April 13, 2014 Earthquake: Solomon Islands

Tectonic Summary

The April 13, 2014 M 7.4 Solomon Islands earthquake occurred as the result of nearly pure reverse faulting on an approximately east-west oriented structure near the oceanic trench that marks the plate boundary between the Australia and Pacific plates. At the location of the earthquake, the Australia Plate converges with and slips past the Pacific plate at a rate of 95 mm/yr. The April 13 earthquake occurred along a portion of this plate boundary that transitions from thrust to transform tectonics between the New Britain Trench to the northwest and the New Hebrides Trench farther east. The earthquake occurred about 110 km SSE of Kirakira, Solomon Islands.

The April 13 earthquake occurred less than 24 hours and approximately 20 km to the southwest of a M 7.7 strike-slip earthquake on April 12, 2014. While the April 12 strike-slip earthquake likely represented Australia:Pacific plate boundary faulting, the April 13 earthquake is located south of the plate boundary at a depth of approximately 35 km, and as such may represent tearing of the Australia plate to accommodate the abrupt change in Australian plate interaction with the Pacific plate (subduction to the north and west; left-lateral translation to the east).

The region of the April 12 earthquake is very seismically active, with 28 earthquakes of M6+ occurring within 100 km and 62 events of M7+ within 500 km since 1900. The majority of these earthquakes are grouped to the northwest around the Solomon Islands and to the east near Vanuatu and the Santa Cruz Islands. Notable earthquake within 100 km include a doublet of M7.0 events in November 1978, events of M7.1 in 1931 and 1937, and an M7.2 in 1910. The most recent local event prior to the April 12 earthquake was an M6.0 on April 4, 2014 94 km to the NW. The April 12 earthquake also occurred about 950 km to the SE of an earthquake sequence south of Bougainville Island, Papua New Guinea that began with an M6.1 on April 11, 2014. On February 6, 2013, an M8.0 struck offshore of the Santa Cruz Islands about 340 km east of the April 12 event. The 2013 earthquake triggered a regional tsunami of about 1.5 m and was followed by aftershocks of M7.0 and two of M7.1...

(above from reference #13456)