HR: 16:20h
AN: U54B-01 INVITED     [Abstracts]
TI: Earthquakes in Fiordland, Southern Chile: Initiation and Development of a Magmatic Process
AU: * Barrientos, S
EM: sbarrien@dgf.uchile.cl
AF: Sergio Barrientos, Blanco Encalada 2002, Santiago, Chile
AU: Service, N S
AB: Several efforts in Chile are being conducted in relation to geophysical monitoring with the objective of disaster mitigation. A long and permanent monitoring effort along the country has been the continuous effort resulting in the recognition and delineation of new seismogenic sources. Here we report on the seismo-volcanic crisis that is currently taking place in the in the region close to the triple junction (Nazca, Antarctica and South America) in southern Chile at around latitude 45°S. On January 22, 2007, an intensity V-VI (MMI) earthquake shook the cities of Puerto Aysén, Puerto Chacabuco and Coyhaique. This magnitude 5 event, was the first of a series of earthquakes that have taken place in the region for nearly a month and a half (until end of February, time when this abstract was written). The closest station to the source area -part of the GEOSCOPE network located in Coyhaique, about 80 km away from the epicenters- reveals seismic activity about 3 hours before the first event. Immediately after the first event, more than 20 events per hour were detected and recorded by this station, rate which decreased with time with the exception of those time intervals following larger events. More than six events with magnitude 5 or more have been recorded. Five seismic stations were installed surrounding the epicentral area between 27 - 29 January and are currently operational. After processing some of the recorded events, a sixth station was installed at the closest possible site of the source of the seismic activity. Preliminary analysis of the recorded seismic activity reveals a concentration of hypocenters - 5 to 10 km depth- along an eight-km NNE-SSW vertical plane crossing the Aysén fiord. Harmonic tremor has also been detected. This seismic activity is interpreted as the result of a magmatic process in progress which will most likely culminate in the generation of a new underwater volcanic edifice. Because the seismic activity fully extends across the Aysén fiord -the only maritime outlet of the cities of Coyhaique, Puerto Aysén and Puerto Chacabuco- and large fisheries plants exist in the area, we will continue monitoring the area with experts of the National Emergency Office, National Geology and Mines Service, and Millennium Nucleus on Seismic Hazards to mitigate any possible disaster.
DE: 8419 Volcano monitoring (7280)
SC: Union [U]
MN: 2007 Joint Assembly