Comparison Between Tsunami Signals Generated by Different Source Models and the Observed Data of the Illapel 2015 Earthquake

Abstract

A major interplate earthquake occurred on September 16th, 2015, near Illapel, central Chile. This event generated a tsunami of moderate height, however, one which caused significant near field damage. In this study, we model the tsunami produced by some rapid and preliminary fault models with the potential to be calculated within tens of minutes of the event origin time. We simulate tsunami signals from two different heterogeneous slip models, a homogeneous source based on parameters from the global CMT Project, and furthermore we used plate coupling data from GPS observations to construct a heterogeneous fault based on a priori knowledge of the subduction zone. We compare the simulated signals with the observed tsunami at tide gauges located along the Chilean coast and at offshore DART buoys. For this event, concerning rapid response, the homogeneous source and coupling model represent the tsunami at least as well as the heterogeneous sources. We suggest that the initial heterogeneous fault models could be better constrained with continuous GPS measurements in the rupture area, and additionally DART records directly in front of the rupture area, to improve the tsunami simulation based on quickly calculated models for near coastal areas. Additionally, in terms of tsunami modeling, the source estimated from prior plate coupling information in this case is representative of the event that later occurs; placing further importance on the need to monitor subduction zones with GPS.