The Tarímbaro-Álvaro Obregón Fault, a major structure of the Morelia-Acambay Fault System in Central México

Abstract Seismic hazard assessment in central México is essential considering the numerous crustal active faults crossing densely populated cities. The Morelia-Acambay Fault System in central México comprises at least thirty active E-W normal faults that affect Miocene to Holocene units and are responsible for several devastating earthquakes. However, most of these faults are unstudied; their behavior and seismogenic potential are unknown. The ENE-striking ~ 40-km-long Tarímbaro-Álvaro Obregón (TAO) fault is one of these major tectonic structures. It is located on the northern border of the Morelia Metropolitan area, where more than one million inhabitants live within 10 km of the fault. We studied this normal fault by means of a detailed and multidisciplinary characterization due to its large surface expression and the current anthropization, which makes the use of classical techniques difficult. This study integrates geological, geophysical, seismological, and paleoseismic data, providing data for a better seismic hazard assessment. The TAO fault zone comprises three right-stepping en échelon segments separated by relay zones. This study reveals a mean vertical slip rate of 0.04 ± 0.08 mm/yr, and 1.3 m of single-event vertical displacement. The TAO fault can produce magnitude 6.2 to 7.2 earthquakes, representing a significant potential seismic source in central México.