Tectonic interpretation of aftershock relocations in eastern Papua New Guinea using teleseismic data and the arrival pattern method

The arrival pattern (AP) method and teleseismic data have been used to relocate aftershocks following three major (M_w >= 7.8) interplate earthquakes that occurred in eastern Papua New Guinea in 2000 November. The first event was an M_w= 8.0 strike-slip earthquake that ruptured the Weitin fault over a length of ~100 km. No aftershocks were located in the upper 15 km, suggesting that the accumulated strain was fully released in this event. The two subsequent M_w= 7.8 thrust events occurred on the New Britain trench. Wadati-Benioff zones dipping ~20° define the locations of the thrust events at 152°E and 153°E on fault planes with strikes of 75° and 65°, respectively. The plot of aftershocks defines a complex seismic zone beneath New Ireland where events have occurred in the overriding Pacific and South Bismarck plates above the deeper zone of subduction of the Solomon Sea Plate. These events cluster in a broad zone to the northeast of the Weitin fault rather than defining a linear feature that might have been expected following a near-vertical major strike-slip event.