Spotlight

Seismo Lab Students Present at 2012 AGU Fall Meeting

December 3-7, Seismo Lab students presented their research at the American Geophysical Union (AGU) annual Fall meeting. They reported their findings on a range of topics, reflecting the diversity of studies undertaken in the Seismo Lab and the collaborative approach to addressing research questions.

Asaf Inbal

I use a wide range of seismic and geodetic observations to investigate the March 11, 2011, M9.0 Tohoku-Oki earthquake. I am mainly focusing on details of high-frequency energy radiation during the earthquake rupture and the spatio-temporal distribution of early post-seismic slip and aftershocks.

Learn more about Asaf's research here

Yihe Huang

Yihe Huang presented an observation- based dynamic model of the 2011 Mw9.0 Tohoku-Oki Earthquake. The model explains the physics behind the anomalous slip in the shallower region and high-frequency radiation in the deeper region. This research sheds some light on the mechanism of other megathrust earthquakes.

Learn more about Yihe's research here

Hilary Martens

Hilary R. Martens presented observations and modeled predictions of Earth's response to ocean tidal loading in South America. The material properties of the underlying crust and mantle determine the spatial and temporal characteristics of the response for a given load; hence, matching predictions to observations can provide insight into the elastic structure of the Amazonian craton.

Learn more about Hilary's research here

The AGU annual Fall meeting, held in San Francisco, is the largest gathering of Earth scientists in the World and the premier conference for geophysics. Each year Seismo Lab students, post-docs and faculty showcase their research through invited talks, oral presentations, and poster sessions.

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Egill Hauksson, Senior Research Associate in Geophysics

Egill Hauksson and his group are analyzing the waveform relocated (1981 to 2011) catalog of more than 500,000 earthquakes recorded in southern California, and assign geophysical parameters such as heat flow and GPS-measured shear strain rate to each epicenter. They synthesize this new data set to show that the seismicity occurs preferentially in crust that is neither too cold nor too hot, as it accommodates plate-boundary loading at shear strain rates that are also neither too slow nor too fast. They have also measured the distance between each of the 500,000 hypocenters and the closest principal slip surface of a late Quaternary fault (PSZ) as mapped in the SCEC Community Fault Model (CFM). These new earthquake parameters allows them to investigate how different properties of the seismicity change with distance from the nearest PSZ.

Dr. Yang (Caltech PostDoc) and Dr. Hauksson are also using a data set of more than 170,000 earthquake focal mechanisms to determine the patterns of crustal stresses across southern California. These stresses reflect how southern California is deforming in response to the Pacific North-America plate motion. A detailed image of the style of faulting as well as of the orientation of stresses along the major late Quaternary faults is emerging. They are comparing these results with other data sets such as strain rate maps derived from GPS observations across southern California.

Learn more about Egill Hauksson’s research here

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Drop, Cover and Hold On!

Caltech to participate in the Great California Shakeout

Get ready to drop, cover and hold on! On Thursday, October 18, Caltech will once again participate in the Great California Shakeout, the annual statewide earthquake-preparedness drill. Caltech studnts, faculty, staff, and visitors are encouraged to join the more than 8 million Californians who will have the opportunity to practice how to protect themselves during an earthquake.

Congratulations to 2012 GPS Division Graduates

Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates (from left to right) Ting Chen, Daniel Bower, Laura Alisic and Caitlin Murphy. They are pictured here with Michael Gurnis, Director of the Seismological Laboratory.

Michael Gurnis, John E. and Hazel S. Smits Professor of Geophysics and Director of the Seismological Laboratory

Mike Gurnis’s research is aimed at a better understanding of the dynamics of the solid earth, especially plate tectonics and mantle convection. With his students and post-docs, Mike primarily uses computational methods to understand the physics of processes in the lithosphere and mantle as well as a vehicle to interpret a wide variety of geological and geophysical observations. His group has been involved in the development of new computational methods that have pushed the envelope of realism and resolution, including global simulations of plate tectonics. The team makes use of not only our own in-house GPS-supercomputer, but also the facilities of National supercomputer centers. Over the last several years, Mike has pushed forward on three parallel research directions that use ultra-high resolution dynamic models of the present day earth, evolutionary models over the last several hundred million years of earth history, and studies of the earth’s deep interior. Much of the work is carried out in collaboration with other specialists including other faculty in the Seismo Lab and Tectonics Observatory and collaborators around the world. Learn more about Mike Gurnis’s research here

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M5.8 Earthquake Hits Virginia on August 23, 2011 at 1:51 p.m. EDT

Please click here for more information

GPS Division-Seismo Lab Welcomes Victor Tsai, Assistant Professor of Geophysics

Victor joined the GPS Division-Seismo Lab July 1, 2011. He is no stranger to Caltech, as he completed his undergraduate work here. He did his graduate work at Harvard University and then held a postdoctoral researcher position there. After Harvard, he worked for the U. S. Geological Survey in Colorado as a postdoctoral fellow.
Victor's research lies mainly at the intersection of seismology, geomechanics and other disciplines like glaciology, oceanography, and mathematical geophysics. One of his primary goals is to understand sources of ambient seismic noise and how these sources can be used to provide constraints on Earth structure (e.g. through ambient noise tomography) and other physical processes (e.g. sea ice interactions with ocean waves). He is also working to understand the short-timescale variability of glaciers and, in particular, is modeling rapid drainage of water in glaciers and the implications of this drainage. In addition, Victor is interested in improving seismic imaging techniques and geophysical time series analysis. Learn more

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Congratulations to 2011 GPS Division Graduates

Congratulations to the Geological & Planetary Sciences Division graduates! In particular, we would like to recognize the Seismological Laboratory's Geophysics doctoral graduates YoungHee Kim and Michelle Selvans. Their theses were entitled "Properties of the Subduction System in Mexico" and "Geophysical Investigations of Near-Surface Structure on the Earth and Mars" respectively.

Caltech Researchers Release First Large Observational Study of 2011 9.0 Tohoku-Oki Earthquake

PASADENA, Calif.—When the magnitude 9.0 Tohoku-Oki earthquake and resulting tsunami struck off the northeast coast of Japan on March 11, they caused widespread destruction and death. Using observations from a dense regional geodetic network (allowing measurements of earth movement to be gathered from GPS satellite data), globally distributed broadband seismographic networks, and open-ocean tsunami data, researchers have begun to construct numerous models that describe how the earth moved that day. For the full story, click here.

Click here to read article in Science Magazine: Science Express.

Jean-Philippe Avouac, Professor of Geology and Tectonics Observatory Director

Jean-Philippe's research aims mainly at understanding better the dynamics of the earth crust and lithosphere. He therefore studies earthquakes as well as continental deformation. He has a long lasting interest in orogenic contexts (the Himalaya and Tibet in particular). More recently, he has started working on subduction zones in the Sumatra and South America context. With the help of various colleagues and collaborators, the students and postdoc working with him use seismology, geodesy, and satellite imagery to quantify deformation over the short time scale of the seismic rupture or of pre-seismic strain buildup and postseismic relaxation. The kinematic models derived from those studies are then used to develop dynamic models and theories of faults behavior and of lithospheric deformation. To quantify tectonic processes over the longer term time scale of thousands to millions of years, they use geomorphology, structural geology and thermobarometry in conjunction with geochronology and thermochronology. Learn more about Jean-Philippe’s research at www.gps.caltech.edu/~avouac.

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Thomas Heaton, Professor of Geophysics and Engineering

Tom Heaton is the Director of Caltech’s Earthquake Engineering Research Laboratory. Much of his research centers on understanding the nature of great earthquakes and their impact on the built environment. He is helping to develop a new earthquake alerting network in California that promises to provide seconds of warning that earthquake shaking is about to strike. Tom has also had a long standing interest in understanding the physics of the earthquake rupture process. In the past decade, this has centered on understanding the implications of transitions between high static fault friction and low dynamic friction. Friction laws of this type lead to dynamic chaos in the rupture process. Learn more about Tom’s research at http://heaton.caltech.edu.

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Community Seismic Network

We are developing a new earthquake monitoring (seismic network) system, Community Seismic Network (CSN) based on a dense array of low-cost sensors. The goal of the system is to produce block-by-block estimates of strong ground shaking. The information from these sensors will be sent to central computers that will process the data and produce localized estimates of ground shaking on a block-by-block basis - essentially, motions of the evolving seismic wave field during local earthquakes. This information will guide emergency responders and promises to lead to a new level of understanding of the physics of earthquakes and their impact on Southern California. The development of the new network is partially supported by the National Science Foundation (NSF). Read more

Learn more about Prof. Robert Clayton

Jean-Paul Ampuero, Assistant Professor of Seismology

Jean-Paul Ampuero's research is primarily aimed at understanding the physics of earthquakes through the development of theoretical models, computational techniques and novel ways to record and image earthquake sources. One of my current research topics is the recently discovered phenomena of slow slip and non-volcanic tremor. I have developed a unifying model to explain the diversity of migration patterns of tectonic tremor, their scaling properties and their relation to slow slip transients. I am also involved in the search for spontaneous tectonic tremors in southern California, with a current focus on the San Jacinto fault. My team is involved in seismological experiments in South America. We were among the first to deploy broad band seismometers in Chile following the 2010 M8.8 Maule earthquake. Its largest aftershock, the 2011 M7.1 Araucania earthquake, was caught by our network clustered around the Arauco peninsula. Our next adventure will take us to southern Peru in search of tectonic tremors. Learn more

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Seismo Lab Students Present at the AGU Fall 2010 Meeting

December 13-17, Seismo Lab students will present their research at the American Geophysical Union (AGU) annual Fall 2010 meeting. They will report their findings on a range of topics, reflecting the diversity of studies undertaken in the Seismo Lab and the collaborative approach to addressing research questions.

Dan J. Bower will present a new geodynamic and mineral physics model for an ultra-low velocity zone (ULVZ). ULVZs are patches of much reduced seismic velocities at the core-mantle boundary that were first discovered at Caltech in the 1990s by students working with Prof. Don Helmberger.

The AGU annual Fall meeting, held in San Francisco, is the largest gathering of Earth scientists in the World and the premier conference for geophysics. Each year Seismo Lab students, post-docs and faculty showcase their research through invited talks, oral presentations, and poster sessions.

Learn more about Dan J. Bower's research
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Don Helmberger, Professor of Geophysics

Don Helmberger's research concentrates on modeling seismograms using both numerical and analytical methods. Because seismograms contain information about earthquake sources and earth structure, they both must be addressed in modeling. Thus, we study source complexity ranging from .2s to 50s involving events ranging from Mw= 2 to 9. Using such sources, we can examine the detailed structures in the earth from shallow features beneath Yellowstone to Superplumes near the Core-Mantle Boundary. Learn more

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Jennifer Jackson, Assistant Professor of Mineral Physics

Jennifer's research focuses on combining experimental results with geophysical methods to better understand planetary interiors.  By combining a suite of spectroscopic methods, primarily at advanced radiation sources, she determines the elastic, vibrational, and chemical properties of candidate planetary materials under extreme conditions of pressure and temperature.  Through collaborations with Seismo Lab colleagues, she integrates the most recent mineral physics results with seismic observations and geodynamic modeling to gain a multi-dimensional understanding of the deepest parts of Earth's interior. Learn more

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Mark Simons, Professor of Geophysics

Mark’s research focuses on combining geodetic observations with geodynamic models to understand the mechanics of the lithosphere and upper mantle. Currently, he primarily focuses on seismic, aseismic, and volcanic processes as constrained by interferometric radar and GPS data. In a related effort, he is working on ways to incorporate modern geodetic data into rapid earthquake models for assessment and response applications. Mark also studies large scale tectonic processes on the terrestrial planets using gravity and topography data. Recent projects focus on the use of Bayesian approaches to estimating kinematic fault models, internally consistent frictional models of fault slip in subduction zones, automatic aseismic transient detection systems for GPS and InSAR time series using multi-scale approaches, and models for recent large earthquakes in Haiti, Chile, and Baja California. Learn more

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The Salton Seismic Imaging Project

The Salton Seismic Imaging Project is a large-scale active seismic survey that will take place in Feb. 2011 to study earthquake hazards and rifting processes in southeastern California (Imperial and Coachella Valleys) and northwestern Mexico (Mexicali Valley). These valleys are formed by right-lateral strike-slip faulting, extension, and magmatic intrusion between the Pacific plate (on the west) and the North America plate (on the east). Because the southern San Andreas fault ends in this region, its slip is transferred to a number of other active faults that bound the mountain ranges and valleys, and extend under water into the Gulf of California. The project will create images of subsurface geology to investigate the different plate tectonic processes and the earthquake hazards they cause. We will image the deep structures in the basins and the geometry and interconnectivity of the active faults. The images will determine the subsurface geometry of the southern San Andreas fault, and the thickness and physical properties of the basin sediments - all of which are critical in order to simulate the expected shaking from a major earthquake. The survey will involve about 3000 seismometers deployed for 3 weeks, and a set of sound waves generated from boreholes a few hundred feet below the surface. Learn more

Learn more about Prof. Joann Stock

Swami Krishnan, Assistant Professor Earthquake Engineering Researcher

Swaminathan Krishnan is an Assistant Professor of Civil Engineering and Geophysics at Caltech and a structural engineer specializing in earthquake engineering. Professor Krishnan leads the earthquake engineering simulation group (http://krishnan.caltech.edu/) which pursues fundamental research in earthquake engineering with applications to end-to-end simulation of earthquakes and structural response using high-performance computing. End-to-end simulations consist of holistically simulating the earthquake process, starting with fault rupture, generation and propagation of seismic waves to a site(s) of interest, and shaking of the top-soil layer, simulating the structural response including soil-structure interaction, and estimating the losses due to damage, and the opportunity cost due to interruption of structure usage. Learn more

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