September 2007 Sumatra earthquakes

The Sumatra earthquake of September 2007, there were a series of earthquakes in the Sunda Trench off the coast of Sumatra, Indonesia, of which three had a magnitude that was greater than Mw = 7.0. A series of tsunami warnings were issued for the sea area. Through the series of earthquakes at least 25 people were killed, 161 injured, some seriously.

Series of earthquakes

The first earthquake occurred on 12 September 2007 at 11:10:26 UTC clock ( 18:10:26 local time clock ) and reached the strength of Mw = 8.5 on the moment magnitude scale. The hypocenter of the earthquake was 34 km depth about 130 km southwest of Bengkulu on the southwest coast of the Indonesian island of Sumatra, more than 600 km west- northwest of the capital, Jakarta. The quake was followed by several aftershocks along the same fault west of Sumatra, which reached a magnitude 5-6.

The second largest earthquake with the magnitude Mw = 7.9 occurred a few hours later to clock 23:49:04 UTC ( 06:49:04 local time on the following day ). Its hypocenter was about 10 km below the earth's surface, at 2 ° 30 ' 22 " S, 100 ° 54' 22" E - 2.506100.906, about 185 km south- southeast of Padang, and 205 km north-west of Bengkulu, which is about 225 km northwest of the first strong earthquake.

After another aftershock with a magnitude greater than five to ( 10:35:26 local time clock ) another strong quake = 7.0 occurred on 13th September at 03:35:26 UTC clock with the value of Mw. Its center was 2 ° 9 ' 36 "S, 99 ° 51 ' 4" O- 2.1699.851, about 165 km south- south-west of Padang and 345 km west- northwest of Bengkulu, about 10 km below the surface.

The aftershocks continued into the 13th and 14th September and some of which reached a magnitude value Mw = 6.4. Most aftershocks were northwest of the original first very strong earthquake.

In the Indian Ocean distributed measurement buoys and other seismic instruments prompted the scientists to issue warnings of a tsunami.

Effects

The tremors of the 8.5 Mw earthquake lasted for several minutes. This swayed buildings in Jakarta and it was reported that away Located in the city of Bengkulu, about 130 km from the epicenter, several buildings collapsed. Eyewitnesses in Jakarta described the tremors as "massive ". Several skyscrapers were evacuated.

The tremors were also felt in surrounding states, for example in southern Thailand and Singapore, which lies about 670 km from the epicenter. On the Malay Peninsula, the shocks after 19:15 local time clock were noted, among other things, in Kuala Lumpur, Putrajaya, Johor Bahru, Malacca and Penang. As in Singapore and Jakarta, the tremors were felt in most high-rise buildings, leading to panic and evacuations after themselves.

Tsunami

Observations of sea level showed that a tsunami was triggered by the quake. A total of four tsunami warnings were announced within 24 hours. After the first, the largest earthquake that Pacific Tsunami Warning Centre had issued a tsunami warning for the largest part of the Indian ocean. A tsunami, which was about a meter high, was observed in Padang. A small tsunami with a height of about 15 cm was recorded on the Cocos Islands. After two hours, the tsunami warning in Sumatra has been revoked.

Tsunami warnings were triggered by the earthquake in India and other countries around the Indian Ocean. The Government of India had the states of Tamil Nadu, Kerala and Andhra Pradesh, and the Union Territories Andaman and Nicobar Islands and Puducherry asked to be extremely vigilant. In the late evening of September 12, the warnings have been lifted. Similarly, local time was 20:50 clock triggered on the Malay Peninsula for the coastal areas of Perlis, Kedah, Perak and Penang alarm; the alarm was canceled two hours later. The Malaysian authorities, however, had recorded a tsunami that reached between one and three meters in height.

Tectonic Summary

According to the U.S. Geological Survey, the earthquake was triggered by the thrust fault at the boundary between the Australian plate and the Sundaplatte. At the location of the earthquake off the western coast of Sumatra, the Australian plate moves relative to Sundaplatte at a speed of 69 mm / yr to the northeast, oblique to the orientation of the plate boundary. The Plattenwegung perpendicular to the plate boundary causes the thrust to the lying off the coast of plate.

Even the earthquake with a magnitude of Mw = 7.9 was a result of a thrust fault on the same plate boundary. There about 225 km north-west of the earthquake occurred with a magnitude of 8.5 on the northern end of a zone in which concentrated the aftershocks.

The earthquake with a magnitude of Mw = 8.5 was the hitherto strongest earthquake of 2007, more than the two Sumatran earthquake of March 2007 near and the earthquake in Peru in 2007. It was the second strongest quake since the earthquake in the Indian Ocean 2004, the magnitude Mw = 9.3 reached and surpassed during the period only from the earthquake off Sumatra in 2005 with the MagnitudeMw = 8.6. The two strongest aftershocks were the fourth and fifth earthquake that = 7.9 or more achieved during the last seven years at or near the plate boundary off the western coast of Sumatra, a magnitude Mw. The other earthquakes in this strength were on June 4, 2000 ( magnitude Mw = 7.9 ), then the tsunami of 26 December 2004 (magnitude Mw = 9.3 ) and the earthquake off Sumatra on 28 March 2005 ( magnitude Mw = 8.6 ).

The two earthquakes occurred at the end of the southern part of a zone that was pulled even with the severe earthquake in 1833 apart and extending to the south of the island Enggano in a northwesterly direction to the north of the island of Siberut. In the Indian Ocean Tsunami of 2004, a large part of the boundary region between the Indian plate and the Burma plate was affected, and shortly afterwards trembled on 28 March 2005, the Mw 0.6 earthquake -8, a segment of the connection between the Australian plate and the Sunda plate. A large part of the Sunda Trench between the Andaman and Eggano was rocked by a series of earthquakes in the subduction zone since the earthquake of 26 December 2004, which triggered the catastrophic tsunami.