Sismicidad de la zona de fracturas de Clarión y sus posibles implicaciones tectónicas

Abstract

A sequence of earthquakes (3.4 ~ Ms ~6.4) occurred from September 15th, 1984 to May 28th, 1986 near the eastern end of the Clarion fracture zone, 30 km to the NNE of Clarion Island in the Revillagigedo Archipelago. The seismic events were located by the ISC between 18.9°-20.4° Nand 115.1° -116.9°W. This sequence represents the largest seismic activity during the period 1900-1989 in a region believed to be aseismic. Fault plane solutions for the six larger events were studied using first arrivals. All solutions suggest norma/faulting with two possible fault planes, one oriented NE-SW with an small right lateral component and the other almost E-W and left lateral component. The first solution agrees with the trend ofthe epicenter distribution; however, it is difficult to reconcile with the morphology of the ocean floor since it is oblique to the general trend of the Clarion fracture zone. Several possible explanations of the seismic sequence are discussed.