Neotectónica y Geofísica de la Falla Aguacaliente en los Valles de Coris y de El Guarco, Costa Rica

In the Coris and Guarco valleys, we conducted geomorphic and geophysical studies and compiled geo-logical, hydrogeological and trench information in order to define the traces of the Aguacaliente fault. The principal active trace of this fault trends west-northwest and is located in the southern sector of the Coris and El Guarco valleys. Rivers and creeks bending between 50 and 450 m suggest it is a sinistral fault. The location of the fault trace is well constrained in certain parts of both valleys; elsewhere the fault trace is inferred using geomorphic criteria. The fault trace shows a wide deformation zone that covers between tens of meters to more than hundred meters. The lack of fault prominence and the wide fault zone are explained by the combination of a horizontal displacement fault traversing a topographically flat region with a Quaternary sedimentary fill, poorly consolidated in its upper portion, and erosion and sedimentation rates that are greater than the rate of seismic activity along the fault.

A second west-northwest fault trace is defined along the northern border of the Coris valley on the boundary of the Carpintera hills. To the east, this fault trace appears to end in a series of short northeast-trending faults. Along with geomorphic data and an interpretation of magnetic data, the fault traces suggest a normal component of displacement. These traces could be inactive.