December 8, 2016 Earthquake: Solomon Islands

Felt (VIII) at Kirakira, (VI) at Honiara and (III) at Gizo. Also felt at Brisbane, Australia. Kirakira, Makira and Ulawa, Solomon Islands - CDI: 8; Honiara, Guadalcanal, Solomon Islands - CDI: 6; Gizo, Western, Solomon Islands - CDI: 3; Brisbane, Queensland, Australia - CDI: 2

The Dec 8, 2016, M 7.8 Solomon Islands earthquake occurred as the result of shallow, slightly oblique reverse faulting on or near the plate boundary between the Australia and Pacific plates. Focal mechanism solutions indicate that rupture occurred on either a northwest or north-south-striking, moderately dipping reverse fault. At the location of the earthquake, the Australia plate subducts beneath the Pacific plate towards the east-northeast at a velocity of about 96 mm/yr. The location, depth, and focal mechanism solutions of the Dec 8th earthquake are consistent with its relation to under-thrusting of the Australia plate beneath the Pacific plate (the northwest-striking plane of the focal mechanism solution).

The Dec 8th earthquake occurred about 100 km northwest of where the Australia:Pacific plate boundary transitions from thrust to transform tectonics between the New Britain Trench to the northwest and the New Hebrides Trench farther east. A pair of large earthquakes (M 7.6 and M 7.4) occurred in that plate boundary transition region in April 2014. More broadly, the Solomon Islands Arc is very seismically active, with 53 earthquakes of M 6.5+ occurring within 250 km of the Dec 8th event over the preceding century. The largest of these was a M 7.9 earthquake about 50 km to the southwest in Oct 1931, near the New Britain Trench. In 1979, a M 7.1 earthquake occurred in an almost identical location (8 km northwest) to the Dec 8, 2016 event. None of these historic earthquakes are known to have caused shaking-related fatalities, likely because of their remote location far from population centers that might be vulnerable to earthquake shaking. (ref #13456)

The earthquake caused damage to buildings in Kirakira including homes, a hospital, a church, the World Vision office and cut off the town's power supply. Early reports from the National Emergency Operations Centre report that over 3000 people in the provinces of Makira, Malaita and Temotu have been affected by the earthquake, with many homes destroyed. (ref #11698)

There are reports of collapsed buildings and landslides it the most affected Makira-Ulawa province. The police said 35 to 40 houses on the island of Makira were damaged, including the police barracks at the provincial capital Kirakira. Most buildings were reportedly traditional-style houses…The quake caused widespread blackouts, knocked out phone systems and even caused the tsunami warning system to go down... School office buildings, a classroom and staff housing of Marou Bay Primary School in West Makira were severely damaged, RadioNz reported. This region has also been affected by several landslides. Destruction was reported in other villages in the Marou Bay area. Pawa Secondary School on Ugi Island has also been damaged. One teacher said a staff house and students' sanitation block have been flattened. (ref #11703)

only one reported casualty, a 25-year-old with non-specific injuries. The remoteness of the region and the failure of communications meant it was impossible to know the full extent of any injuries or damage (ref #11702)

About 7000 people across three provinces are reported to have been affected by the recent earthquakes in the Solomon Islands. Disaster authorities said around 200 buildings had been destroyed or damaged in the provinces of Makira & Ulawa, Malaita and Guadalcanal. Among them were 11 schools and a medical clinic (ref #11705)

An 11-year old girl is the first confirmed fatality from the massive earthquakes which hit Solomon Islands last week. The girl died when a building collapsed on top of her on Guadalcanal (ref #11714)