The Santo Domingo fault system, Galeana (Nuevo Leon): evidence of neotectonics between the Sierra Madre Oriental and the Basin and Range provinces and hazard implications for northeastern Mexico

Neotectonic activity in the western margin of the Sierra Madre Oriental in northeastern Mexico was evaluated using geomorphological, geological, structural, and seismological analyses. We evaluated recent tectonic evidence in the basin of the Potosí Valley related to the Santo Domingo Fault System (SDFS), which is one of the largest active extensional fault zones documented so far in the transition zone between the Basin and Range and the Sierra Madre Oriental provinces. Two indices were used in the geomorphological analysis: transverse topographic basin asymmetry ( T ) and mountain front sinuosity ( Smf ). The results show that the studied basin is slightly tilted to the WSW, consistent with the typical basin deformation pattern in the Basin and Range province. Structural data collected in the field unveil a NW–SE striking fault system, geometrically and kinematically similar to the Cenozoic lineaments of the Basin and Range province. The local stress tensor calculated in this study indicates an extensional tectonic regime, suggesting S_V > S_NW > S_NE . Analysis defines an azimuth trend of 298° and 036° for σ_2(S_Hmax) and σ_3(S_hmin) , respectively. According to the results, the SDFS is well orientated for possible future reactivation as a normal fault system. We estimate that a segmented rupture of the SDFS could produce seismic events on the order of magnitude 5 < M w < 6 . Considering a continuous rupture ( 42 km) of the SDFS in a single event, an earthquake of M w 7.0 could be expected. The results are essential to estimate seismic hazards in northeastern Mexico, including important urban areas, such as Monterrey, Nuevo León, and Saltillo, Coahuila.