Neotectonic study of the Santa Marta Fault System, Western foothills of the Sierra Nevada de Santa Marta, Colombia

The Santa Marta Fault System (SMFS) is a NNW-striking major structural feature that controls the western foothills of the Sierra Nevada de Santa Marta (SNSM), the world’s highest coastal relief. Morphotectonically, the SMFS exhibits an arrangement of parallel to subparallel fault traces. These traces display features such as offset streams and other morphotectonic indicators suggesting a left-lateral component of displacement. Related structures include NE-striking reverse faults and anticlines, and NW-striking normal faults. These structures are consistent with a model of a left-lateral shear zone striking NNW. An unlithified ruditic deposit of probable Quaternary age exhibiting tectonic deformation crops out at the Riofrío site. It consists of a series of debris slope layers that make up a colluvial cone. The documented deformation in this outcrop is characterized by a backtilting of the sequence to the NE and by the presence of apparent dip-slip faulting. This is thought to be the side view expression of predominantly strike-slip movement. A minimum magnitude (Mw) of 6.4 was estimated for an identified faulting event based on outcrop measurements of fault displacement.