Velocity field for Western Venezuela: Elastic modeling in the Southern Merida Andes

Abstract

We show new geodetic velocity field for Western Venezuela based on repeated GNSS campaign measurements in 2011, 2013, and 2016. The 28 sites are distributed on the northern side of the Oca-Ancon fault, the eastern Maracaibo Block, and vicinities to the whole extension of the Boconó fault but particularly densified across the La Grita segment in the Southern Mérida Andes. Deformation in western Venezuela based on geodetic measurements has been the object of recent studies, however this contribution focuses on the Southern Merida Andes. We assess the simple homogeneous model for one fault (across La Grita segment of the Boconó fault) and two-faults (Boconó fault and a secondary system) model. Our preferred model of both approaches shows a far-field velocity of 11.3 mm yr-1 and a 9.6 km locking depth for the Boconó fault. Nonetheless, the best fit concerning the two-fault model shows a slip rate of 9.5 mm yr-1 for the Boconó fault and 1.3 mm yr-1 for the Caparo fault. We confirm that the Boconó fault is the main structure that accommodates most of the right-lateral slip between the Maracaibo block and South American plate. A complimentary comparison with the surface velocity model VEMOS17 indicates the need of densifying observation sites through measurement campaigns and continuous GNSS stations. These stations will improve our knowledge of local and regional geodynamics and their implications for seismic hazard studies.

Keywords

• GNSS, Tectonic deformation, Fault slip rates, Locking depth, Boconó fault, Caparo fault.