The focal mechanisms of five small earthquakes (4.9?mb?5.6) that occurred in northwestern Venezuela have been determined using teleseismically recorded Rayleigh waves. The Rayleigh wave data were also used to constrain the depths of the five events studied. These results suggest that the southern boundary of the Caribbean plate is presently characterized by a broad zone of internal deformation where the eastward displacement of the Caribbean plate with respect to the South American plate is being accommodated along variously oriented strike slip faults. This strike slip faulting appears to occur along preexisting zones of weakness such as the Bocono fault, and the earthquakes studied here are all consistent with an east--west trending compressive stress field being released along these zones of weakness. These focal mechanisms, therefore, reflect the tectonic stress field generated by the eastward motion of the Caribbean plate as opposed to relative plate motion per se. Thus, the southern boundary of this plate cannot be classified as a simple plate boundary (i.e., transform fault, spreading center, or subduction zone). Instead, relative plate motion in this region appears to be accommodated by internal deformation within a broad zone extending from the interior of the Caribbean plate into northern South America.