Mass movement-induced tsunamis: main effects during the Patagonian Fjordland seismic crisis in Aisén (45°25'S), Chile

Abstract

The epicentre of the long-lasting seismic crisis started on the evening of January 22,2007 and it was located 20 km to the west of Puerto Chacabuco in the Patagonian fjordland, Chile (45°25'S). Approximately 7,000 events were recorded up to early May, four of which reached magnitudes greater than 5 (Richter), with local intensities up to VII in Puerto Chacabuco and Puerto Aisén and VI in Coihaique. The seismic swarm was located within the Liquiñe-Ofqui Fault Zone (LOFZ), which controls the emplacement of several monogenetic volcanic cones and larger stratovolcanoes. The January 23 (Ms 5,2) and April 1 (Ms 5,4) events caused minor damages in salmón industry installations near the epicentral zone, however the earthquake that oceurred at 13:54 hours (local time) on April 21 (Mw 6,2) triggered various mass movements on the Fiordo Aisén slopes and generated tsunamis. Debris flows and tsunami waves caused the death of three people and the disappearance of seven, in addition to severe damages to the salmón industry installations. A similar phenomenon had oceurred in 1927, but then fewer people inhabited the área. Initially, confusión dominated the scientific coordination of the emergeney management due to seismic data misinterpretation.