Preliminary results on the characterisation of the Guaycume fault (El Salvador) from geodetic and seismological data

The Guaycume fault is a right-lateral strike-slip structure located in Western El Salvador, within the El Salvador Fault Zone (ESFZ). The ESFZ consists of a strike-slip fault system extending through the Central American Volcanic Arc, on the western margin of the Chortís block, where the Cocos plate subducts under the Caribbean plate.

The Guaycume fault has been proposed as a possible source for the Mw 6.4 1917 El Salvador destructive earthquake, presenting high seismic potential in close proximity to San Salvador (Alonso-Henar et al., 2018). Its geomorphological expression has been clearly identified (Martinez-Diaz et al., 2016); however, few specific studies are currently published, and its behaviour and kinematics remain widely unknown. Notably, there is a lack of precise information about the amount of deformation that this fault currently absorbs of the westward movement (relative to the Chortís block) of the forearc sliver.

We process GNSS data in the area from 2007 to 2020 in order to retrieve the GNSS velocity field surrounding the Guaycume fault. We use these data to perform a thorough kinematic study, updating the previously existing slip rates (Staller et al., 2016). Combined with seismological data, this information allows us to understand the seismic cycle of the fault to a better extent, thus leading to a better comprehension of its seismic potential.