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Different kinematic models have been proposed for the triple junction between the North American, Cocos and Caribbean plates. The two most commonly accepted hypotheses on its driving mechanism are (a) the North American drag of the forearc and (b) the Cocos Ridge subduction push. We present an updated GPS velocity field which is analyzed together with earthquake focal mechanisms and regional relief. The two hypotheses have been used to make kinematic predictions that are tested against the available data. An obliquity analysis is also presented to discuss the potential role of slip partitioning as driving mechanism. The North American drag model presents a better fit to the observations, although the Cocos Ridge push model explains the data in Costa Rica and Southern Nicaragua. Both mechanisms must be active, being the driving of the Central American forearc towards the NW analogous to a push-pull train. The forearc sliver moves towards the west-northwest at a rate of 12–14 mm/yr, being pinned to the North American plate in Chiapas and western Guatemala, where the strike-slip motion on the volcanic arc must be very small. [ABSTRACT FROM AUTHOR]

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. • Review of the current state of knowledge of the active faults in El Salvador. • Updated active faults map consistent with GPS velocities distribution. • Three current deformation regimes along the El Salvador fault zone. [ABSTRACT FROM AUTHOR]