Active seismic deformation in the grabens of northern Central America and its relationship to the relative motion of the North America–Caribbean plate boundary

Abstract

The active seismic deformation along the grabens of northern Central America is calculated using a method which relates relative plate velocity with the seismic strain rate tensor. The latter is, in turn, obtained from seismic moment tensors.We calculate the typical or average moment tensor from available Centroid-Moment Tensors and fault-plane solutions. This average tensor is then used to obtain the sum of moment tensors of historical and modern earthquakes reported in the literature.Both historical and modern earthquakes yield an average extension rate of 8mm/yr along the grabens of northern Central America, while the relative motion between the North America and Caribbean plates expressed along the Motagua–Polochic fault system is 20mm/yr.This result suggests that part of the seismic deformation related to the plate boundary is taken up as extension along the grabens, which play the role of fault termination structures for the Motagua–Polochic system.