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David G. Harkrider, professor of geophysics, emeritus, at Caltech and an expert in seismological wave propagation, has passed away on Tuesday, February 16, 2016. He was 84.
Born on September 25, 1931 in Houston Texas. Harkrider received his bachelor's and master's degrees from Rice University in 1953 and 1957, respectively. He earned a doctorate in geophysics from Caltech in 1963 and remained as a research fellow until 1965, when he joined the Department of Geology at Brown University as an assistant professor. Harkrider returned to Caltech as an associate professor in 1970, becoming a professor in 1979 and a professor emeritus in 1995. From 1977-1979 he was the associate director of Caltech's Seismological Laboratory.
The slow slip aseismic, in the deep part of the tectonic faults is the main mechanism of accumulation of efforts in the engaged area. The deformation areas outside seismic coupling also causes intermittent seismic processes, for example swarms of tremors or earthquakes. Seismic monitoring of these processes allows to study the slow deformation. The phenomenon of episodic slow earthquakes accompanied by tremors is indicative of the heterogeneity of the physical properties of faults. During large subduction earthquakes, such as Tohoku, Japan, 2011 the coexistence of fast and slow processes are manifested by the spatial separation between the sliding areas of high and low frequency, revealed by studies of broadband source. The separation is also evident in the 2015 earthquake in Nepal, at high frequencies located in the deep part of the rupture zone, coinciding with the belt of seismicity background, mechanics and numerical and experimental models of seismic cycle allow us to understand these processes of rupture and its impact on the distribution of the intensity of the damage caused by the quake. In urban areas, new monitoring systems allow us to detect micro-seismicity more fully. This has revealed the existence of very deep earthquakes in the roots of an active fault in Los Angele, in the upper mantle. The unusual features of this deep seismicity can be interpreted in the context of models of rupture in heterogeneous fault areas.
Since the late 1970's, Caltech seismologist Tom Heaton, professor of engineering seismology, has been working to develop earthquake early-warning (EEW) systems- networks of ground-based sensors that can send data to users when the earth begins to tremble nearby, giving them seconds to potentially minutes to prepare before shaking reaches them. EEW systems have been implemented in countries like Japan, Mexico, and Turkey. However, the United States has been slow to regard EEW systems as a priority for the West Coast.
But on February 2, 2016, the White House held the earthquake Resilience Summit, signaling a new focus on earthquake safety and EEW systems. There, stakeholders-including Caltech's Heaton and Egill Hauksson, research professor in geophysics; and USGS seismologist Lucy Jones, a visiting associate in geophysics at Caletch and seismic risk advisor to the mayor of Los Angeles-discussed the need for earthquake early earning and explored steps that can be taken to make such systems a reality.
At the summit, the Gordon and Betty Moore Foundation announced $3.6 million in grants to advance a West Coast EEW system called ShakeAlert, which received an initial $6 million in funding from the foundation in 2011. The grants will go to researchers working on the system at Caltech, the USGS, UC Berkeley, and the University of Washington.
When a series of earthquakes struck the Baldwin Hills area of Los Angeles County, California in early 2015, local residents were concerned that the use of hydraulic fracturing and other drilling activities in the nearby oil field might have played a role in triggering the quakes.
In response, the community worked with the Union of Concerned Scientists (UCS) and the Thriving Earth Exchange to identify an academic expert in earthquakes and their relationship to oil drilling. Jean-Paul (Pablo) Ampuero, Ph.D., an assistant professor of seismology at the California Institute of Technology who studies the physics of earthquakes, turned out to be a perfect scientific partner for the community. Dr. Ampuero, who is originally from Peru, was particularly interested in helping the community because of its large Hispanic population.
The resulting partnership not only helped to inform residents and calm their fears, but also formed a lasting relationship that continues to deliver the latest seismology research to the community.
Deep inside the earth, seismic observations reveal that three distinct structures make up the boundary between the earth's metallic core and overlying silicate mantle at a depth of about 2,900 kilometers- an area whose composition is key to understanding the evolution and dynamics of our planet. These structures include remnants of subducted plates that originated near the earth's surface, ultra-low velocity zones believed to be enriched in iron, and large dense provinces of unknown composition and mineralogy. A team led by Caltech's Jennifer Jackson, professor of mineral physics, has new evidence for origin of these features that occur at the core-mantle boundary.
Seismo Lab Director Michael Gurnis with a team of scientists from the University of Texas, IBM Research and New York University were awarded the prestigious Gordon Bell Prize at the annual Supercomputing Conference. The team developed innovative algorithms for a mathematical approach called an "implicit solver" to realistically simulate mantle convections and plate tectonics at ultra-high resolution and accuracy. The new software reached an unprecedented 97 percent parallel efficiency in scaling the solver to 1.6 million cores, a new world record. [PR Newswire]
In the event of a major earthquake in Los Angeles, first responders ideally would immediately have a map of the most intense shaking around the city-allowing them to send help to the hardest-hit areas first.
A new collaboration between Caltech researchers and schools of the Los Angeles Unified School District (LAUSD) provides a crucial step in the creation of such damage maps by vastly broadening the scope of a dense network of seismic sensors in the Los Angeles basin. [Caltech Article]
By many who owe him much
The following reminiscences, scientific and otherwise, were contributed by Don Anderson's scientific colleagues. Incomplete though they are, they give a flavor of the extraordinary range of Don's activities, his influence on Earth science, and the phenomenon that was the Caltech Seismological Laboratory in his time.
Click here to read full article.
Located primarily in the Seismological Laboratory, the Geophysics Option in the Division of Geological and Planetary Sciences provides unique opportunities for graduate students to excel in academics and engage in cutting-edge research. The Seismo Lab welcomes Jorge Castellenos, Jack Muir, and Minyan Zhong.
Jorge received his B.S. degree in Geophysical Engineering at the Autonomous University of Nuevo Leon. In 2015, he received a M.S. in Earth Sciences at the National Autonomous University of Mexico, where he worked with large seismic array datasets to characterize subduction zone dynamics underneath Mexico. His main research interests are geodesy, seismic wave propagation and the use of inverse theory to determine Earth structure. When asked why he chose Caltech, Jose says, “Caltech provides me the opportunity to explore freely the different branches of Earth Science while working with the World leading researchers in these fields.”
Jack received a Bachelor of Philosophy with honors in physics from the Australian National University in 2014. He has done internships in condensed matter physics, astrophysics, and geophysics. Jack has worked on projects involving Bayesian inference applications to the differential rotation of Earth’s inner core and Joint inversion of lowermost mantle P-wave velocity and core-mantle boundary topography. His research interests include inverse problem methods, bayesian statistics, ambient noise correlations and deep mantle structure. For Jack, “Caltech is an exciting place to work due to the large and diverse faculty and student body, which provides a wealth of experience on which to draw.”
Minyan received his B.S. from Peking University (Beijing, China) in 2015, double-majoring in Geophysics and Software Engineering. During his undergraduate studies, he worked on problems related to surface wave tomography, in order to retrieve surface-wave phase velocity across seismic arrays. He is interested in ambient seismic noise, development of Geophysical methods, and EQ physics related to super shear rupture. When asked why he chose Caltech, Minyan says, “There are many world-class faculty here, working in different subfields of geophysics, and the atmosphere of collaboration here is really great.”
One of the biggest unknowns in understanding the effects of climate change today is the melting rate of glacial ice in Antarctica. Scientists agree rising atmospheric and ocean temperatures could destabilize these ice sheets, but there is uncertainty about how fast they will lose ice.
The West Antarctic Ice Sheet is of particular concern to scientists because it contains enough ice to raise global sea level by up to 16 feet, and its physical configuration makes it susceptible to melting by warm ocean water. Recent studies have suggested that the collapse of certain parts of the ice sheet is inevitable. But will that process take several decades or centuries? [Caltech Article]
Michael is a senior at Caltech, majoring in Mechanical Engineering. This fall he entered the Master's program in Geophysics, which is part of the B.S./M.S. program for undergraduate students at Caltech. Michael is from Richmond, Virginia and after attending Caltech's pre-frosh weekend, he knew Caltech was the best fit for him. This past summer, Michael worked on acoustic emission experiments at Schlumberger in Salt Lake City. When he is not working on magnetostratigraphy or tutoring at the Hixen Writing Center, he is working on an electric-powered go-kart for the Society of Automotive Engineers "Formula SAE" competition.
Seismo Lab Postdoctoral Scholar, Hsin-Hua Huang, is interested in exploring various tectonic problems seismologically and gaining better understanding of Earth structure, including a wide spectrum of topics such as regional structural kinematics, unusual earthquake sequences, mountain building process, 3-D slab interaction, and crustal magmatism system. One of his recent focuses is on improving seismic imaging from the shallow crust to the upper mantle with multi-dataset joint inversion and waveform methods. In the meantime, he is also working on seismic interferometry to extracting new body-wave data set from earthquake coda and probing the deep Earth. One of his works that unveils the lower crustal magma reservoir beneath the Yellowstone has recently been published on journal Science.
The Earth is a living planet, as revealed by tectonic processes spanning various time and spatial scales, including earthquake, volcano eruptions, mountain building, basin formation, etc. All these tectonic processes are dominated by the solidus buoyancy flow inside the Earth's mantle - mantle convection.
Southeast Asia is a unique place to investigate the effects of mantle convection on surface tectonics. This intriguing place has the most prominent low dynamic topography on Earth at present, as indicated by numerical models and observations.
Sundaland, the continental core of Southeast Asia, underwent intense deformation in the past, as revealed by the low seismic velocity in the lithosphere and upper mantle, widespread rifting basins and high heat flux. However, Sundaland is tectonically quiet at present and manifests as the low seismicity and strain rate. We investigate global mantle viscosity and temperature structures with the constraints of geoid, free air gravity, gravity gradients and residual topography.
With the knowledge of mantle temperature and viscosity structures, we focus on the dynamic evolution of Southeast Asia, with dynamic models considering both lithospheric scale deformation and mantle convection. We demonstrate that a large mass of dense, cold slab material lay horizontally within the transition zone beneath southern Sundaland before the Miocene, due to the impedance of the 660 phase boundary. During the early Miocene the stagnant slab became unstable and penetrated into the lower mantle, forming a slab avalanche event. This slab avalanche event induced significant change in large scale topography, stress field and basin regimes and sedimentary environments in southern Sundaland.
We suggest that the slab avalanche might have occurred beneath other subduction zones and generated strong changes on surface tectonics.
The Mineral and Rock Physics focus group of the American Geophysical Union has awarded Dongzhou Zhang the 2015 Graduate Research Award, in recognition of his Ph.D. thesis work on the development and application of new techniques to constrain melting points of iron-alloys under extreme conditions.
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.
Click here for a list of present and past recipients.
At the Annual Meeting of COMPRES last week in Colorado Springs, a contest was conducted to select the best poster presenter, with the winners to receive one of the 150 Euro book vouchers from Springer-Verlag. Natalia won for her presentation of "Spin crossover and equation of state of (Mg.Fe)O". All four winners were graduate students currently at member institutions of COMPRES.
The winners are:
Alisha Clark, University of California Davis
Rebecca Fischer, University of Chicago
Dylan Rittman, Stanford University
Natalia Solomatova, Caltech
Click here for information on COMPRES.
Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduate Dongzhou Zhang.
The American Geosciences Institute has named Hiroo Kanamori, John E. and Hazel S. Smits Professor of Geophysics, Emeritus, as the recipient of the Marcus Milling Legendary Geoscientist Medal for 2015.
The Marcus Milling Legendary Geoscientist Medal is given to a recipient with consistent contributions of high-quality scientific achievements and service to the Earth Sciences having lasting, historic value; who has been recognized for accomplishments in field(s) of expertise by professional societies, universities, or other organizations; and is a senior scientist nearing completion or has completed full-time regular employment. Prior to 2007 it had been called the AGI Legendary Geoscientist Award.
Congratulations Dr. Kanamori!
Click here for the list of previous recipients
Caltech Seismological Laboratory professor Joann Stock has been awarded a renewal of a KINGDOM Software Educational License from IHS Global, Inc.The amount of this 3 year grant is valued at $3,798,900.
The additional three-year license will allow continued interpretation of active source seismic data available from several locations (Antarctica, Mexico, Indian Ocean, Pacific Ocean, and Southern California).
In addition, a student training class in marine geophysics on board ship in spring 2016 is in the initial planning stages. The cruise will collect multichannel seismic data in the Eastern Pacific Ocean. (See course description for Ge211, Applied Geophysics 11).
IHS Global, Inc's KINGDOM® software is an intuitive, cost-effective geoscience software solution. Kingdom combines simplicity and sophisticated science to provide basin-wide capabilities, advanced field evaluation, seismic and geological interpretation to well site identification and planning.
For more on Kingdom Software Educational Licenses click here.