Friday 3 February 2012

Series of Earthquakes shakes Vanuatu.

On 3 February 2012 at approximately 0.35 am local time (1.35 pm on 2 February, GMT) the island nation of Vanuatu was shaken by an Earthquake with a magnitude of 7.1 on the Richter Scale, which occurred about 115 km west of the capital, Port Vila, at a depth of 23.1 km, according to the United States Geological Survey. There have been twenty-one significant aftershocks since the initial quake, the largest of which was recorded as measuring 5.7 on the Richter Scale by the GeoNet geological hazard monitoring system in New Zealand. There are no reports of any casualties or serious damage, and no tsunami warning has been issued, but the quake was reportedly felt on several of Vanuatu's islands.

Map showing the location of the quakes. Larger squares represent larger quakes. Blue squares are more recent than yellow squares. The red line is the Vanuatu Trench. From the United States Geological Survey.

Vanuatu is a nation used to Earthquakes; on average quakes exceeding 7.0 on the Richter Scale happen three times a year. It is comprised of a string of volcanic islands situated along the margin of the Pacific and Australian Plates. The Australian Plate to the west is being subducted beneath the Pacific Plate to the east along the Vanuatu Trench. The majority of the islands are located to the east of the trench, on the tops of submerged volcanoes; the volcanoes forming where material from the Australian Plate that has been melted by the heat of the Earth's interior rises up through the overlying Pacific Plate. In addition the Australian Plate is moving northward relative to the Pacific Plate. The movement of the Australian Plate under the Pacific Plate creates a great deal of friction, which is felt as Earthquakes.

The islands have over twenty volcanoes, six of which are currently active, and one (Yasur) is currently erupting, according to the Vanuatu Geohazards Observatory. None of these is considered an immediate threat, though in the past few thousand years the Islands have suffered a number of devastating caldera explosions.

A crater explosion on Mount Manaro on Ambae Island in 2005. BBC.