Triggering of earthquakes during the 2000 Papua New Guinea earthquake sequence

A sequence of large earthquakes occurred in the New Britain/New Ireland region of Papua New Guinea in late 2000. The sequence started with a M_w 6.8 earthquake along the New Britain Trench on 29 October. About 20 days later a M_w 8.2 earthquake occurred in the New Ireland region on 16 November and produced large strike-slip surface displacements and tsunamis. Following the M_w 8.2 event, two large earthquakes (M_w ∼ 7.5) occurred along the nearby New Britain Trench on 16 and 17 November. Furthermore, small triggered events were observed over a wide area outside of the rupture zones of the large earthquakes, with different focal mechanisms from those of the major events. There is likely some mechanism(s) that triggered this remarkable sequence, and we document the details of the spatial and temporal patterns of the events. We investigated if static stress changes can explain the initiation of the large earthquakes and also some groups of triggered smaller events. There are mixed results. The occurrences of the two M ∼ 7.5 major events may be explained by the static stress changes; however, there are also some earthquakes that are not consistent with triggering by static stress changes. There may be multiple mechanisms, including static and dynamic stress changes, that are needed to explain the complicated sequence of earthquakes.