In this work we present morphological, earthquake and GPS seismology observations that evidences the presence of active and seismogenic submarine faulting in the Archipelago of San Andres, Providencia and Santa Catalina (ASAPSC) and surrounding areas in western Caribbean. The analysis of recent acquired multibeam bathymetry and regional seismic profiles allowed the identification and mapping of several fault systems (Albuquerque-Providencia, Pedro, Hess, Roncador and Serrana fault systems), which are recognized as very clear and strong lineaments on the seafloor. Regionally, these structures are responding to a transtensional tectonics evidenced by the presence of several elongated and narrow pull-apart basins (Providencia, Albuquerque Nutibara, Guambiano and Cunas depressions) bounded by rectilinear seafloor scarps. The occurrence of shallow earthquakes with Mw>5 (e.g., 1926 Mw 6.9, 1995 Mw 5.7, 2002 Mw 5.7, 2014 Mw 5.3, and 2018 Mw 5.6 and 6.1) is not unusual in this sector of the Caribbean and proves the seismogenic potential of the fault systems identified in the ASAPSC. These seismic events are clearly related to the fault traces mapped and the available focal mechanisms confirm a primarily strike-slip kinematics. In particular, we made a preliminary analysis of the 2018 Mw 6.1 earthquake with epicenter located 25 km to the southeast of Providencia which caused slight damage in this island and was widely felt in San Andres. The GPS seismology analysis of the data registered by the station CN35 located in Providencia Island, installed by the COCONet project and operated by the GeoRED Project of the Geological Survey of Colombia, clearly shows the coseismic displacement in response to the Mw 6.1 earthquake of the order of 8 mm to the north and 11 mm to the west; the vertical component is negligible. This observation, in combination with the earthquake focal mechanism, indicate that the causative structure would correspond to a NW-SE-oriented fault with a predominantly right-lateral behavior. These preliminary results highlight the importance of carrying out multidisciplinary studies for the characterization of active faults and their seismogenic potential in offshore areas.
- Javier Idárraga-García (*), Eliana Gómez-Hurtado (**), Héctor Mora-Páez (**)
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