Anatomy of Strike Slip Fault Tsunami genesis

Tsunami generation from earthquake induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been believed as insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the emergence of large tsunamis (>1m) under rather generic conditions. In this work, we present a physics driven computational framework that couples models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time dependent ground motions from the spontaneous dynamic ruptures are used as the driving boundary motions in the tsunami model. Our results indicate that strike-slip faults have the unexpected potential for generating devastating tsunamis under the proper conditions. We show that supershear ruptures propagating along strike-slip fault, traversing narrow and shallow bays generate significant horizontal motions that can be a critical driver of tsunami hazard. Our work identifies intrinsic mechanisms for considerable tsunami generation, without necessarily having co-seismic underwater landslides or slumps. The tsunami model points out to three different phases in the tsunami motion; an instantaneous dynamic phase, a lagging coseismic and a classical postseismic phase, each of which may affect coastal areas differently. In addition to supershear rupture, we evaluate the case of sub-Rayleigh rupture propagating along the same strike-slip fault and demonstrate that supershear rupture generate significantly higher water wave amplitude. Finally, we highlight the important role bathymetry motion have on the tsunami generation by comparing a basin like bathymetry versus a uniform depth bathymetry.