2D GRAVITY MODELING OF THE COCOS-NORTH AMERICAN PLATE INTERFACE ALONG THE GUERRERO SEISMIC GAP
The geometry of the interface between tectonic plates in subduction zones plays a crucial role in tectonic kinematics. In the Guerrero seismic gap (GGap), the subduction geometry of the Cocos plate beneath the North American plate exhibits a clear relationship with the occurrence of large earthquakes, slow slip events, and non-volcanic tremors, increasing both seismic and tsunamigenic potential. Should a major earthquake occur, it could reach magnitudes of Mw 8.1–8.4 (Suárez et al., 1990), with the potential to devastate cities such as Acapulco and Mexico City.
Previous studies estimating the subduction angle of the Cocos plate using seismological data (Pardo and Suárez, 1995; Pérez-Campos et al., 2008; Kim et al., 2012) suggest a shallower slab geometry compared to recent seismic relocations derived from SSN and OBS data. These discrepancies may significantly influence seismic hazard assessments and the understanding of the seismic cycle (Pérez-Silva et al., 2021).
Given these considerations, we incorporated existing gravity data (Kostoglodov et al., 1996) with new data collected along the continental zone of the GGap. This gravimetric survey followed perpendicular profiles to the coastline, complementing previous data. The data were carefully treated by applying instrumental corrections and reductions to derive gravity anomalies. We used the updated seismic locations and regional densities from Kostoglodov et al. (1996) and Campos-Enríquez & Sánchez-Zamora (2000) as constraints to model the subduction interface geometry. The initial forward model was further refined through inversion using the PyGIMLi framework (Rücker et al., 2017).
We present an updated geometry of the interface along the GGap that explains the gravity data and the recent earthquake relocations. This geometry will be used to improve the seismic hazard assessment through seismic cycle modeling.