The United States Geological Survey recorded a Magnitude 5.1 Earthquake at a depth of 10.0 km roughly 5 km south of Efate Island, Vanuatu, slightly after 6.30 pm local time (slightly after 7.30 am GMT) on Thursday 5 September 2019. There are no reports of any damage or casualties associated with this event, though people reported feeling it on Efate Island.
The approximate location of the 5 September 2019 Vanuatu Earthquake. USGS.
Vanuatu is located on the southwestern fringe of the Pacific Plate, close to its boundary with the Australian Plate, which is being subducted along the New Hebrides Trench, to the west of the islands. The subducting Australian Plate passes under the islands of Vanuatu as it sinks into the Earth, causing Earthquakes as the plates stick together then break apart as the pressure builds up. As the plate sinks further it is partially melted by the heat of the friction combined with that of the Earth's interior. Some of the melted material then rises through the overlying Pacific Plate, fuelling the volcanoes of Vanuatu.
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.
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