Differences between heterogenous and homogenous slip in regional tsunami hazards modelling

Abstract

Summary The homogenous slip finite fault model is commonly used in tsunami hazards for a variety of applications. These include early warning and short-term forecasts of tsunami amplitudes, scenario ruptures for risk assessments, and probabilistic tsunami hazard analysis (PTHA). Over the last decade, however, it has become feasible to calculate stochastic slip models which reflect the expected spatial statistics of slip observed in real events. In this paper we examine the impacts of the homogenous slip model when compared to stochastic slip distributions and ask whether, in light of these technical advancements, the homogenous slip assumption remains a reasonable one. We employ a simplified subduction zone geometry, free of complex path and site effects, and study simulated tsunamis from earthquakes in the magnitude 7 to magnitude 9 range. We find that homogenous slip models have lower tsunami potential energies and frequently underpredict the peak tsunami amplitudes and the resulting tsunami hazard, particularly at low probabilities of exceedance. This finding has important implications for all tsunami hazards applications. Calculating a suite of realistic stochastic slip distributions is now within reach of tsunami scientists, thus, we conclude that use of heterogeneous slip models for tsunami hazards applications is preferable