EVIDENCIAS DE ACTIVIDAD PALEOSÍSMICA EN LA FOSA DE LONCOPUÉ Y FAJA PLEGADA Y CORRIDA DEL AGRIO (DEPOCENTRO DEL HUECÚ), PROVINCIA DE NEUQUÉN

ROJAS VERA, E. A.; SPAGNUOLO, M.; ORTS, D; ZAMORA VALCARCE, G.; A. FOLGUERA; RAMOS V. A.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Lugar: Ciudad de buenos Aires; Año: 2010 vol. 67 p. 163 - 176

0004-4822

Paleoseismic evidence in the Loncopué trough and the Agrio fold and thrust belt (Huecú depocenter), Neuquén Province. Liquefactedlacustrine sediments were identified at the Quaternary El Huecú depocenter, located in the central part of the retroarcLoncopé trough at the northwestern Neuquén sector. These were interpreted as seismites based on their morphological characteristics,as well as their neotectonic setting. Additionally, over the western Agrio fold and thrust belt, other similar depositswere identified. Finally, fractured gravels associated with clastic dykes are developed at the eastern Loncopué fault systembetween the previous two occurrences. A remote source is a possibility for the paleoseismic evidence. Particularly, theFebruary 27th of 2010 earthquake, the fifth earthquake in magnitude since the instrumental period of time, showed that eventhough energy arrives rather attenuated at the retroarc zone, is sufficient to generate the described liquefacted deposits. Onthe other hand, only local and strong earthquakes could generate the intruded and fractured gravels. Assuming a common andlocal seismogenic source for the described occurrences and using known empirical formulae proposed by other authors, twoareas were outlined as potential sites for seismic triggering (the El Huecú basin and the inner Agrio fold and thrust belt). Itsintersection corresponding to the eastern Loncopué fault system appears as the main potential source for seismic activity,which is compatible with previous neotectonic studies performed in this region and the occurrence of fractured gravels andclastic dykes in the area.