Landers 1992 “Reloaded”: Integrative Dynamic Earthquake Rupture Modeling

Abstract

The 1992 Mw 7.3 Landers earthquake is perhaps one of the best studied seismic events. However, many aspects of the dynamics of the rupture process are still puzzling, for example, the rupture transfer between fault segments. We present 3-D spontaneous dynamic rupture simulations, incorporating the interplay of fault geometry, topography, 3-D rheology, off-fault plasticity, and viscoelastic attenuation. Our preferred scenario reproduces a broad range of observations, including final slip distribution, shallow slip deficits, and mapped off-fault deformation patterns. We demonstrate good agreement between synthetic and observed waveform characteristics and associated peak ground velocities. Despite very complex rupture evolution, ground motion variability is close to what is commonly assumed in Ground Motion Prediction Equations. We examine the effects of variations in modeling parameterization within a suite of scenarios including purely elastic setups and models neglecting viscoelastic attenuation. Source dynamics of all models include dynamic triggering over large distances and direct branching; rupture terminates spontaneously on most of the principal fault segments. Sustained dynamic rupture of all fault segments in general, and rupture transfers in particular, constrain amplitude and orientation of initial fault stresses and friction. We conclude that physically consistent in-scale earthquake rupture simulations can augment earthquake source observations toward improving the understanding of earthquake source physics of complex, segmented fault systems.