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Successive collapses of the El Estribo volcanic complex in the Pátzcuaro Lake, Michoacán, Mexico

2014; Elsevier BV; Volume: 289; Linguagem: Inglês

10.1016/j.jvolgeores.2014.10.011

1872-6097

Antonio Pola, José Luis Macías, Víctor Hugo Garduño‐Monroy, Susana Osorio-Ocampo, Silvestre Cardona-Melchor,

earthquake and tectonic studies

Abstract The El Estribo volcanic complex is located in the north-central part of Michoacan State (Mexico) within the Michoacan–Guanajuato Volcanic Field. It consists of a ~ 126 kr shield volcano crowned by a cinder cone, separated by a paleosol dated at 28,360 ± 170 BP. The shield volcano has been cut by the E–W normal Patzcuaro fault that exposes 200-m of piled up lavas flows. Our field reconstruction suggests that two collapses have been originated from this fault. Two debris avalanche deposits with hummocky topography are exposed between this fault and the southern shore of the Patzcuaro Lake. The basal debris avalanche deposit (BDAD) covers lacustrine sediments and is covered by a paleosol that at 28,110 ± 720 yr BP yielding a minimum age for the event. It had a maximum run out of 3.2 km with a H/L of 0.0062. The upper debris avalanche deposit (UDAD) is overlain by a paleosol dated at 14,110 ± 60 yr BP that yields a minimum age of the event. It had a maximum run out of 2.3 km with a H/L of 0.0086. No pyroclastic deposits have been found in association with these debris avalanches and the shield volcano rocks show signs of intense hydrothermal alteration or abundant clay minerals for which we assume that failure was triggered by seismic–tectonic activity. The older debris avalanche was more mobile because it moved on water and on top of water-saturated sediments deforming them and likely originating a tsunami across the lake. Instead, the younger debris avalanche moved across the previous rugged hummocky topography of the basal avalanche resulting in a more restricted dispersion. These collapse events of El Estribo, the morphology of the scarp and historic and modern seismicity indicate that a future failure represents a serious threat to the surrounding communities of the Patzcuaro Lake. Consequently, some preventive measurements as seismic and deformation rate monitoring are necessary. Today five villages with circa 1500 inhabitants live upon the mass waste deposits.