The Effect of Earthquake Kinematics on Tsunami Propagation

Abstract

Tsunamis are one of the most destructive effects of subduction zone earthquakes. Directly observing and understanding the generation and propagation of tsunamis remains challenging due to limited offshore instrumentation and a sparse catalog of large events. This makes linking characteristics of the earthquake rupture to their effect on tsunami generation difficult. While past studies explored how varying earthquake source geometries affect tsunami nucleation, little has been done to examine the role of the kinematic component of rupture on the tsunami; we explore these effects in this study. While past studies have examined the kinematic effect using coastal tide gauge data, we expand this examination to more recent pressure gauges. We identify a consistent rotation of the main beam of tsunami energy when using a kinematic model, affecting far-field hazards. We also identify a delay in tsunami arrival times at both coastal and open-ocean gauges that can be as long as the total source duration. For large earthquakes, this delay introduces nonnegligible mapping errors when employing open-ocean tsunami data for source characterizations. As a result of our findings we recommend including a kinematic component to tsunami modeling when studying events with source durations over 120 s and using recordings from open-ocean pressure gauges. We also find that when focusing purely on coastal gauge data and near-source hazards, the kinematic component is a much smaller contribution to the source uncertainty and can be ignored.

A Source Clustering Approach for Efficient Inundation Modeling and Regional Scale Probabilistic Tsunami Hazard Assessment

“…Seafloor deformation is directly translated to a disturbance at sea level by assuming an incompressible water column. While some large magnitude earthquakes can have rupture durations extending multiple minutes, this kinematic effect on the tsunami in the near-field is minimal (Satake, 1987;Williamson et al, 2019). Here, we simplify the rupture process by treating all seafloor deformation as instantaneous and occurring at the initial time step of our tsunami model.…”

Relative Tsunami Hazard From Segments of Cascadia Subduction Zone For Mw 7.5–9.2 Earthquakes

“…Our arbitrary choice of rupture directivity (north to south) has little effect because the proximity of the coastlines to the trench (∼150 km) and the large dominant wavelength of the tsunami (Rabinovich, 1997) prevent the rupture duration from significantly affecting the coastal tsunami amplitudes. Numerical experiments with various modes of rupture in flat oceans and near coastlines of different morphologies reveal that the contribution of rupture directivity is not significant in the near field (Figure S3), as also shown by Williamson et al (2019). One can show that (see Supporting Information) in the absence of small-scale disturbances at narrow openings, the internal structure of ruptures in deep oceans is practically not transferred into shallow basins.…”

A numerical study of SMART Cables potential in marine hazard early warning for the Sumatra and Java regions

“…This algorithm computes surface deforma-tions from a uniform slip field on a buried inclined fault in a half-space. The choice of static over kinematic sources was made due to the small effect of rupture kinematics in the near-field (Williamson et al, 2019;Salaree et al, 2021).…”