Solomon Islands

Solomon Islands: M7.0 Santa Cruz Islands Earthquake of 18 July 2015

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Tectonic Summary

The July 18, 2015 M 7.0 earthquake northwest of Lata, in the Solomon Islands, occurred as the result of normal faulting, on either an east-west striking structure dipping moderately to the north, or on a southeast-northwest striking structure dipping more steeply towards the southwest. At the latitude of this earthquake, the Australia plate moves towards the east-northeast at a rate of 95 mm/yr with respect to the Pacific plate. The location and mechanism of this event are consistent with its occurrence within the oceanic crust of the Pacific plate, 500 km to the northeast of the major local plate boundary between the Australia and Pacific plates, and directly above the northern edge of the Australia slab that subducts from the North New Hebrides Trench to the east beneath the Santa Cruz Islands.

The Australia:Pacific plate boundary system from the Solomon Islands towards Vanuatu is one of the most seismically active regions of the planet, and frequently hosts major earthquakes. 18 other M7+ events have occurred within 250 km of the July 18, 2015 earthquake over the preceding century. The July 2015 earthquake is located at the northern end of the earthquake sequence associated with the February 6th, 2013 M8.0 earthquake, which struck 45 km to the south of the July 18, 2015 event. The 2013 event caused several fatalities, injuries and significant damage on local islands, mostly associated with the tsunami spawned by the earthquake.