Active faults of El Salvador



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Martínez Díaz, José J. and Álvarez Gómez, José Antonio and Staller, Alejandra and Alonso Henar, Jorge and Canora Catalán, Carolina and Insúa Arévalo, Juan Miguel and Tsige Beyene, Meaza and Villamor Pérez, María Pilar and Herrero Barbero, Paula and Hernández Moreno, Catalina and Hernández, Walter and Hernández, Douglas and Marroquín, Griselda and Mixco, Luis (2021) Active faults of El Salvador. Journal of South American Earth Sciences, 105 (103038). ISSN 0895-9811

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In this work we present a review of the current state of knowledge of the active faults in El Salvador and its seismo-tectonic implications. An updated map of active fault traces is combined with the spatial analysis of shallow seismicity, focal mechanisms, recent geodetic GPS velocities, local strain estimations and morpho-tectonic features to provide a synoptic view of the active tectonics of the El Salvador. The major faults selected as potential seismic sources bound tectonic blocks or regions that include GPS sites with consistent relative velocity vectors. We propose several active tectonic domains along El Salvador controlled by three current deformation regimes: a crustal block in the forearc sliver dominated by rigid westward translation with the faster and more homogeneous GPS velocities; three zones dominated by E-W distributed extensional coaxial deformation; and two bands with a deformation compatible with transtensional regime. In the Western sector of the ESFZ, GPS velocities and local structure suggest that E-W extension concentrates along the NNW-SSE oriented Santa Ana volcanic axis and it could connect to the north with the extensional region of the Ipala Graben. This is consistent with to the eastward shift of the North America-Cocos-Caribbean triple junction and “the closing of the zipper” proposed in recent models that progressively slows down the strike-slip movement along the northern limit of the forearc sliver. In the central sector large GPS velocity gradient parallel to the volcanic arc may be associated to complex and discontinuous structure of the ESFZ driving slowdown of the westward movement of local tectonic blocks. The southeaster sector of the ESFZ is an incipient large pull-apart structure affecting a pre-existing extensional N-S oriented fabric that induces two tectonic subdomains, the eastern one undergo E-W coaxial extension and the western one characterized by transtensional strain regime. We propose a new structural segmentation of the ESFZ considering that this fault zone includes all those structures that accommodate the relative velocity between the forearc sliver and the Chortís block. The 38 active faults with surface traces that are mapped for more than 5 km long proposed in this work, with maximum potential magnitude Mw ranging from 5.98 to 7.94, will contribute to improve regional and local seismic sources databases and seismic hazard assessment.

Item Type:Article
Uncontrolled Keywords:Active fault, El Salvador Fault zone,Central America volcanic arc, Seismic hazard,
Subjects:Sciences > Geology > Geodynamics
ID Code:63531
Deposited On:13 Jan 2021 15:51
Last Modified:25 Feb 2022 08:52

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