The strength of faults derived from 3-D fault imaging and tectonic computer simulations of the lithosphere

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The strength of faults in the Earth s crust and lithosphere is one of the most important parameters to assess earthquake hazard and risk. Yet, to date a fundamental understanding of fault strength has remained elusive, as numerous observations have pointed to faults being much weaker than predicted by basic theory. The proposed project will advance our understanding of fault strength. The basic hypothesis is that geometry and interaction among faults govern their strength. To test this hypothesis the project will focus on well-instrumented, tectonically active regions in California and Taiwan characterized by strike slip and by thrust motion, respectively. For parts of these regions threedimensional (3-D) fault maps of unprecedented detail are already available. For other parts these will have to be constructed. I will integrate constraints from seismology, tectonics, and computer modeling, and implement the 3-D fault maps into state-of-the-art tectonic computer simulations of the deformation behavior of the Earth s crust and lithosphere. The simulations will be validated against tectonic and geodetic measurements of crustal deformation to constrain fault strength parameters. In addition to answering the fundamental question of how large fault systems interact, the expected results wilt help improve considerably the realism of earthquake scenario calculations.