Sunday, 19 August 2012

Earthquake hits Sulawesi.

On Saturday 18 August 2012, slightly after 5.40 pm, local time (slightly after 9.40 am GMT), the Indonesian island of Sulawesi was hit by an Earthquake measured by the United States Geological Survey as 6.3 on the Richter Scale at a depth of 19.9 km, by the Indonesian agency Badan Meteorologi Klimatologi dan Geofisika as 6.2 on the Richter Scale at a depth of 10 km, and by Geoscience Australia as 6.5 on the Richter Scale at a depth of 35 km. Any of these measurements represents a serious Earthquake, and there are mixed reports coming from the scene. The area reportedly suffered 15 minutes of 'intense shaking', and there has apparently been considerable localized damage to property and a number of injuries and possibly fatalities; some reports claiming a six-year-old child has been killed by a collapsing house, and others stating the child was only injured but that a family of four was killed by a flash flood.

Map showing the area affected by the quake, which would have been felt within the black circle, and caused damage within the red circle. Geoscience Australia.

The tectonic situation beneath Sulawesi is complex, as it is caught in the collisional zone between the Eurasian, Pacific and Australian Plates. The north of the island is located on a breakaway section of the Eurasian Plate, called the Sangihe Plate. To the east lies the remnant Molucca Sea Plate, which is being subducted beneath both the Sangihe Plate and the more easterly Halmahera Plate, leading to Earthquakes and volcanism on Sulawesi and the islands of the Sangihe Ard in the west and the islands of the Halmahera Arc in the east.

The subduction of the Molucca Sea Plate beneath the Sangihe and Halmahera Plates. What on Earth.

The south of the island mostly lies on the Banda Sea Plate, which is being subducted beneath the Timor  Plate to the south, leading to further Earthquakes, as well as volcanism in the Timor Arc. The southwesternmost tip of Sulawesi lies on the Sunda Plate, with a complex system of convergent and transform faults bisecting the South Sulawesi Peninsula.

See also Eruption on Mount SirungEruptions on Batu TaraEruptions from the Tompaluan Crater, Lokon-Empung, SulawesiVolcanic activity in the Halmahera Islands and Earthquakes on Sciency Thoughts YouTube.

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