Tomografía sísmica en la caracterización de la mega falla Puná-Pallatanga-Cosanga-Chingua

Abstract

Subduction of the Nazca oceanic plate under the South American plate and the obliquity of this subduction has generated the NE movement of the Astilla Norandina (NAS) whose eastern limit in Ecuador is the Chingual-Cosanga-Pallatanga-Puná mega- fault (CCPP). The CCPP is a strike-slip fault system and its segments represent some of the most active intra-continental seismic structures in Ecuador. This study provides thefirst tomographic images of the cortex along the CCPP to contribute to the characterization of its geometry. In order to achieve this objective, seismic data, seismic wave velocity models, topographic and geological maps were used. The geometric characteristics of the fault segments were obtained by travel-time tomography. Tomography of the Puná and Chingual segments shows almost vertical dipping angles. The southern section of Pallatanga shows a dipping angle of 75 ° oriented to the west and increases to a near vertical dip to the north. The Cosanga segment isthe only reverse segment of the CCPP. The convergence of two faults that make up this segment could be related to the superficial landslide of the Bermejo River. The Chingual segment advances N-NE and marks the separation between sedimentary and metamorphic lithologies. This investigation presents images of the crust in depth for the CCPP mega fault and the associations with the lithology of its segments to offer a complete interpretation of the geometry and seismicity of this fault system.