Kinematic and dynamic modeling of the earthquake source: On spatial correlations of source parameters, supershear transition, and strong ground motion

Generally the most severe shaking during an earthquake occurs in the vicinity of the causative fault. However, ground motion recordings within several kilometers of large earthquakes are sparse. To provide more insight into the overall, near-fault pattern of ground motion we use numerical simulations of earthquakes. Under the major assumption that we know the spatio-temporal evolution of slip on the fault we can use kinematic models of earthquakes to simulate ground motion over a broad range of frequencies. We can better approximate the spatio-temporal evolution of slip if we understand how the physics of the earthquake process controls the faulting. Using dynamic models, which simulate the earthquake rupture as frictional sliding, we can compute the spatio-temporal evolution of slip over a limited range of frequencies. In this study we analyze more than 300 dynamic ruptures to determine the spatial interdependency of earthquake source parameters, their autocorrelation and their marginal distributions. The results are implemented in a new kinematic rupture model generator that is validated against recorded strong motion data. Using;simulations we address two important questions. First, we use kinematic models to investigate the probable cause for the observation that the peak ground motion saturates at distances close to the fault. Second, we use dynamic models to explore how the transition to supershear propagation speed and the ground motion are affected by the autocorrelation of the initial stress. We find that the stress in the Earth is highly heterogeneous with a slight correlation.