Tsunami potential from local seismic sources along the southern Middle America Trench

Abstract

The Middle America convergent margin is capable of generating tsunamigenic earthquakes as portrayed through historical data. However, historical tsunamigenic sources appear to be unevenly distributed along the Middle America convergent margin. The last significant tsunami generated along the southern segments of this convergent margin occurred in 1992 causing 10-m run-up in Nicaragua. In particular, the Costa Rican Pacific coast has not clear evidences of significant wave heights or local tsunami events. Partly this could be explained by the lack of historical data since paleotsunami information is not available; thus, no tsunami data beyond 500 years could be found. Nevertheless, large rupture areas or shallow ruptures offshore Costa Rica cannot be neglected. We hereby present the results of numerical simulations aimed to assess the tsunamigenic potential of seismic sources offshore southern Central America. Our approach follows the deterministic method where earthquake maximum credible scenarios are assessed. We assumed hundreds of fault ruptures to obtain surface displacement and tsunami wave heights at the shoreline to assess the tsunami threat along south Nicaragua and Costa Rica. These fault scenarios are based on historical earthquakes as well as on the newest geodetic studies that provided slip deficit. Shallow part of locked segments in this region could release accumulated stress in the near future and may generate tsunamis similar to the 1992 Nicaragua M w 7.6 and 2012 El Salvador M w 7.4 tsunami earthquakes. The numerical simulations presented in this study show that maximum wave heights up to 2–6 m could affect the southern Pacific coast of Central America even when moderate-to-large M w 7.0–8.0 interplate or outer rise earthquakes occur.