15. Complete Solution of the Earthquake Rupture and Ground Motion Problem
Exciting advances have recently been made in the areas of dynamic fault rupture modeling, scattering in 3-D velocity media, and nonlinear soil effects. These advances have brought earthquake ground motion prediction to a critical stage of development, poised for a major, culminating breakthrough. Complete time histories of ground motion are critical for performance-based engineering analysis which is a grand challenge for the earthquake engineering community. Dynamic rupture models, which incorporate a physical relationship between the three important faulting parameters of stress drop, rupture velocity, and rise time, have become accessible. However, modeling of ground motion records has shown that the frequently applied slip-weakening friction law in dynamic analysis does not satisfy some critical elements of observed faulting behavior in terms of short rise times. Nevertheless, this work has also shown that we are tantalizingly close to a dynamic theory that is physically justified and predicts observed ground motions. Parallel to the advances in dynamic analysis, significant strides have been made in wave propagation through realistic 3-D velocity structures that include scattering effects and complicated geometries such as sedimentary basins. In addition, we are now able to accurately model the effects of shallow soils that behave nonlinearly during strong shaking. This parallel work is of great importance because ground motion recorded at the surface of the Earth is the convolution of source, path, and site effects. It is not possible to fully resolve one effect without similar clarity of the other effects. We are now in a position to pull together these source, path, and site effects into a unified theory of the earthquake source and resulting ground motion. This research opportunity calls for an individual with expertise in dynamic earthquake source modeling. The incumbent will develop alternative dynamic models that address the rise time problem of the slip-weakening friction law. He/she will incorporate these dynamic models into realistic 3-D velocity models that include the effects of scattering and sedimentary basins. The successful candidate will work with senior USGS scientists who are experts in wave propagation through realistic Earth structures, in nonlinear soil effects, and in the evaluation of dynamic models and their ability to explain earthquake ground motions.
Proposed Duty Station: Golden, CO
Areas of Ph.D.: Seismology, geophysics, or related field
Qualifications: Applicants must meet one of the following qualifications: Research Geophysicist
(This type of research is performed by those who have backgrounds for the
occupations stated above. However, other titles may be applicable depending
on the applicant's background, education, and research proposal. The final
classification of the position will be made by the Personnel specialist.)
Research Advisor(s): Steve Hartzell (303) 273-8572, shartzell@usgs.gov; Arthur D. Frankel (303) 273-8556, afrankel@usgs.gov
Personnel Office contact: Kathleen Scheich, (303) 236-9581, kscheich@usgs.gov
U.S. Department of the Interior, U.S. Geological Survey
URL: http://geology.usgs.gov/postdoc/2006/opps/opp15.html
Direct inquiries to Rama K. Kotra at rkotra@usgs.gov
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Last modified: 12:06:32 Tue 24 Aug 2004
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