The 1719 El Salvador Earthquake: An M>7.0 Event in the Central American Volcanic Arc?

Abstract

In the regions where few field neotectonics and paleoseismic studies have been performed (e.g., Central America), the interpretation of the seismic sources responsible for the historical (preinstrumental) catastrophic earthquakes lies almost entirely in the spatial distribution of damage interpreted from historical sources, mainly fragmentary written documents. The occurrence of catastrophic earthquakes affecting this region justifies the necessity of a deeper analysis of the geologic implications of the more significant historical earthquakes in light of the new insights. Recent advances in the identification and dating of surface‐rupture evidences along the central El Salvador volcanic arc led us to revisit some historical evidence of damage along this region and to combine geologic (paleoseismic) evidence with damage distribution.

At least 11 destructive earthquakes have occurred in El Salvador since 1900 (White and Harlow, 1993; Fig. 1). These events caused more than 3000 deaths as a consequence of strong ground motions and/or subsequent landslides (Bommer et al. , 2002). The instrumental earthquake record shows that large ( M w>7) events occurred as reverse fault events along the interface between the subducted plate and the over‐riding continental plate or as normal‐faulting events within the subduction plate resulting from extensional forces generated by slab‐pull forces or by bending of the subduction plate (Alvarez‐Gomez, 2009). Onshore, instrumental earthquakes have been reported with moderate magnitudes ( M w 7.0 usually have been assigned to the subduction zone, whereas historical records with M w 7.0) associated with the rupture of the El Salvador fault zone …