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Earthquake Rupture Dynamics



Seismic hazard estimates, currently based on a sparse catalog of strong ground motion records from stations close to large earthquakes, will increasingly be based upon realistic simulations of hypothetical ruptures. These models account for the transport of heat and fluids within the fault zone, dramatic weakening of fault friction during rapid slip, and inelastic deformation of heavily fractured rocks surrounding the fault core. One current focus of the group is exploring how geometric complexity of faults, in the form of fractal surface roughness as well as branches and bends, affects earthquake dynamics. These features lead to irregular rupture propagation and the generation of incoherent high frequency seismic waves that are ubiquitous in seismograms. The image shows results from a rough fault model. The colored regions surrounding the nonplanar fault (red line) are areas that experienced inelastic deformation during the rupture process, and the blue trace is a velocity seismogram recording the history of shaking at the station (red triangle). Another focus of the research group is the development of numerical methods for computing the growth of ruptures from nucleation regions at the scale of a few meters to fully developed earthquakes that propagate tens or hundred of kilometers -- all without making compromises in parameter values constrained by laboratory studies.