Indicative Structures of Paleoseismicity in the Acequion River Valley,San Juan Province,Central-Western Argentina

Evidence for paleo-seismicity has been discovered in the Acequión river valley, in West central Argentina. Two Holocene rock avalanches have been observed; the most recent of these dammed a lake, whose sediments contain liquefaction structures. At least five paleo-earthquakes affected this region during the late Quaternary, as deduced from the succession of their secondary effects. The magnitude and the probable tectonic source of these paleo-events are discussed. The observed liquefaction features associated with slumps, joints, fractures, and faults, should be generated by M>5 earthquakes related to the nearby quaternary Cerro Salinas fault, which belongs to the Eastern Precordillera fault system. These data extend the regional seismicity record to the Holocene and highlight the high seismic hazard in this part of Argentina.