Seismicity of Valle Medio del Magdalena basin, Colombia

Abstract

An analysis of seismicity of Valle Medio del Magdalena (VMM) Basin, Colombia was done over the period between 2014 and 2017 with the aim to obtain a baseline of the seismic activity in this region. Thirteen portable broad band seismic stations were deployed during the study period and were complemented by 15 permanent broad band seismic stations. Hypocenter distribution and focal mechanism analyses were performed.Hypocenter determination was performed for 7073 earthquakes with local magnitudes between 0.1 and 5.7. Those earthquakes were located at crustal as well as subduction depths. The former were related to fault systems that evidenced seismic activity, such as the Bucaramanga fault system and the Cimitarra, Curumaní and Arrugas faults. The latter delineated the shape of the subduction slab of the Caribbean plate beneath South American plate, which exhibited changes in the dip angle between 29° and 39° probably associated to deep ruptures.Inversion of focal mechanisms obtained by first motion P-wave analysis for crustal earthquakes showed that the VMM region was under a regional strike-slip stress regime.