Faulting processes of historic (1917-1962) M >= 6.0 earthquakes along the north-central Caribbean margin

The plate boundary along the north-central Caribbean margin is geologically complex. Our understanding of this complexity is hampered by the fact that plate motions are relatively slow (1 to 2 cm/yr), so that recent seismicit y often does not provide a complete picture of tectonic deformation. Studie s of the faulting processes of instrumentally recorded earthquakes occurrin g prior to 1962 thus provide important information regarding the nature and rate of seismic deformation within the region, and are essential for a com prehensive assessment of seismic hazard. We have conducted body waveform mo deling studies of eight earthquakes which occurred along the north-central Caribbean plate margin, extending from southeastern Cuba to the Swan Island fracture zone (75 to 83 degrees W). None of these earthquakes has been pre viously studied and several occurred in regions where no recent (post-1962) seismicity has been recorded. The plate margin in the western portion of o ur study area is characterized by a transform fault-spreading center system . In the central and eastern portions of our study area the plate margin is a complex, diffuse region of deformation that couples transform motion in the Cayman trough to subduction along the Lesser Antilles are. Our results show that the western portion of the study area has only experienced large strike-slip earthquakes. Off southeastern Cuba two earthquakes appear to ha ve occurred on high angle, northward dipping, reverse faults with south to southeastward directed slip vectors. An earthquake in northern Jamaica in 1 957 shows pure strike-slip Faulting, most likely along an east-west trendin g fault. Finally, an unusual sequence of events located in the Pedro Bank r egion similar to 70 km southwest of Jamaica has a mainshock with a reverse- oblique mechanism, suggesting continuity of the plate interface dress field well south of the northern Caribbean margin.