September 12, 2007 Earthquake: Sumatra, Indonesia

Felt Report

On September 12, 2007, at 11:10:26 UTC [6:10 pm local time in Indonesia] an earthquake occurred 130 km (80 miles) SW of Bengkulu, Sumatra, Indonesia and 625 km (390 miles) WNW of JAKARTA, Java, Indonesia at 5:10 AM MDT, Sep 12, 2007. Twenty-five people killed and at least 161 injured, 56,425 buildings damaged or destroyed and roads damaged in Bengkulu and Sumatera Barat. Power and telephone outages occurred. Felt (VI) at Bengkulu; (V) at Padang; (IV) at Lampung, Palembang, Pekanbaru and Sibolga; (III) at Jambi; (II) at Banten and

Serang. Also felt at Medan. Felt (IV) at Duri and (III) at Jakarta, Java. Also felt at Bekasi and Kuningan. Felt (III) at Kuala Lumpur and Petaling Jaya, Malaysia and in Singapore. Also felt at Batang

Berjuntai, Batu Pahat, Gelugor, Johor Bahru, Kertih, Kuala Selangor, Muar, Penang, Pontian Kecil, Putrajaya, Sekudai and Subang Jaya, Malaysia and by people in high-rise buildings at Bangkok, Thailand and Male, Maldives. A seiche was observed in Khlong Saensaep in Bangkok, Thailand and sink holes which may

have been caused by the earthquake appeared at 3 locations in Ipoh, Malaysia. A tsunami was generated which caused some building damage (included above) in the Serangai area, north of Bengkulu.

Tectonic Summary

The southern Sumatra earthquake of September 12, 2007 occurred as the result of thrust faulting on the boundary between the Australian plate and the Sunda plate. At the location of the earthquake, the Australia plate moves northeast with respect to the Sunda plate at a velocity of about 69 mm/year. The direction of relative plate motion is oblique to the orientation of the plate boundary offshore of the west coast of Sumatra. The component of plate-motion perpendicular to the boundary is accommodated by thrust faulting on the offshore plate-boundary. Much of the component of plate motion parallel to the plate boundary is accommodated by strike-skip faulting on the Sumatra fault, which is inland on Sumatra proper.

The earthquake of September 12, 2007 is the fourth earthquake of magnitude greater than 7.8 to have occurred in the past decade on or near the plate boundaries offshore of western Sumatra. The September 12, 2007 earthquake occurred just north of the source region of the magnitude 7.8 earthquake on June 4, 2000, which killed approximately 100 people. The great magnitude 9.1 earthquake of December 26, 2004, which produced the devastating Indian Ocean tsunami of that date, ruptured much of the boundary separating the India plate and the Burma plate. Immediately to the south of the great 2004 earthquake, the magnitude 8.6 Nias Island earthquake of March 28, 2005, ruptured a segment of the plate boundary separating the Australia and Sunda plates.

(above from reference #1053)