Push-pull driving of the Central America Forearc in the context of the Cocos-Caribbean-North America triple junction.

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.

Main crustal seismic sources in El Salvador.

We present a map and a data set containing information about intra-plate seismic sources in El Salvador. These are the results of the field campaigns and data analysis carried out by the research group of Planetary Geodinamics, Active Tectonics and Related Risks from Complutense University of Madrid during the last 12 years. We include two maps, the first map contains 1405 fault traces with evidences of Quaternary activity derived form morphometric, paleoseismological and geomorphological analysis together with field data mapping carried in El Salvador. The second map is a synthesis of the 29 intra-plate seismic sources selected from the quaternary faults map. The geometry of these sources was simplified and we also include a table where some available data of the proposed sources are included, such as their name, orientation, length and slip-rate. For further interpretation and discussion of these sources see (Alonso-Henar et al., 2018) [1, doi.org/10.1016/j.enggeo.2018.06.015].