Source processes of the 2009 Irian Jaya, Indonesia, earthquake doublet

On January 3, 2009 UT, an earthquake doublet with moment magnitudes of 7.6 and 7.4 occurred along the New Guinea trench near the northern coast of Irian Jaya, Indonesia. The events were separated by three hours in time and 60 km in space, having similar thrust faulting mechanisms. The Solomon and New Britain Islands regions located east of the source area are well known for the occurrence of earthquake doublets due to the complex tectonic settings. To investigate the source processes of the earthquake doublet, we have performed teleseismic waveform inversions using P-wave displacement records from the IRIS-DMC database. The results of the inversions are consistent with the direction of the subduction along the New Guinea trench for both of the earthquakes. Significant slips exceeding 5.0 m appear near the hypocenters, and the slip distributions look to be complementary to each other. The rupture starting point of the second event is close to the edge of the slip distribution of the first event. Our source models support the triggering mechanism of doublet events suggested by Lay and Kanamori (1980). The results also suggest the state of stress in the Irian Jaya region and the mechanism of earthquakes in this subduction zone.