Neotectonics of the Ochomogo and Capellades faults and its relation with the Aguacaliente fault system, southern slopes of the Irazú-Turrialba massif, Costa Rica

摘要

Geomorphic studies supplemented with geological information allow us to define the predominantly left-lateral strike-slip Capellades and Ochomogo faults. The  Capellades fault connects with the Aguacaliente fault through the Cartago transpressive zone, including E-W folds and oblique (reverse-left lateral) faults. The Ochomogo fault is located between south San José and the southern slopes of the Irazú Volcano, is about 22 km long, and has a nearly left lateral strike slip along its E-W trend to an oblique (normal-left-lateral) slip along its ENE trending part. The interaction between the Ochomogo and Aguacaliente faults results in a transtensional regime that formed the Coris and Guarco valleys. The Capellades fault trends ENE to NE, is about 25 km long, and is located in the southern and southeastern slopes of the Irazú and Turrialba volcanoes. Several geomorphic features show between few meters to 0.67 km of left-lateral displacements along the Capellades fault trace. Based on the Middle-to-Late Pleistocene geological units exposed on the S-SE slopes of the Irazú Volcano, the fault slip rate is estimated to be between a minimum of 0.5 mm/yr and a maximum of 1.1-3.3 mm/yr.