Influence of Dip and Velocity Heterogeneity on Reverse- and Normal-Faulting Rupture Dynamics and Near-Fault Ground Motions

Abstract

We investigate the influence of fault dip (35°–60°) and crustal velocity heterogeneity on rupture dynamics and near-fault ground motions from normal- and reverse-faulting. The same initial conditions were used, except for the direction of initial shear stress, in each dynamic rupture calculation. We used two 3D elastic finite-element approaches that employ split nodes for the computations. In homogeneous and weakly heterogeneous half-spaces with faults dipping ≲50°, maximum fault-normal peak velocities occurred on the hanging wall. However, for fault dips ≳50°, maximum fault-normal peak velocities occurred on the footwall. Bilateral and unilateral rupture simulations in weakly heterogeneous media found that reverse-faulting slip velocities (frequency band 1–3.5 Hz) were on average 39% larger than those during normal faulting. However, on average reverse-faulting slip velocities were only 16% larger than normal-faulting slip velocities for frequencies 50°.