Submarine earthquake rupture, active faulting and volcanism along the major Liquiñe-Ofqui Fault Zone and implications for seismic hazard assessment in the Patagonian AndesReportar como inadecuado




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The Liquiñe-Ofqui fault zone LOFZ in the Patagonian Andes is an active major transpressional intra-arcfault system along which Quaternary faulting and volcanism develop. Subaerial and submarine geomorphologic andstructural characterization of latest Pleistocene-Holocene faults and monogenetic volcanoes allows us to assess geologicalcartography of active faults and the kinematic model for recent tectonics during postglacial times, since 12,000 cal. yearsBP. This allows increasing the basic geological knowledge necessary for determining the seismic hazard associated withcortical structures in the Aysén region in southern Chile. Fault cartography and field observations suggest dominantdextral-reverse strike slip along north-south and locally NNW-striking faults, dextral-normal strike slip along NE toNNE- striking faults, and sinistral strike slip along east-west faults. This kinematics is consistent with regional SW-NEshortening in the context of a major transpressional fault zone. Holocene and even historic monogenetic and sub-aquaticvolcanism occurred in this tectonic setting in a close spatial relationship and probably favored by the activity and localarchitecture of faults. Submarine fault scarps and deformed sediments observed at the bottom of the Aysén Fjord wereassociated with the destructive April 2007 Mw6.2 earthquake located along the LOFZ. Our observations show thatthis earthquake occurred along dextral 15-20 km long N-S structure named Punta Cola Fault PCF. This fault systemis located some kilometres to the east of the main N-S Río Cuervo Fault RCF. Most of the epicentres of the seismicswarm during 2007 were located along or in between both structures. The study area is a transference zone betweenN-S regional branches of the LOFZ. The cartography of fault segments proposed here together with geophysical andgeologic data suggest that large earthquakes Mw6.2-6.5 can be typically expected along most of the active faults. Besides,seismic hazard assessment should also consider the possibility of earthquake magnitude in the order of 7.1 alongthe main fault systems like the RCF.Nota general

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Autor: Vargas Easton, Víctor; - Rebolledo, Sofía; - Lahsen Azar, Alfredo; - Thiele Cartagena, Ricardo; - Townley Callejas, Brian; - Se

Fuente: http://repositorio.uchile.cl/



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