Historical Seismicity and Seismotectonic Context of the Great 1979 Yapen and 1996 Biak, Irian Jaya Earthquakes

We present relocations of over 220 historical and recent earthquakes in the northwestern part of Irian Jaya, in the context of the large earthquakes of 1979 and 1996. Our results document continuous activity on a 420-kmsegm ent of the Sorong Fault, with a possible extension over an additional 330 kmto the west. We also show that some level of activity did take place on the New Guinea Trench prior to the 1996 Biak earthquake, and relocate a large (MPAS=7.4) event on 02 April 1947 to the trench, at 138°E. We speculate that the large earthquake of 26 May 1914 may also have taken place on the New Guinea Trench. We study the pattern of activity following the 1979 Yapen earthquake, which triggered stress release in the Pandaidori Islands, also the location of stress transfer following the 1996 Biak earthquake.