Near‐Field Effects of Earthquake Rupture Velocity Into Tsunami Runup Heights

Abstract

AbstractTsunamis have often been treated as an isolated phenomena from the earthquake itself. In tsunami modeling, seafloor deformation is generated from an earthquake. That deformation is copied into the sea surface, and then, the tsunami is propagated over the ocean. On the other hand, rupture velocities from earthquakes are in the span of 1.5–2.5 km/s; therefore, it is safe to approximate the earthquake rupture propagation as an instantaneous phenomena relative to the tsunami propagation. However, this is not necessarily true for all earthquakes. Several types of large slow earthquakes or nonregular earthquakes, such as low frequency earthquakes and very low frequency earthquakes, and tsunami earthquakes have been detected and observed in certain zones around the world. A key question is: Do giant thrust tsunamigenic earthquakes produce slow rupture (0.1–0.5 km/s) velocities? In this study, we model heterogeneous earthquakes sources using very slow rupture velocities (0.1– 2.5 km/s) with the aim of understanding how this parameter affects the tsunami propagation and runup. We compute the amplification due to a very slow moment release in megathrust earthquakes. Our research shows that rupture velocity plays a key role on runup amplification, and the classic instantaneous case might not work as expected for every case.