The main structural elements, seismicity and focal mechanisms from the northern terminus of the Panama Fracture Zone, Southwestern Panama, are analized. This is one of the main seismic sources of the Isthmus of Panama and the Central American region. Based on the focal mechanisms of the July 31, 2002 Earthquake and its main aftershocks, plus their spatial distribution it is confirmed that the Panama Fracture Zone extends inland along the axis of the Burica peninsula. This seismic source is a very important element to be taken into account for every seismic hazard evaluation at Western Panama and Southern Costa Rica.