Thursday 4 May 2017

Magnitude 6.9 Earthquake off the south coast of Mindanao Island, Philippines.

The United States Geological Survey recorded a Magnitude 6.9 Earthquake at a depth of 26 km about 26 km off the coast of Sarangani Province on southern Mindanao Island, Philippines, slightly after 4.20 am local time on Saturday 29 April 2017 (slightly after 8.20 pm on Friday 28 April GMT). There are no reports of any casualties directly associated with this event, however three people were reportedly injured following evacuations of coastal areas due to concerns about a tsunami triggered by this event. The quake also caused damage to a number of civic buildings, and at least one house collapse, as well as a temporary power outage. People have reported feeling this event across much of Mindanao, as well as on the northern tip of Sulawesi in Indonesia.

Workers clearing debris in General Santos in South Cotobato Province, following the 29 April 2017 Earthquake. Reuters.

The geology of the central Philippines is Complex. The west of Mindanao Island is located on the Banda (or Sunda) Microplate, and the east on the Philippine Plate, which is being subducted beneath the Sunda (or Banda) Microplate along the central part of the island. Immediately to the east of the Island the Pacific Plate is being subducted along the Philippine Trench, and passes beneath eastern Mindanao as it sinks into the Earth. This is not a smooth process, an the plates constantly stick together then break apart again as the pressure builds up, resulting in Earthquakes.

 Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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 23 April 2017 Mindanao Earthquake. USGS.

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