The United States Geological Survey recorded a Magnitude 6.4 Earthquake at a depth of 169.2 km roughly 2 km southwest of Tafea Island, Vanuatu, slightly after 8.45 pm local time (slightly after 9.45 am GMT) on Friday 13 July 2018. There are no reports of any damage or casualties associated with this event, though people reported feeling it on Shefa and Tanna islands. This is roughly what would be expected with such a deep Earthquake, with the event being felt over a wide area, but little or no damage, as the energy of the quake is dissipated over a wide area before it reaches the surface.
The approximate location of the 13 July 2018 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, fueling 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.
Follow Sciency Thoughts on Facebook.