SCEC Award Number 10001 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Application of physics-based rate and state friction to nonlinear strong ground motions and crustal faults
Investigator(s)
Name Organization
Norman Sleep Stanford University
Other Participants
SCEC Priorities A7, A8, B2 SCEC Groups FARM, GMP, CDM
Report Due Date 02/28/2011 Date Report Submitted N/A
Project Abstract
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Intellectual Merit We apply lab and thermodynamic based physics of brittle rocks to understand the behavior of crustal faults throughout the earthquake cycle and the shallow subsurface during strong shaking. We contributed to the modern theory of earthquake rupture by showing that the width of the principle slip zone in major faults self organizes so that the initial slip pause causes stresses that just trigger dynamic failure in the surrounding rock. We obtained limits for the strength of shallow rock during extreme shaking and how shallow brittle rock self organizes so that shaking leaves residual stresses on fractures that act as pre-stressed regions during the next shaking. This led to simple formulation for shallow nonlinear attenuation of strong seismic waves. We are currently investigating moderately shallow (10s of meters) seismically driven hill slope creep (sackungen) as a long term exceedance on strong ground motions and a calibration of nonlinear ground failure.
Broader Impacts Nonlinear ground behavior is societally relevant as most structures rest on the surface of the Earth. We seek to constrain this process by applying physics and by monitor the past rock failure. We thus obtain long term exceedance criteria for strong ground motions. As a byproduct of seeking examples of nonlinear ground failure, we have obtained an explanation of strong accelerations 0.8 g at Lucerne California (LUC) in the Landers earthquake in terms of shallow directional site resonances. This datum is in most peak ground acceleration versus distance compilations. It is useful for engineering to understand that it is a shallow high frequency process and not a threat to well designed damped structures.
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