listening for the sounds from the many earthquakes that regularly occur under the ocean, says Jörn Callies, assistant professor of environmental science and engineering at Caltech and study co-author.
Wenbo Wu, postdoctoral scholar in geophysics and lead author of the paper, explains that when an earthquake happens under the ocean, most of its energy travels through the earth, but a portion of that energy is transmitted into the water as sound. "These sound waves in the ocean can be clearly recorded by seismometers at a much longer distance than thunder — from thousands of kilometers away," Wu says. "Interestingly, they are even 'louder' than the vibrations traveling deep in the solid Earth, which are more widely used by seismologists."
"The key is that we use repeating earthquakes—earthquakes that happen again and again in the same place," he says. "In this example we're looking at earthquakes that occur off Sumatra in Indonesia, and we measure when they arrive in the central Indian ocean. It takes about a half hour for them to travel that distance, with water temperature causing about one-tenth-of-a second difference. It's a very small fractional change, but we can measure it."
"We are using small earthquakes that are too small to cause any damage or even be felt by humans at all," Wu says. "But the seismometer can detect them from great distances, thus allowing us to monitor large-scale ocean temperature changes on a particular path in one measurement."
"The ocean plays a key role in the rate that the climate is changing," Callies says. "The ocean is the main reservoir of energy in the climate system, and the deep ocean in particular is important to monitor. One advantage of our method is that the sound waves sample depths below 2,000 meters, where there are very few conventional measurements."
The paper describing the research, titled, "Seismic Ocean Thermometry," appears in the September 18 issue of Science. Co-authors are Wenbo Wu, postdoctoral scholar in geophysics; Zhongwen Zhan (PhD '13), assistant professor of geophysics; and Shirui Peng, graduate student in environmental science and engineering, all from Caltech; and Sidao Ni (MS '98, PhD '01) of the Institute of Geodesy and Geophysics at the Chinese Academy of Sciences.
Click here to read the full article written by Emily Velasco.
Donald V. Helmberger, who ran the Caltech Seismological Laboratory from 1998 to 2003, passed away on August 13 at the age of 82.
Helmberger, Smits Family Professor of Geophysics, Emeritus, was born on January 23, 1938. He grew up in Perham, Minnesota, and earned his bachelor's degree from the University of Minnesota in 1961. During his undergraduate studies, he connected with alumnus George Shor (BS '44, MS '48, PhD '54) of the Scripps Institution of Oceanography, who took Helmberger on a research cruise to Alaska in the summer of 1961 to conduct seismic studies of the oceanic crust in the Bering Sea. This first foray into seismology research changed the course of Helmberger's academic career: although he was originally interested in physics, he shifted his focus to geophysics when he entered graduate school at UC San Diego. He earned a master's degree in 1965 and a doctorate degree in 1967.
After he earned his PhD, Helmberger took a position as a research associate at MIT and then worked as an assistant professor at Princeton University. He returned to California when he was offered a job in the Caltech Seismological Laboratory by Don Anderson, the lab's director from 1967 to 1989; Helmberger recalled in a 1999 oral history that he was intrigued by the Seismological Laboratory because it was one of only two places at the time that maintained large earthquake catalogs.
Helmberger joined the Caltech faculty as an assistant professor in 1970, became an associate professor in 1974, and a full professor in 1979. In 2000, he was named Smits Family Professor of Geophysics.
On the morning of February 9, 1971, the magnitude-6.5 San Fernando earthquake shook him out of his bed in Altadena. The event kindled his interest in modeling earthquakes to understand the physical forces that drive them. At the time, earthquake models typically focused on long-period seismological waves, which reveal how Earth vibrates as a whole. Helmberger and his colleagues pioneered the development of models based on the short-period waves that actually cause damage. These models revealed details about the earthquake itself, such as the complexity of the fault rupture and its depth below ground.
Helmberger's primary research interests involved seismic-wave propagation and the use of waveforms to recover information about earthquake characteristics as well as the earth's structure. He discovered ultralow velocity zones (ULVZs), which are unusual masses that lurk at the base of the earth's mantle, just above the core. ULVZs, which are so-named because they significantly slow the seismic waves that pass through them, have been observed under the Pacific Rim, North America, Europe, and Africa.
In 1997, Helmberger became the first recipient of the American Geophysical Union's Inge Lehmann Medal, and he was named to the National Academy of Sciences in 2004. He became an emeritus professor in 2017.
Geoscience students at Caltech will now have access to industry standard seismic data processing software, thanks to a $248,310 donation from IHS Markit (Nasdaq: INFO), a world leader in critical information, analytics and solutions. Caltech Seismological Laboratory professor Joann Stock has been awarded three Educational Network Licenses for each of the following IHS Markit software products: Kingdom Geoscience Bundle, LoadPAK add-on, and Petrophysics.
The products will be used by Professor Joann Stock and PhD graduate students doing research using multichannel seismic data (SEG-Y files). They will be used for two studies: (1) analysis and interpretation of MCS data collected during Caltech class Ge211 (Marine Geophysics) south of New Zealand in 2018; and (2) results of drilling at 25 sites on IODP Expedition 385 in the Gulf of California, in fall 2019, where crossing MCS lines were previously obtained and used to choose drilling locations. For the latter project, we will use the downhole geophysical logs, shipboard petrophysical measurements on the core samples, and core-log-seismic integration to ground-truth the characterization of the seismic stratigraphy and refine the processing of the MCS data that was collected prior to drilling the holes.
Kingdom™ integrates geoscience, geophysics and engineering into a single, easy-to-use software solution, enabling asset teams to make confident and faster decisions from exploration to completion. Our solutions are simplified, giving you access to advanced geoscience/scientific tools that are affordable, easy to learn and install and come with excellent support and training.
For more on IHS Markit Educational Licenses click here.
A naturally occurring injection of underground fluids drove a four-year-long earthquake swarm near Cahuilla, California, according to a new seismological study that utilizes advances in earthquake monitoring with a machine-learning algorithm.
The study, published on June 18 in the journal Science, illustrates an evolving understanding of how fault architecture governs earthquake patterns. "We used to think of faults more in terms of two dimensions: like giant cracks extending into the earth," says Zachary Ross, assistant professor of geophysics and lead author of the Science paper. "What we're learning is that you really need to understand the fault in three dimensions to get a clear picture of why earthquake swarms occur."
Typically, faults are thought to either act as conduits for or barriers to the flow of underground fluids, depending on their orientation to the direction of the flow. While Ross's research supports that generally, he and his colleagues found that the architecture of the fault created complex conditions for underground fluids flowing within it.
The researchers noted the fault zone contained undulating subterranean channels that connected with an underground reservoir of fluid that was initially sealed off from the fault. When that seal broke, fluids were injected into the fault zone and diffused through the channels, triggering earthquakes. This natural injection process was sustained over about four years, the team found.
"These observations bring us closer to providing concrete explanations for how and why earthquake swarms start, grow, and terminate," Ross says.
Next, the team plans to build off these new insights and characterize the role of this type of process throughout the whole of Southern California.
Yes, there’s a prize for the most beautiful flower-filled float in the Rose Parade each year, but how about a prize for the most ground-shaking marching band? According to a new study, the 2020 honors go to the Southern University and A&M College, followed closely by the hometown Pasadena City College Honor band.
These bragging rights and other interesting signatures of the Rose Parade were captured by fiber optic telecommunications cable lying below the parade route. In Seismological Research Letters, Zhongwen Zhan of the California Institute of Technology and colleagues describe how they converted these dark fibers within cables into a dense seismic array.
The technique, called distributed acoustic sensing (DAS), uses the tiny internal flaws in a long optical fiber as thousands of seismic sensors. An instrument at one end of the fiber sends laser pulses down the cable that are reflected off the fiber flaws and bounced back to the instrument.
For the Rose Parade project, Zhan and colleagues examined data from a 2.5-kilometer (1.6 mile) stretch of cable under the parade route that contained about 400 seismic sensors. In this case, the disturbance to the cables was the compression and flexure of the roads by parade participants.
"The main goal of the Pasadena Array is to detect small earthquakes and image the geological structure underneath the city. It has been operating only since November 2019, so we actually do not have any good-sized earthquake in the city yet," explained Zhan. "The Rose Parade, as a well-controlled event—no other traffic except the parade, traveling all in one direction at almost constant speed—provides a rare opportunity for network calibration."
Their seismic readout "turned out to be quite broadband," Zhan said. The array captured the distinct signals of zig-zagging police motorcycles clearing the route, the bend of the road as heavy floats weighing 16,000 to 18,000 kilograms (17.6 to 19.9 tons) passed overhead, and a series of harmonic frequencies that corresponds to the even stepping of the marching bands. The "heaviest" float measured in this way was the Amazon studios float, which contained a bus and rocket mounted on a truck.
“This project inspires us that in the future we will probably use heavy vehicles for calibrations of DAS arrays in other cities", Zhan says.
The NSF Graduate Research Fellowship Program (GRFP) helps ensure the vitality of the human resource base of science and engineering in the United States and reinforces its diversity. The program recognizes and supports outstanding graduate students in NSF-supported science, technology, engineering, and mathematics disciplines who are pursuing research-based master's and doctoral degrees at accredited United States institutions.
As the oldest graduate fellowship of its kind, the GRFP has a long history of selecting recipients who achieve high levels of success in their future academic and professional careers. The reputation of the GRFP follows recipients and often helps them become life-long leaders that contribute significantly to both scientific innovation and teaching.
Congratulations Jimmy!
Celeste Labedz heard a sound like thunder roll across the ice. She was standing on Alaska’s Taku Glacier, a vast field of snow-smothered ice between towering mountains, when the icequake began: a short-lived seismic tremor caused by the glacier’s sudden movement. Immediately she scrambled for her notebook and jotted down the time. Labedz, a graduate student at the California Institute of Technology, would check that time against data from a fiber-optic cable she and her colleagues had just deployed to study such quakes—a promising new method that is shaking up geology and adjacent fields.
Information travels through a fiber-optic cable via pulses of laser light, most of which moves directly through the hair-thin glass threads. But inevitably a small amount hits microscopic flaws in the cable and scatters back toward the source. This reflection varies when the cable stretches or bends because of ground vibrations, such as those from an earthquake or even a passing truck, and scientists can monitor changes in the backscattered light to quantify those movements. First developed by the petroleum industry a decade ago, this technique—known as distributed acoustic sensing (DAS)—has recently infiltrated the sciences.
One major advantage to DAS is that fiber-optic cables can be many kilometers long, and a single one can act like a network of thousands of sensors covering every meter along its path. A second benefit is that fiber-optic cables already crisscross the world.
Then there is the glacier work, for which Labedz and her colleagues have transformed a single cable into 3,000 seismic sensors. Early results show a five-hour stretch with 100 icequakes—many likely caused by meltwater forcing open crevasses within the glacier. Labedz’s academic adviser Zhongwen Zhan, a seismologist at Caltech, hopes to one day place permanent fiber-optic cables in Greenland or Antarctica to help researchers learn more about how glacier melt driven by climate change contributes to sea-level rise.
And Zhan has an even larger dream: to build the equivalent of a million-sensor array in California using about 1,000 kilometers of dark fiber. He has already converted 37 kilometers into a permanent seismic network below Pasadena and would like to do the same in other cities across the state. The data could reveal vulnerabilities in cities’ infrastructure and could help alert citizens the instant an earthquake begins. “This is going to be a huge help in terms of preparing the community,” Zhan says. At the moment, scientists cannot predict earthquakes—but a better understanding of the precursory shocks that occasionally lead up to a main quake could only help.
Click here to read the full article.
Frank Press, former director of the Caltech Seismological Laboratory, died on January 29 at the age of 95.
Press, who was a professor of geophysics at Caltech for 10 years starting in 1955 and ran the Seismological Laboratory from 1957 to 1965, later served as chief science advisor to President Jimmy Carter and then as president of the National Academy of Sciences (NAS) for 12 years. He helped develop innovative quantitative approaches to seismology, bringing computer technology into the field to help monitor and measure earthquakes.
Colleagues remember Press as a serious, brilliant researcher, who energetically pushed new projects and approaches. He arrived at Caltech at a time when the Seismo Lab was dominated by three titans of seismology: Charles Richter (PhD '28), Beno Gutenberg, and Hugo Benioff (PhD '35). Gutenberg had been the lab's director since 1946 and worked with Richter on the creation of a logarithmic scale for describing the strength of an earthquake. Hugo Benioff designed a simple, reliable, and sensitive strain seismometer that allowed the very subtle long-period motions of the earth to be measured and which would later emerge as key to Press's Caltech contributions.
"Caltech, with the Seismo Lab, had already emerged as the undisputed leader in earthquake research when Frank joined the Lab," says Mike Gurnis, the John E. and Hazel S. Smits Professor of Geophysics and current director of the laboratory.
In the 1950s and '60s, with the Cold War reaching a fever pitch, seismologists like Press began using seismometers to detect and measure nuclear blasts. Press led a U.S. delegation that participated in nuclear test-ban talks in Geneva in 1960.
After 10 years in Pasadena, Press left Caltech for MIT. His departure from Caltech coincided with the arrival of then-research fellow Hiroo Kanamori, who was the Seismo Lab's director from 1990–98.
"Rather interestingly, when I arrived at Caltech I was given Press's office in the North Mudd Building with his name plate still on the door," says Kanamori, who is now John E. and Hazel S. Smits Professor of Geophysics, Emeritus. "Although Frank was no longer at the Seismo Lab, his influence on the research atmosphere was quite evident."
Click here to read the full article.
Zhichao Shen received the Outstanding Student Presentation Award from the 2019 AGU Fall Meeting held in San Francisco, CA, December 9-13, 2019. The title of the study is “Small-scale instraslab heterogeneity constrained from inter-source interferometry".
The Outstanding Student Presentation Awards (OSPAs) promote, recognize and reward undergraduate, Master's and PhD students for quality research in the Earth and space sciences. It is a great honor for young scientists at the beginning of their careers. The process relies entirely on volunteer judges. Typically the top 3-5% of presenters in each Section are awarded an OSPA and all judged students are provided feedback.
Congratulations Zhichao!
Click here for information on the AGU Student Presentation Award.
An international team of geoscientists led by Caltech has used fiber optic communications cables stationed at the bottom of the North Sea as a giant seismic network, tracking both earthquakes and ocean waves.
The project was, in part, a proof of concept. Oceans cover two-thirds of the earth's surface, but placing permanent seismometers under the sea is prohibitively expensive. The fact that the fiber network was able to detect and record a magnitude-8.2 earthquake near Fiji in August 2018 proves the ability of the technology to fill in some of the massive blind spots in the global seismic network, says Caltech graduate student Ethan Williams (MS '19). Williams is the lead author of a study on the project that was published by Nature Communications on Dec. 18.
The project relies on a technology called distributing acoustic sensing, or DAS. DAS was developed for energy exploration but has been repurposed for seismology. DAS sensors shoot a beam of light down a fiber optic cable. Tiny imperfections in the cable reflect back miniscule amounts of the light, allowing the imperfections to act as "waypoints." As a seismic wave jostles the fiber cable, the waypoints shift minutely in location, changing the travel time of the reflected light waves and thus allowing scientists to track the progression of the wave.
"Seafloor DAS is a new frontier of geophysics that may bring orders-of-magnitude more submarine seismic data and a new understanding of the deep Earth's interior and major faults," says Zhan, assistant professor of geophysics and coauthor of study.
For the North Sea project, Williams, Zhan, and their colleagues employed a 40,000-meter section of fiber optic cable that connects a North Sea wind farm to the shore. "With the flip of a switch, we have an array of 4,000 sensors that would've cost millions to place," Williams says.
The paper is titled "Distributed sensing of microseisms and teleseisms with submarine dark fibers." Co-authors include María Fernández-Ruiz and Regina Magalhaes of the University of Alcalá; Roel Vanthillo of Marlinks in Belgium; and Hugo Martins of the Institute of Optics in Spain. Funding for this research came from Caltech; JPL, which Caltech manages for NASA; the National Science Foundation; the Spanish Ministerio de Ciencia; Innovacíon y Universidades; and the European Union's Horizon 2020 Research and Innovation Programme.
Click here to read full article by Robert Perkins.
The work will take advantage of two currently unused—or "dark"—strands of Pasadena's fiber optic cable that stretch in a large loop around the city. Using a couple strands of fiber to measure seismic activity will gather data equivalent to more than 30,000 seismometers, while only 11 traditional seismometers exist within the city limits today. Zhongwen Zhan, assistant professor of geophysics, will tap into the fiber network at the Seeley G. Mudd Building of Geophysics and Planetary Science on Caltech's campus on California Boulevard.
Zhan will station two laser emitters that shoot beams of light through the cables. The cables have tiny imperfections every few meters that reflect back a minuscule portion of the light to the source, where it is tracked and recorded. In this manner, each imperfection acts as a trackable waypoint along the fiber optic cable. Seismic waves moving through the ground cause the cable to expand and contract slightly, which changes the travel time of light to and from these waypoints. Thus, the imperfections act like individual seismometers that allow seismologists to observe the motion of seismic waves.
"The City of Pasadena's fiber optics paired with Caltech's research will produce a tremendous amount of data that will help our efforts to prepare, educate, and communicate the impacts of earthquakes in our community," says Phillip Leclair, chief information officer for the City of Pasadena. "Measuring seismic activity with fiber will give officials impact and damage predictions by neighborhood—a huge benefit for public safety and disaster recovery."
"The Pasadena project is an important step forward in lighting up dark fiber throughout Southern California and achieving our vision of a seismic monitoring system equivalent to having a million seismometers placed throughout the region," says Mike Gurnis, director of Caltech's Seismological Laboratory and John E. and Hazel S. Smits Professor of Geophysics. "This will be a leap forward in our ability to monitor the subsurface in much greater detail. We are particularly grateful for the support shown by the City of Pasadena. This advancement would never have happened without them."
Click here to read full article by Robert Perkins.
Caltech's Rob Clayton is preparing to launch a project to blanket the Los Angeles Basin with 25 seismic sensors per square mile, gathering high-resolution data at an unprecedentedly wide scale over the 800-square-mile area.
The 3-D passive seismic survey will be a collaboration with seismic exploration company Sisprobe and geophysical consulting firm LA Seismic, and would serve the dual purposes of seismic hazard assessment and identifying areas for improving the resiliency of critical infrastructure.
"The sensors that we use for these surveys were developed for natural resources exploration, but also reveal a great deal about low-level seismicity and seismic hazard," says Clayton, professor of geophysics. "This is an example of how academia can partner with industry to launch large-scale projects."
The end result would be a uniform and detailed ground-motion map revealing the faults beneath the LA Basin, and would be kept in an open-source database.
Clayton has used similar surveys on a smaller scale, blanketing Long Beach, Santa Fe Springs, West Orange County, and South West Los Angeles with thousands of sensors in the past. Those highly localized efforts, conducted over the past eight years, revealed previously undiscovered faults, folds in the earth, and creeping zones.
Click here to read full article by Robert Perkins.
The study, a comprehensive analysis of the Ridgecrest Earthquake Sequence by geophysicists from Caltech and JPL, will be published in Science on October 18. The Ridgecrest earthquake sequence included a magnitude-6.4 foreshock on July 4, followed by a magnitude-7.1 mainshock nearly 34 hours later, and more than 100,000 aftershocks.
"This was a real test of our modern seismic monitoring system," says Zachary Ross, assistant professor of geophysics at Caltech and lead author of the Science paper. "It ended up being one of the best-documented earthquake sequences in history and sheds light on how these types of events occur."
The team drew on data gathered by orbiting radar satellites and ground-based seismometers to piece together a picture of an earthquake rupture that is far more complex than found in models of many previous large seismic events.
"We actually see that the magnitude-6.4 quake simultaneously broke faults at right angles to each other, which is surprising because standard models of rock friction view this as unlikely," Ross says. "It is remarkable that we now can resolve this level of detail."
Also noteworthy is that the rupture ended just a few kilometers shy of the nearby Garlock Fault, which stretches more than 300 kilometers across Southern California on the northern boundary of the Mojave Desert. The fault has been relatively quiet for the past 500 years, but the strain placed on the Garlock Fault by July's earthquake activity triggered it to start creeping. Indeed, the fault has slipped two centimeters at the surface since July, the scientists say.
Click here to read full article by Robert Perkins.
Richard H. Jahns Teaching Award, recognizing outstanding achievement as a graduate teaching assistant.
Thanks to their, dedication, passion, preparedness, understanding and patience. Recipients are described as the best TA's their students have known.
Zach, recently appointed as an Assistant Professor of Geophysics at Caltech, is at the forefront of developing automated methods for extracting geophysical information from large seismic datasets to investigate earthquake processes and fault properties. Recently, Ross identified nearly two million previously unidentified tiny earthquakes that occurred between 2008 and 2017 by pouring through 10 years' worth of Southern California seismic data (https://www.caltech.edu/about/news/scientists-identify-almost-2-million-previously-hidden-earthquakes). In recognition of his many scientific accomplishments as a young scientist, Zach will receive the prestigious Keiiti Aki Award at the Fall AGU Meeting in San Francisco.
Congratulations Zach!
Click here for the full list of AGU awadees and named lecturers.
Seismologists Monitor Ridgecrest Aftershocks Using Novel Fiber Optic NetworkSeismologists from Caltech are using fiber optic cables to monitor and record the aftershocks from the 2019 Ridgecrest earthquake sequence in greater detail than previously possible. Thousands of tiny aftershocks are occurring throughout the region each day, an unprecedented number of which will now be able to be tracked and studied.
The project was launched just days after the two large earthquakes struck the Ridgecrest area. Zhongwen Zhan called around, searching for unused fiber optic cable that would be long enough and close enough to the seismically active region to be useful. Eventually, the manager of the Inyokern Airport, Scott Seymour (who had also offered the use of the fiber network around the airport), connected Zhan with Michael Ort, the chief executive officer of the California Broadband Cooperative's Digital 395 project.
Digital 395 has offered to let Zhan use three segments of its fiber optic cable: 10 kilometers from Ridgecrest to the west, and two sections both to the north and south of Olancha, near which there was intense seismic activity triggered by the M7.1 quake.
Though the Ridgecrest seismic monitoring will be temporary, Zhan and his colleagues hope to establish similar systems permanently in key cities throughout Southern California. This work began with a pilot project in 2018 involving the Caltech Seismological Laboratory and the City of Pasadena to use a portion of the city's dark fiber to monitor temblors in the area.
Cclick here to read the full article.
 copy.jpg)
What is it Like to be a Caltech Seismologist During a Big Quake?When an earthquake strikes, seismologists at Caltech's Seismological Laboratory spring into action.
An arm of Caltech's Division of Geological and Planetary Sciences (GPS), the Seismo Lab is home to dozens of seismologists who collaborate with the United States Geological Survey (USGS) to operate one of the largest seismic networks in the nation.Together, they analyze data to provide the public with information about where the quake occurred and how big it was. That information not only helps first responders, but feeds into the scientific understanding on earthquakes and when and where the next big quakes are likely to strike.
After the two largest Ridgecrest earthquakes on July 4 and 5 (Magnitude 6.4 and 7.1, respectively), Caltech staff seismologist Jen Andrews was part of the Seismo Lab team that rushed to respond. Recently, she described that experience.
Cclick here to read the full article.
Congratulations to the 2019 GPS Division Graduates in the Seismo Lab Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates pictured (from left to right) Rachel Morrison and Vishagan Ratnaswamy.
Far from being static features of the landscape, glaciers are dynamic rivers of ice, flowing and carving earth beneath them in a diverse range of rates. There are fast-flowing glaciers, slow or stagnant glaciers, and surging glaciers that periodically accelerate and slow down again.
It’s long been thought, Zhan notes, that liquid water at the base of glaciers might be acting as a lubricant, speeding glaciers up and along, but it is difficult to fully characterize what is taking place under many meters of ice. In a recent study published in Geophysical Research Letters, Zhan details the results of a new approach that offers a work-around.
Zhan’s insight was to make use of two seismological stations set up astride the surging Bering Glacier in Alaska. Zhan examined station data for a 12-year period, which included a surge that lasted from 2008 to 2010, measuring changes in the speed of background seismic waves as they passed through the glacier. He found that waves slowed down during the surge, indicating they were traveling though softer material—water rather than ice or rock.
Zhan thinks that the bottom 10 or 20 meters of a glacier crack during a surge, with those cracks running perpendicular to the direction of the glacier’s flow. Water, he says, rather than simply pooling at the base of the ice, fills these cracks. Zhan measured two types of seismic waves, Rayleigh and Love waves, to reach this conclusion.
Zhan would also like to extend his technique in future studies, perhaps adding additional seismological stations at different orientations across the glacier to better test his hypothesis.
Click here to read the full article in EOS.
Pouring through 10 years' worth of Southern California seismic data with the scientific equivalent of a fine-tooth comb, Caltech seismologists have identified nearly two million previously unidentified tiny earthquakes that occurred between 2008 and 2017.
Their efforts, published online by the journal Science on April 18, expand the earthquake catalog for that region and period of time by a factor of 10—growing it from about 180,000 recorded earthquakes to more than 1.81 million. The new data reveal that there are about 495 earthquakes daily across Southern California occurring at an average of roughly three minutes apart. Previous earthquake cataloging had suggested that approximately 30 minutes would elapse between seismic events.
"It's not that we didn't know these small earthquakes were occurring. The problem is that they can be very difficult to spot amid all of the noise," says Zachary Ross, lead author of the study and postdoctoral scholar in geophysics, who will join the Caltech faculty in June as an assistant professor of geophysics. Ross collaborated with Egill Hauksson, research professor of geophysics at Caltech.
Click here to read the full article written by Robert Perkins.
The NSF Graduate Research Fellowship Program (GRFP) helps ensure the vitality of the human resource base of science and engineering in the United States and reinforces its diversity. The program recognizes and supports outstanding graduate students in NSF-supported science, technology, engineering, and mathematics disciplines who are pursuing research-based master's and doctoral degrees at accredited United States institutions.
As the oldest graduate fellowship of its kind, the GRFP has a long history of selecting recipients who achieve high levels of success in their future academic and professional careers. The reputation of the GRFP follows recipients and often helps them become life-long leaders that contribute significantly to both scientific innovation and teaching.
Congratulations Erin and Ethan!
Stacy Larochelle received the Outstanding Student Presentation Award from the 2018 AGU Fall Meeting held in Washington D.C. December 12-14, 2018. The title of the study is “Identification and extraction of seasonal geodetic signals due to surface load variations.”
The Outstanding Student Presentation Awards (OSPAs) promote, recognize and reward undergraduate, Master’s and PhD students for quality research in the Earth and space sciences. It is a great honor for young scientists at the beginning of their careers. The process relies entirely on volunteer judges. Typically the top 3-5% of presenters in each Section are awarded an OSPA and all judged students are provided feedback.
Congratulations Stacy!
Click here for information on the AGU Student Presentation Award.
The Caltech Science for March was held on Saturday, March 16 from 10am - 3pm on Beckman Mall. The event brought the local community and scientists together at Caltech to enjoy, share, and celebrate science. Seismo Lab students created an interactive earthquake booth which was enjoyed by all who attended.
The booth was manned by Seismo Lab graduate students and post docs, Voon Hui Lai, Leah Sabbeth, Valere Lambert, Celeste Labedz, Xin Wang and Sunny Park.
More photos from the Science for March event.
Q&A: Creating a "Virtual Seismologist"Understanding earthquakes is a challenging problem—not only because they are potentially dangerous but also because they are complicated phenomena that are difficult to study. Interpreting the massive, often convoluted data sets that are recorded by earthquake monitoring networks is a herculean task for seismologists, but the effort involved in producing accurate analyses could significantly improve the development of reliable earthquake early-warning systems.
A promising new collaboration between Caltech seismologists and computer scientists using artificial intelligence (AI)—computer systems capable of learning and performing tasks that previously required humans—aims to improve the automated processes that identify earthquake waves and assess the strength, speed, and direction of shaking in real time. The collaboration includes researchers from the divisions of Geological and Planetary Sciences and Engineering and Applied Science, and is part of Caltech's AI4Science Initiative to apply AI to the big-data problems faced by scientists throughout the Institute. Powered by advanced hardware and machine-learning algorithms, modern AI has the potential to revolutionize seismological data tools and make all of us a little safer from earthquakes.
Recently, Caltech's Yisong Yue, an assistant professor of computing and mathematical sciences, sat down with his collaborators, Research Professor of Geophysics Egill Hauksson, Postdoctoral Scholar in Geophysics Zachary Ross, and Associate Staff Seismologist Men-Andrin Meier, to discuss the new project and future of AI and earthquake science.
Click here to read the full article written by Elise Cutts.
ShakeAlert No Longer Just a PrototypeGovernment officials and Caltech scientists gathered at the Caltech Seismological Laboratory on October 17 to declare ShakeAlert—an earthquake early warning system for the three states along the West Coast—"open for business." West Coast's earthquake early warning system is still under construction but is available for public use.
Earthquake early warning systems like ShakeAlert consist of a network of sensors near faults that transmit signals to data-processing centers when shaking occurs. These data-processing centers use algorithms to rapidly determine the earthquake's location, magnitude, and the fault rupture length—determining the intensity of an earthquake and sending out an alert that can provide seconds or even minutes of warning. Paired with automated responses that will shut off gas before shaking starts, ShakeAlert could be instrumental in preventing the fires that typically damage cities after a major earthquake, Lucy Jones said.
Though only half of the sensor network that ShakeAlert will need has been built out so far—primarily around major metropolitan areas—the state of California and the federal government have allocated funding that should allow the rest of California's portion of the network to be constructed over the next two years, Given said. In addition, an upgrade to the software that processes data from the sensor networks was deployed on September 28. This new software should reduce the number of mistakes and missed alerts, making ShakeAlert more reliable. A key step now is for companies and institutions to help find ways to take advantage of these alerts to save lives, Doug Given said.
Earthquake early warning systems already exist in Mexico and Japan, which have experienced recent and devastating earthquakes. But it has been difficult to find the political will to spend millions of dollars developing a system for the U.S. West Coast, which is long overdue for a serious earthquake.
Over the past few years, ShakeAlert has detected thousands of earthquakes, including two that caused damage. It began sending alerts within four seconds of the beginning of the magnitude 5.1 La Habra earthquake in 2014, and gave users in Berkeley five seconds of warning before seismological waves arrived during the magnitude 6.0 South Napa earthquake, also in 2014. Beta-test users received these alerts as a pop-up on their computers; the pop-up displayed a map of the affected region as well as the amount of time until shaking would begin, the estimated magnitude of the quake, and other data.
Click here to read the full article written by Robert Perkins.
Experiments using Diamond Anvils Yield New Insight into the Deep EarthNearly 1,800 miles below the earth's surface, there are large odd structures lurking at the base of the mantle, sitting just above the core. These odd structures, known as ultra-low velocity zones (ULVZs), were first discovered in 1995 by Caltech's Don Helmberger. ULVZs can be studied by measuring how they alter the seismic waves that pass through them.
ULVZs are so-named because they significantly slow down the speeds of seismic waves; for example, they slow down shear waves (oscillating seismic waves capable of moving through solid bodies) by as much as 30 percent. ULVZs are several miles thick and can be hundreds of miles across. Several are scattered near the earth's core roughly beneath the Pacific Rim. Others are clustered underneath North America, Europe, and Africa.
Earth scientists at Caltech now say they know not just what ULVZs are made of, but where they come from. Using experimental methods at high pressures, the researchers, led by Professor of Mineral Physics Jennifer Jackson, have found that ULVZs consist of chunks of a magnesium/iron oxide mineral called magnesiowüstite that could have precipitated out of a magma ocean that is thought to have existed at the base of the mantle millions of years ago.
Jackson and her colleagues, who reported on their work in a recent paper in the Journal of Geophysical Research: Solid Earth, found evidence supporting the magnesiowüstite theory by studying the mineral's elastic (or seismic) anisotropy; elastic anisotropy is a variation in the speed at which seismic waves pass through a mineral depending on their direction of travel.
At the pressures and temperatures experienced at the earth's surface, magnesiowüstite exhibits little anisotropy. However, Jackson and her team found that the mineral becomes strongly anisotropic when subjected to pressures comparable to those found in the lower mantle.
Jackson and her colleagues discovered this by placing a single crystal of magnesiowüstite in a diamond anvil cell, which is essentially a tiny chamber located between two diamonds. When the rigid diamonds are compressed against one another, the pressure inside the chamber rises. Jackson and her colleagues then bombarded the sample with x-rays. The interaction of the x-rays with the sample acts as a proxy for how seismic waves will travel through the material. At a pressure of 40 gigapascals—equivalent to the pressure at the lower mantle—magnesiowüstite was significantly more anisotropic than seismic observations of ULVZs.
In order to create objects as large and strongly anisotropic as ULVZs, only a small amount of magnesiowüstite crystals need to be aligned in one specific direction, probably due to the application of pressure from a strong outside force. This could be explained by a subducting slab of the earth's crust pushing its way to the CMB, Jackson says. (Subduction occurs at certain boundaries between earth's tectonic plates, where one plate dives below another, triggering volcanism and earthquakes.)
The study is titled "Strongly Anisotropic Magnesiowüstite in Earth's Lower Mantle." Jackson collaborated with former Caltech postdoctoral researcher Gregory Finkelstein, now at the University of Hawai'i, who was the lead author of this study. This research was funded by the National Science Foundation and the W. M. Keck Institute for Space Studies.
Click here to read the full article written by Robert Perkins.
Mark Simons selected as an AGU Fellow for 2018The American Geophysical Union has chosen 62 new Fellows, including Mark Simons, John W. and Herberta M. Miles Professor of Geophysics and JPL Chief Scientist. Dr. Simon's recognition as a Union Fellow and election to the AGU College of Fellows is a prestigious and outstanding accomplishment. Mark has made fundamental contributions to our understanding of great earthquakes, volcanic systems and ice sheets through the application of space geodesy, especially radar interferometry. Simons is currently the co-lead of the NISAR satellite mission science definition team.
Established in 1962, the Fellows program recognizes AGU members who have made exceptional contributions to Earth and space sciences as valued by their peers and vetted by a committee of Fellows. The Fellows program serves to meet the needs of the science community and aims to motivate members to achieve excellence in research.
At this year’s Honors Tribute, to be held Wednesday, December 12, at the Fall Meeting 2018 in Washington, D. C., AGU will celebrate and honor the exceptional achievements, visionary leadership, talents, and dedication of the 62 new Fellows.
Congratulations Dr. Simons!
Click here for the complete list of the 2018 AGU Fellows.
Natalia Solomatova, former Seismo Lab student, is the recipients of one of the 2018 AGU Mineral and Rock Physics Graduate Research Awards for her PhD thesis work.
Established in 1990, the Mineral and Rock Physics Graduate Research Award is given annually to one or more promising young scientists (current Ph.D. students and individuals who have completed the degree requirements for a Ph.D. or highest equivalent terminal degree up to 12 months prior to the nomination deadline) in recognition of outstanding contributions achieved during their Ph.D. research.
The honorees and their achievements will be recognized at AGU’s Fall Meeting 2018 in Washington, D. C.
Congratulations Natalia!
Click here for the list of all 2018 section awardees and named lecturers.
Using an unprecedented number of satellite radar images, geophysicists at Caltech have tracked how the ground in Southern California rises and falls as groundwater is pumped in and out of aquifers beneath the surface.
The study, which was published online on April 30 by the journal Water Resources Research, uses publicly available radar data captured between 1992 and 2011 by European Space Agency satellites. The satellite data was compiled into 881 radar interferograms—images created by bouncing radar signals off of the earth's surface—to track nearly vertical ground motion down to the millimeter with a horizontal resolution of tens of meters, over an area that stretches from San Fernando, northwest of downtown Los Angeles, down to Irvine, in Orange County.
When all of the images are stitched together, they show the ground beneath Southern California rising and falling annually, like a giant breathing in and out. The results were checked against GPS measurements taken by the Orange County Water District (OCWD) and the Water Replenishment District of Southern California, which corroborated the findings. The periodic rising and falling of the ground tells the story of the management of Southern California's aquifers and how that management has changed over time, says Simons, the John W. and Herberta M. Miles Professor of Geophysics at Caltech and JPL chief scientist.
Riel, Simons, and co-authors relied upon data from ESA satellites. Meanwhile, JPL, NASA, and the Indian Space Research Organisation (ISRO) are planning to launch a new radar satellite called NISAR in early 2022 that will provide observations from two directions every 12 days—providing higher-quality, higher-resolution data than have previously been available." With that kind of data, we'll be able to paint an even clearer picture that could reveal even more about the ground beneath our feet," Simons says.
Click here to read the full article.
Congratulations to the 2018 GPS Division Graduates in the Seismo Lab Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates pictured (from left to right) Steve Perry, Chris Rollins, Daniel Bowden and Yingdi Luo.
Seismometer Readings Could Offer Debris Flow Early Warning Seismologists at Caltech noticed that the rumble and roar of the mudslide was detected by a seismometer about 1.5 kilometers away from the worst of the damage. Significantly, they found that the seismogram generated by the event reveals information about debris-flow speed, the width of the flow and the size of boulders it carried, and the location of the event— results suggesting that the current generation of seismometers in the field could be used to provide an early warning of an incoming debris flow to residents in mudslide-prone areas.
Professor Victor Tsai has long been interested in exploring what information can be gathered from seismometers beyond the usual earthquake signals they were designed to detect. "The motion of the ground can indicate a lot of things, from the detonation of a warhead to the motion of a glacier. The trick is determining what the signal means," he says. As such, he had already started working on a model that predicted what a mudslide should look like on a seismometer, based on existing models of sediment transported by water.
Collaborating with Professor Tsai, graduate student Voon Hui Lai gathered data from the three seismometers located within a few kilometers of the mudslide to search for the signal predicted by Tsai's model. Due to proximity and technical issues, two of the seismometers did not robustly record the slide. The third, however, did. "It wasn't immediately obvious, but after a while, we found it," Lai says.
Now that they know what to look for and have a model for what the seismogram is indicating, scientists can use this to develop an early warning system based on existing seismometers, Tsai says. "Debris flows move much slower than earthquakes, so we could potentially develop an early warning system that would offer important warnings for residents and first responders," he says.
The researchers plan to keep testing and fine-tuning the model using controlled experiments that yield more precise measurements.
Click here to read full article.
Olivia Pardo Receives a Department of Energy National Nuclear Security Administration Stewardship Science Graduate Fellowship
The Department of Energy National Nuclear Security Administration Stewardship Science Graduate Fellowship (DOE NNSA SSGF) provides excellent financial benefits and professional development opportunities to students pursuing a Ph.D. in fields of study that solve complex science and engineering problems critical to stewardship science.
The fellowship builds a community of talented and committed doctoral students, program alumni, DOE laboratory staff and university researchers who share a common goal to further their science while advancing national defense. The friendships and connections fellows make in the program continue to benefit them throughout their careers.
The Department of Energy’s National Nuclear Security Administration funds the DOE NNSA SSGF to train scientists vital to meeting U.S. workforce needs in advanced science and engineering.
Congratulations Olivia!
Click here for more information on the DOE NNSA SSGF.
Caltech has launched a new Southern California Seismic Network website that allows visitors to track earthquake activity with real-time seismic waveform displays.
“What we’ve tried to highlight was getting the information out as fast as possible so people can see real-time seismic activity near where they live,” says Jen Andrews, staff seismologist at Caltech. “If people get there fast enough, they can be watching an earthquake on the live seismograms as it happens.”
The site uses social media technology and is cloud hosted, so it can remain robust and usable even if millions of people try to access it after a major quake. Find out more at www.scsn.org.
Caltech students, postdoctoral scholars and faculty members joined together for the first Science for March open house. The event brought the local community and scientists together at Caltech to enjoy, share, and celebrate science. Seismo Lab students participated in this event and created an interactive earthquake booth which was enjoyed by all who attended.
Seismo Lab Graduate students included Benjamin Idini, Celeste Labedz, Voon Hui Lai, Valère Lambert, and Zhichao Shen.
Subduction zones are where one plate dives below another and are responsible for great earthquakes and volcanoes. But how a new subduction zone forms is an enduring mystery of plate tectonics. Now, a team of scientists lead by the Seismo Lab are carrying out a large seismic experiment where we know subduction is nucleating today. In the remote ocean south of New Zealand, the South Island Subduction Initiation Experiment, team is using ocean bottom seismometers and other seismic sensors to measure crustal properties, including imaging the nucleating megathrust between two tectonic plates. The team is using the state-of-the-art seismic research vessel, R/V Marcus Langseth, owned by the National Science Foundation. Seismo Lab Director Michael Gurnis, Chief Scientist of the expedition, is joined by Joann Stock, Professor of Geology and Geophysics, and Caltech geophysics students Erin Hightower, Ethan Williams, Erich Hertzig, and Benjamin Idini.
With Caltech graduate student Xiaolin Mao, Gurnis has been developing advanced computational models for how a new subduction zone forms. During initiation of subduction, new faults either form or existing faults reorient. Initially, the forces in a subduction zone are driven by plate motions, but eventually enough force builds up allowing the local slab to take over. This is a key transition from forced to self-sustaining subduction. Gurnis maintains that the area south of New Zealand, the Puysegur Trench, is making this transition. With scientists from the University of Texas Institute of Geophysics, the team aboard the R/V Langseth is making observations to test these geodynamic concepts in research funded by the National Science Foundation.
Please check out the news article and video from Otago News in Dunedin.
In the summer of 2017, Dr. Victor Tsai's graduate students Celeste Labedz and Daniel Bowden deployed 60 seismometers across the surface of Lemon Creek Glacier near Juneau, Alaska along with collaborators from the University of Idaho and the University of Alaska Southeast. These seismometers weren't looking for earthquakes, though; their goal was to sense the motion of water. If you stand near a rushing river, you can feel and hear the vibrations that moving water creates, and seismometers can sense it, too. There are channels of flowing liquid water below many glaciers, and they create seismic signals in the same way that rivers do. Because these channels are underneath so much ice, indirect observations like seismology are often the only way to gain information about them. The liquid water inside and underneath glaciers plays a big role in how the glaciers flow, fracture, and melt, so these seismological observations can provide important insight into glacier behavior.
Caltech Seismological Laboratory professor Joann Stock has been awarded a renewal of a KINGDOM Software Educational License plus two additional standalone licenses from IHS Global, Inc.
The additional three-year license plus two additional will allow continued interpretation of active source seismic data available from several locations (Antarctica, Mexico, Indian Ocean, Pacific Ocean, and Southern California).
The two extra licenses will be used on laptops that the students will use at sea during the cruise, and back on campus after the cruise. The course will be offered on board a seismic research vessel, the Marcus Langseth, in Feb-March 2018. The Caltech students will use the IHS Kingdom software as part of their MCS data analysis and interpretation during and after the cruise. See course description for
Ge 211, Applied Geophysics II. Participants will range from senior undergraduates to beginning graduate students.
IHS Global, Inc's KINGDOM® software integrates geoscience, geophysics and engineering into a single, easy-to-use software solution, enabling asset teams to make confident and faster decisions from exploration to completion. Our solutions are simplified, giving you access to advanced geoscience/scientific tools that are affordable, easy to learn and install and come with excellent support and training.
For more on Kingdom Software Educational Licenses click here.
As a gaggle of wide-eyed elementary school students crowd in for a view, first-year geophysics graduate student Celeste Labedz plunges her gloved hands into a basin overflowing with carbon dioxide fog.
Labedz's visit to Field Elementary School in Pasadena on May 18 was part of the Science Night program that brings more than 30 Caltech volunteers—undergraduate, graduate, and postdoctoral scholars in physics, chemistry, biology, geology, astronomy, and engineering—to conduct science demonstrations for students at 11 schools across Pasadena and the San Gabriel Valley.
Started in 2013, the program originally targeted three area schools, but grew rapidly as parents and teachers spread the word about the events, and more schools invited Caltech to partner with them, says Mitch Aiken, associate director for educational outreach in Caltech's Center for Teaching, Learning, and Outreach.
Aiken says the program helps expand Catech's community involvement and provides benefits not only to local schools and their students, but also to the Institute and its students.
Click to read article Science Night.
A team of engineers and scientists from Caltech and École normale supérieure (ENS) in Paris have discovered that fast ruptures propagating up toward the earth's surface along a thrust fault can cause one side of a fault to twist away from the other, opening up a gap of up to a few meters that then snaps shut.
Thrust fault earthquakes generally occur when two slabs of rock press against one another, and pressure overcomes the friction holding them in place. It has long been assumed that, at shallow depths, the plates would just slide against one another for a short distance, without opening.
However, researchers investigating the Tohoku earthquake found that not only did the fault slip at shallow depths, it did so by up to 50 meters in some places. That huge motion, which occurred just offshore, triggered a tsunami that caused damage to facilities along the coast of Japan, including at the Fukushima Daiichi Nuclear Power Plant.
In the Nature paper, the team hypothesizes that the Tohoku earthquake rupture propagated up the fault and—once it neared the surface—caused one slab of rock to twist away from another, opening a gap and momentarily removing any friction between the two walls. This allowed the fault to slip 50 meters.
That opening of the fault was supposed to be impossible.
Before an earthquake, static friction helps hold the two sides of a fault immobile and pressed against each other. During the passage of an earthquake rupture, that friction becomes dynamic as the two sides of the fault grind past one another. Dynamic friction evolves throughout an earthquake, affecting how much and how fast the ground will shake and thus, most importantly, the destructiveness of the earthquake.
Previously, it commonly had been believed that the evolution of dynamic friction was mainly governed by how far the fault slipped at each point as a rupture went by—that is, by the relative distance one side of a fault slides past the other during dynamic sliding. Analyzing earthquakes that were simulated in a lab, the team instead found that sliding history is important but the key long-term factor is actually the slip velocity—not just how far the fault slips, but how fast.
Mark Simons is part of a movement to add precise and panoramic perspectives to previously limited geographic observations.
The 2011 Japanese earthquake was a defining moment for Mark Simons. The devastating 9.0-magnitude quake and its subsequent tsunami, which took nearly 16,000 lives, spurred efforts around the globe that will shape how nations predict and prepare for future natural disasters and motivated new approaches to basic earthquake science that are applicable to seismic events large and small.
Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates pictured (from left to right) Bryan Riel and Semechah Lui.
The NSF Graduate Research Fellowship Program (GRFP) helps ensure the vitality of the human resource base of science and engineering in the United States and reinforces its diversity. The program recognizes and supports outstanding graduate students in NSF-supported science, technology, engineering, and mathematics disciplines who are pursuing research-based master's and doctoral degrees at accredited United States institutions.
As the oldest graduate fellowship of its kind, the GRFP has a long history of selecting recipients who achieve high levels of success in their future academic and professional careers. The reputation of the GRFP follows recipients and often helps them become life-long leaders that contribute significantly to both scientific innovation and teaching.
Congratulations Celeste!
Dr. Simons is a Professor of Geophysics in the Seismological Laboratory within the Division of Geological and Planetary Sciences at Caltech.He received his B.S. in Geophysics and Space Physics from UCLA in 1989 and his Ph.D. in Geophysics from MIT in 1996. He joined Caltech as a Postdoctoral Scholar in 1995 and has been a full Professor there since 2007.
Mark's relationship with JPL started in 1990 as a graduate student working with gravity and SAR imagery data of Venus from the Magellan mission. Since then, his research has focused on advancing the ability of space geodesy – using technologies such as interferometric synthetic aperture radar (InSAR) and global navigation satellite system (GNSS) – to measure deformation of Earth's surface.
In collaboration with JPL, Mark currently serves as Caltech's Co-Principal Scientist for the Advanced Rapid Imaging and Analysis (ARIA) Project and is the solid earth science co-lead for the NISAR science definition team.
