Evidencias geol\uf3gicas, geomorfol\uf3gicas y geof\uedsicas de deformaci\uf3n asociada a la falla Cerritos y su implicaci\uf3n en el peligro s\uedsmico de Morelia, Michoac\ue1n, M\ue9xico

The Cerritos fault is located SW of Morelia city, in the state of Michoac\ue1n, M\ue9xico. The fault belongs to the western part of the Morelia-Acambay Fault System, an area with several active segmented faults that form various grabens and half-grabens. In this area, faulting affects Miocene to Holocene lithologies; some of these faults even control the distribution of regional monogenetic volcanoes. This work is an interdisciplinary approach to characterize the Cerritos fault, an important structure with a high seismic hazard potential. The Cerritos fault is a 12 km-long oblique fault (normal-left lateral) with a 130\ub15 m-high topographic relief (100 m of surface displacement + 30 m of subsurface displacement estimated from the inverted resistivity study). This fault is ENE-WSW oriented (255\ub0), with a 76\ub0 NNW dip. In a well\u2010exposed cross section of the Cerritos fault, a few meters from the master fault trace, a colluvial wedge with organic material was identified, yielding a radiocarbon age of 3.37-3.21 cal ka BP. Our geologic and geomorphological analyses indicate that the Cerritos fault is a young, tectonically-active fault, especially in its eastern part. The vertical and horizontal linearity of the fault scarp and the accumulation of lake deposits in the down-thrown block suggest active vertical motion (uplift and subsidence, respectively) along this fault. Geophysical surveys, including seismic refraction, terrestrial magnetometry, and electrical resistivity tomography, show the subsurface geometry of the fault to be characterized by a main listric fault plane and a damage zone in the footwall block, extending as far as 75 m from the main scarp. The damage zone is characterized by secondary, synthetic, and antithetic faults, forming roll-over anticlines and two crestal collapse grabens that accumulate colluvial material. Paleoseismic estimates of activity and seismic hazard potential indicate that the Cerritos fault has a slip-rate of 0.03\ub10.01 mm/yr, with mean vertical displacements of 0.5 m per event and a mean recurrence interval of 16 700 years. The Cerritos fault can generate single-segment ruptures with magnitudes of MW 6.2 to 6.6. Still, in a worst-case scenario, it could also rupture with the subparallel and adjacent Morelia and Cointzio faults, generating earthquake magnitudes up to MW 6.9

Geomorphic characterization of faults as earthquake sources in the Cuitzeo Lake basin, central Mexico

The Trans-Mexican Volcanic Belt is an active continental volcanic arc characterized by several arc-parallel Miocene-Holocene tectonic lake basins, such as the Cuitzeo, Zacapu, Chapala, and Zacoalco. Normal faults and related continental seismicity shape these basins. In the central part of this volcanic arc, the Cuitzeo Lake basin presents neotectonic fault activity, accommodating oblique extension through ENE-striking normal fault zones of the Morelia-Acambay Fault System and transfer faulting. Specific faults have been described in the basin, and various geological and structural studies have outlined its kinematics and structural geometry. However, these fault zones have not been fully characterized. Characterizing earthquake sources in the Cuitzeo Lake basin is essential to constrain the regional potential seismic hazard, aiming toward better territory planning. This study presents the first regional fault compilation in the Cuitzeo Lake basin that characterizes 21 fault zones from geomorphic data. We integrated previous volcanic and tectonic studies with new geomorphic and paleoseismic evaluations to assess potential seismic sources in the Cuitzeo Lake basin. Furthermore, we evaluate fault zone segmentation, fault slip distribution, transtensional partitioning, seismic hazard implications, and basin development. We improved the current understanding of the basin\u2019s transformation, subsidence, and sedimentation with all this information. Here, fault zones present a mean vertical slip-rate of 0.17 \ub1 0.27 mm/yr for 1 Ma, capable of generating Mw 6.2 to 7.0 earthquakes and average single-event displacements from 0.2 to 1.2 m. Multi-fault ruptures could be up to 63 km-long, capable of generating Mw 7.0 to 7.2 earthquakes, representing an important regional seismic hazard