A seismotectonic model for the Chortís Block

Abstract

AbstractI propose a new seismotectonic model for the Chortís Block, at the northwestern corner of the Caribbean Plate. Shallow seismicity in the area clearly shows three zones of deformation: one along the North America–Caribbean Plate boundary and another along the Central America volcanic arc, and one in the area of the grabens of northern Central America. Analysis of Centroid moment–tensor solutions for shallow earthquakes in these three area show thatTor tension axes are horizontal and trend away from the corner, and thatPor compression axes for the plate boundary and the volcanic arc are also horizontal and trending towards the corner. Calculation of seismic moment release per unit volume reveals similar values for the volcanic arc and the plate boundary. The state of stress and similarity in seismic moment release suggest that the Chortís Block is being extruded towards the ESE. This is probably due to compression of the large North America and Cocos Plates that surround it.