Beyond the Motagua and Polochic faults: Active strike-slip faulting along the Western North America-Caribbean plate boundary zone

I investigate the role of two strike-slip faults in the tectonics of the western North America-Caribbean plate margin. The Ixcan fault, located in Guatemala north of the Polochic fault, is seismically active, with earthquakes of magnitude up to 5.7 reported recently. Fault-plane solutions along this curvilinear but generally E-W trending fault indicate left-lateral, strike-slip displacement. Several historic earthquakes appear to have taken place along the Ixcan fault since 1728, the largest one being the 1816 event (M=7.5). The NW-SE trending Concordia fault in southeastern Mexico appears to be the site of the great (M=7.6) earthquake of 1902. Isoseismals for this event suggest shallow, left-lateral strike-slip faulting. I propose a seismotectonic model in which both faults are part of the deformation associated to the North America-Caribbean plate boundary zone. Transpressive structures are found in the fault steps between strike-slip fault systems. (C) 2010 Elsevier B.V. All rights reserved.