Seismological evidence of basement and detachment fault reactivations in the northern sector of the front of the Salient of Monterrey, Sierra Madre Oriental, northeastern Mexico

This study presents seismological evidence that the northern sector of the front of the Salient of Monterrey, Sierra Madre Oriental, in northeastern México, is nowadays under tectonic compressional stress. This is derived through the seismic moment tensor inversion of two earthquakes related to a small shallow seismic sequence of four events that occurred from March 16 to 23, 2022, in southern Monterrey. The main earthquake of March 16 (Mw3.69) was felt in some cities of the Monterrey Metropolitan area. The thrust fault mechanisms of the March 16 and March 20 (Mw3.25) earthquakes had depths of 4 and 7 km, respectively, and could be linked with the reactivation of thrust faults below the boundary between the detachment horizon and the basement, which is correlated with geological evidence. For the March 16 earthquake, the nodal fault plane has the following values: strike = 158°, dip = 66°, and rake = 87°, and for the March 20 earthquake, the values were the following: strike = 146°, dip = 82°, and rake 42. These values coincide with the regional trend of the front of the Salient of Monterrey. For this area, recent seismicity recorded at the front of the fold-thrust belt shows a neotectonic compression process.