Locking-derived tsunami scenarios for the most recent megathrust earthquakes in Chile: implications for tsunami hazard assessment

Abstract

The ever-increasing data from continues geodetic networks has allowed to reveal first-order spatial relations between pre-seismic highly locked zones on the interface and regions of large coseismic slip. Here we use a distribution of locking degree and recurrence of historical earthquakes along the Chilean subduction zone to estimate the slip deficit accumulated since previous tsunamigenic earthquakes and use these constrains to simulate tsumani signals. We generate tsunami models for the recent five major tsunamigenic earthquakes in Chile during the last decade: Maule (2010), Pisagua (2014), Illapel (2015), Melinka (2016) and Valparaiso (2017). Results were compared with tsunami records to evaluate the use of locking degree as an estimate of displacement of future earthquakes and as a tool for tsunami hazard assessment. Our tsunami simulations for the Maule (2010) and Illapel (2015), earthquakes that filled a seismic gap, reproduce well the tsunami observations, for the case of Pisagua (2014), Valparaiso (2016) and Melinka (2017) although it exists a correspondence in the areas of greater degree of locking with the coseismic slip, there is also an imbalance between the energy accumulated and released in the interseismic period considered according to the historical seismicity. This indicate that the rupture of small asperities (areas that release high slip during earthquakes) may have a complex pattern of recurrence and do not fully affect a locked patch. Locking-derived tsunami scenarios represent well tsunami observations of earthquakes that ruptured a locked seismic gap, and they can be used in addition to the actual methodologies to improve the estimation of tsunami hazard.