Abstract:

In this study the Navarro Fault System is defined based on geologic, geomorphologic, and seismological observations. This fault system is located between the northern slopes of the Talamanca cordillera and the southern and southeastern slopes of the Irazu and Turrialba volcanoes and is characterized by left-lateral displacements. The Navarro fault system trends between east-west and northeast-southwest and includes the following fault segments: Tarrazu, Navarro, Cachi, Urasca, Paraiso, and Maravilla. There are two transtensional structures along the fault system: the step over Estrella and the Ujarras tectonic depression. Earthquakes during 1973-2015 were relocated illuminating the fault segments of the southwest portion of the system. The focal mechanisms calculated mainly correspond to strike-slip faults in agreement with morphotectonic observations.

Keywords: Morphotectonics; neotectonics; structural geology; seismicity; Costa Rica