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Crustal Deformation and Fault Mechanics

 
    Crustal Deformation and Fault Mechanics

 

 

 

Information for prospective students

I am always looking for outstanding students to work with. This page is designed to give an idea of our current activities, my philosophy of working with students, and some details on funding and applications.

My students are all exposed to the full spectrum of activities in Crustal Deformation and Fault Mechanics, ranging from data gathering, data analysis and inversion, and mechanical modeling. In the data collection realm we focus principally on measuring crustal deformation with high precision GPS.  Averaging over 24 hour periods we are able to obtain a precision of roughly 2 mm in the horizontal components and 6 mm or so in the vertical. We collaboratively operate a permanent GPS network on the active volcanoes Kilauea and Mauna Loa on the Big Island of Hawaii with the U.S. Geological Survey and have had field projects on the San Andreas Fault system in California, Long Valley Caldera, and elsewhere. We also look at GPS signals on much shorter time scales, and have developed innovative processing methods that directly invert GPS observables for time-varying fault slip.   We also analyze Interferometric SAR data (in collaboration with Prof. Howard Zebker and his students), tilt and borehole strain, and other data that help to reveal earthquake and volcanic processes.  

We do go well beyond reducing the data to determine displacements and velocity vectors. These data are not an end in themselves, but a resource to learn about physical processes in the earth. We use inverse methods to learn about the geometry of active faults and magma chambers within the earth, the slip distribution on faults during earthquakes, as well as the distribution of aseismic slip during the interseismic period between large earthquakes. We have developed many new methods for interpreting and inverting data, including innovative methods for determining the spatial and temporal variations of slip-rate on faults. These methods have allowed us to image aseismic slip following large earthquakes and so-called “silent earthquakes” recently discovered in Japan, Cascadia, and by us on the Big Island of Hawaii.

Our research does not stop with the inversion results. These may tell us what faults, dikes, or magma chambers are consistent with the data. They do not tell us why a particular fault slips, or if its slips whether it will creep slowly or rapidly in a damaging earthquake.  Typical inversion also don’t address whether a particular dike will stop in the earth as an intrusion or breach the surface leading to an eruption. To better understand these processes we develop physical models based in the concepts of continuum mechanics. In order to understand how plate motions load active faults we develop models of plate boundary processes, including viscoelastic deformation of the lower crust and or upper mantle. To better understand how earthquakes nucleate we investigate the stability of frictional sliding with rate and state friction including the effects of dilatancy, pore-fluid flow, and shear heating. This has involve numerical solution of coupled non-linear partial differential equations using a combination of boundary integral and finite difference methods. We have also studied how human activity in petroleum and geothermal fields have triggered earthquakes.

While students have tended to focus mainly on the data analysis and inversion side, or conversely on the mechanical modeling side, my goal is that by the time they graduate they are well versed in all aspects of the field. I believe that it is this balance that has made my former students so successful in finding jobs in the field.

Ideally, I would like to maintain a balance between students working on earthquake and volcanic processes.

In working with students, I try to help them find a project that meets three objectives (in order of importance): (1) The student is really excited about the work. This is key. Students work hard for several years—their research should be something they are fired up about; (2) I feel that the problem being addressed is significant, fits the students background, and is one I can competently supervise. In some cases we work closely with other faculty or with scientists at the nearby U.S. Geological survey; (3) There is funding or a high likelihood of obtaining funding.  We are fortunate at Stanford to have considerable Fellowship funding.   In addition, I have historically had robust funding from the National Science Foundation, the U.S. Geological Survey Earthquake Program, the Southern California Earthquake Center, and NASA. I have never had to turn away a student for lack of funding.

If you would like more information on the group please contact me. It's also a good idea to contact the students in the group. They'll be able to provide candid answers to all your questions about what it's like to be a grad student in this department. They'll also be able to give you an idea of what to expect in terms of academics and research. If possible, come for a visit.
    
Check out our department's Admissions web page. It provides information on procedures to apply to the Geophysics Department.

A special note on Geophysics at Stanford: Stanford is unusual in that we have a School of Earth Sciences, with Geophysics and Geological and Environmental Sciences (GES) as separate departments. Some students are unsure which department they fit best with. While most of my students have been in Geophysics, I have worked successfully with students in GES in the past. If your interest is clearly in crustal deformation or the physics of faulting, I would recommend applying to Geophysics. If your interests are broader but you would like to get involved in our research, don't worry too much about the departmental boundaries—they are porous. As long as you are willing to gain the necessary background there is no reason we cannot work together. If you are unsure, send me an email.

Prof. Paul Segall

  Last modifiedWednesday, 14-Jan-2015 16:43:15 PST
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