Abstract
A seismic swarm of tectonic origin affected the area of Puriscal and sourroundings in 1990. For this reason, an area of 250 Km2 has been selected for detail mapping.
The geological map show that the area is formed by lithological units varying in age from the Miocene to Recent. The structural features show that main faulting is NW-SE and ins expressed on strike slip dextral faults. Another faulintg is transtensional N-S and siniestral NE-SW strike slip.
Statistical analysis of focal mechanism corrspond to he faults that had been identifed. Both methods show the mean direction of compression to be N10°-20°E, and it interpreted as caused by simple shear between the regional faults named Jaris and Candelaria. Hence, it is concluded that the regional compression is S-N.