The Oblique Rupture of the Strike-Slip January 18, 2021, MW 6.4 Earthquake and Triggered Events from a Local Seismic Network (San Juan Province, Argentina)

Abstract This research covers the study of the first month of data from a local seismological network deployed after the MW 6.4, January 18, 2021, San Juan earthquake, over the central Chilean-Pampean flat slab. Almost 1000 seismic events were detected in the first month after the MW 6.4 earthquake occurred, with ML magnitude ranging from −0.2 to 4.3. The majority of the seismic events were relocated at a depth of around 14 km and distributed in a northeast–southwest direction. The focal mechanism solutions obtained represent the rupture main process with one of their nodal planes according to the epicentral distribution, from which we can define the rupture dip to 61°. On the other hand, quickly after the MW 6.4 earthquake occurred, a nearby region at shallower depths became activated, from which Differential Synthetic Aperture Radar Interferometry results show vertical movements. In the epicentral area and concordance with the northeast–southwest rupture region, we found a low of the analytical signal which extends in the same strike by approximately 80 km to the most populated region in the San Juan Province. Considering the closeness of the greatest earthquakes that shocked the eastern sector of the San Juan Province to the subducted Juan Fernandez Ridge track, and the direction of the rupture process, we infer its influence as one of the significant factors that contributes to the high seismic activity in this region.