The United States Geological Survey recorded a Magnitude 5.9 Earthquake at a depth of 20.3km, beneath the northern part of Posi Posi Rao Island in the North Maluku Province of Indonesia, slightly slightly after 1.05 am local time on Sunday 19 November 2017 (slightly after 4.05 pm on Saturday 18 November, GMT). There are no reports of any casualties associated with this event, but it did cause some minor damage to buildings in Posiposi village, on the south part of the island.
Damage to buildings on Posiposi Rao Island following the 19 Novenmber 2017 Earthquake. Earthquake Report.
Posiposi Rao lies at the northern end of the Halmahera Islands chain, a volcanic arc formed where one tectonic plate is being subducted beneath another, with the underlying plate being melted by the heat of the Earth's interior, and lighter minerals bubbling up through the overlying plate to form volcanoes. However the Halmahera Islands are unusual in that they lie on a double subduction zone. The underlying plate, a northeaster extension of the Molucca Sea Plate, is being overridden form the Philippine Plate from the east and the Eurasian Plate from the west. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.
Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right. Hall & Wilson (2000).
Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
The approximate location of the 19 November 2017 Posiposi Rao Earthquake. USGS.
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