The 2007 Bengkulu earthquakes were a series of
megathrust earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
s that struck the
Sunda Trench off the coast of
Sumatra
Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...
,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
, with three of magnitude 7 or greater. A series of
tsunami
A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...
bulletins was issued for the area. The most powerful of the series had a
magnitude of 8.4, which makes it in the top 20 of the
largest earthquakes ever recorded on a
seismograph.
Timeline
The first earthquake occurred at 11:10:26
UTC (18:10
local time) on 12 September 2007, and was an 8.4
earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
on the
moment magnitude scale
The moment magnitude scale (MMS; denoted explicitly with or Mwg, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. was defined in a 1979 paper ...
.
It had a focal depth of 34 km, at , about 130 km southwest of
Bengkulu on the southwest coast of
Sumatra
Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...
,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
, and some 600 km west-northwest of Indonesia's capital city,
Jakarta
Jakarta (; , Betawi language, Betawi: ''Jakartè''), officially the Special Capital Region of Jakarta (; ''DKI Jakarta'') and formerly known as Batavia, Dutch East Indies, Batavia until 1949, is the capital and largest city of Indonesia and ...
. It was followed by several earthquakes of magnitude 5 through 6 along the same fault, west of Sumatra.
The second largest earthquake, 7.9
Mw,
occurred later the same day at 23:49:04
UTC (06:49:04 local time the following day). It was centred about 35 km underground, at , some south-southeast of
Padang, Indonesia and about 205 km northwest of Bengkulu (about 225 km northwest of the magnitude 8.4 earthquake).
After further aftershocks above magnitude 5, a third large earthquake, 7.0
Mw, occurred at 03:35:28 UTC (10:35:28 local time) on 13 September.
[ It was centred about 10 km underground, at , some 165 km south-southwest of Padang and 345 km west-northwest of Bengkulu. It is regarded as an aftershock of the two larger earthquakes.]
Aftershocks continued into 13 September and 14 September, with more earthquakes ranging up to magnitude 6.4. Most of the aftershocks have been northwest of the original magnitude 8.4 earthquake. A 6.7 struck Southern Sumatra on Sept 20, 2007.
Tidal buoys positioned in the Indian Ocean and other seismic tools have led scientists to issue a series of tsunami bulletins.
Effects
The tremors of the 8.4 earthquake lasted for several minutes. It caused buildings to sway in Jakarta, and some buildings were reported to have collapsed in the city of Bengkulu, Bengkulu Province, about 100 km (62 mi) from the epicenter. Tremors felt in Jakarta were described as being "violent". It was reported that several high-rise buildings were evacuated.[Powerful quake shakes Indonesia](_blank)
BBC News
BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broad ...
The earthquake also led to a power outage in Bengkulu, which crippled communications. The death toll of the earthquakes is 25 with 161 people injured.
Tremors were felt in neighbouring countries as far away as Southern Thailand. In Singapore
Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...
, which is about 670 km (416.3 mi) from the epicenter, the tremor was felt at around 11:10 UTC (19:10 local time). Most of the Central and Eastern part of Singapore
Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...
had felt the tremor. In Peninsular Malaysia
Peninsular Malaysia, historically known as Malaya and also known as West Malaysia or the Malaysian Peninsula, is the western part of Malaysia that comprises the southern part of the Malay Peninsula on Mainland Southeast Asia and the list of isla ...
, tremors were reported after 19:15 local time, including Kuala Lumpur
Kuala Lumpur (KL), officially the Federal Territory of Kuala Lumpur, is the capital city and a Federal Territories of Malaysia, federal territory of Malaysia. It is the largest city in the country, covering an area of with a census population ...
, Putrajaya
Putrajaya (), officially the Federal Territory of Putrajaya (), is the administrative centre of Malaysia. The Seat of government, seat of the Government of Malaysia, federal government of Malaysia was moved in 1999 from Kuala Lumpur to Putrajay ...
, Johor Bahru
Johor Bahru, abbreviated as JB, is the capital city of the Malaysian state of Johor. It is the core city of Johor Bahru District, Malaysia's second-largest district by population and the second-largest district economy. Covering an area of ...
, Malacca and Penang. Like Singapore, the tremors were most severe on high-rises, resulting in minor panic and evacuations. No casualties were reported in the country, as of 13 September.
Tsunami
Sea level readings indicated that a tsunami
A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...
was generated. A total of 4 tsunami alerts were issued in 24 hours. After the first, and largest, earthquake, the Pacific Tsunami Warning Centre issued a tsunami alert for much of the Indian Ocean basin. A tsunami approximately 1 metre high was reported at Padang, Indonesia. A 1.5 metre tsunami was observed in Sikakap beach on South Pagai Island. A small tsunami, some 15 cm high, was reported at the Cocos Islands. Sumatra was taken off tsunami alert after two hours. A weak tsunami caused some damage in Serangai, located north of Bengkulu. The tsunami had a flow depth of and maximum run-up of , measured on a cliff top.
Tsunami warnings were also issued in India and other countries around the Indian Ocean soon after the earthquake. The Government of India
The Government of India (ISO 15919, ISO: Bhārata Sarakāra, legally the Union Government or Union of India or the Central Government) is the national authority of the Republic of India, located in South Asia, consisting of States and union t ...
asked the states of Tamil Nadu
Tamil Nadu (; , TN) is the southernmost States and union territories of India, state of India. The List of states and union territories of India by area, tenth largest Indian state by area and the List of states and union territories of Indi ...
, Kerala
Kerala ( , ) is a States and union territories of India, state on the Malabar Coast of India. It was formed on 1 November 1956, following the passage of the States Reorganisation Act, by combining Malayalam-speaking regions of the erstwhile ...
, Andhra Pradesh
Andhra Pradesh (ISO 15919, ISO: , , AP) is a States and union territories of India, state on the East Coast of India, east coast of southern India. It is the List of states and union territories of India by area, seventh-largest state and th ...
and the union territories of Andaman and Nicobar Islands
The Andaman and Nicobar Islands is a union territory of India comprising 572 islands, of which only 38 are inhabited. The islands are grouped into two main clusters: the northern Andaman Islands and the southern Nicobar Islands, separated by a ...
and Puducherry to be on high alert. By late 12 September, the tsunami warning was recalled. Similarly, a tsunami alert was issued in Peninsular Malaysia
Peninsular Malaysia, historically known as Malaya and also known as West Malaysia or the Malaysian Peninsula, is the western part of Malaysia that comprises the southern part of the Malay Peninsula on Mainland Southeast Asia and the list of isla ...
at 20:50 ( local time) for the coastal areas of Perlis
Perlis (Kedah Malay language, Kedah Malay (Perlis dialect): ''Peghelih'') is a Negeri, state of Malaysia in the northwestern coast of Peninsular Malaysia. It is the smallest state in Malaysia by area and population. The state borders the Thai ...
, Kedah
Kedah (), also known by its honorific Darul Aman (Islam), Aman (دار الأمان; Arabic for 'The Safe Abode') and historically as Queda, is a States and federal territories of Malaysia, state of Malaysia, located in the northwestern part of ...
, Perak
Perak (; Perak Malay: ''Peghok'') is a States and federal territories of Malaysia, state of Malaysia on the west coast of the Malay Peninsula. Perak has land borders with the Malaysian states of Kedah to the north, Penang to the northwest, Kel ...
and Penang; the alert was lifted two hours later. However, Malaysian authorities had detected a high tsunami heading away from the epicenter of the earthquake.
Tectonic summary
According to the US Geological Survey, the earthquake was caused by thrust faulting on the boundary between the Australian Plate and the Sunda Plate which ruptured a 250 × 170 km section of the subduction interface. At the location of the earthquake, offshore of the west coast of Sumatra, the Australia plate moves northeast with respect to the Sunda Plate at a velocity
Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...
of about 69 mm/year, oblique to the orientation of the plate boundary. The component of plate motion perpendicular to the boundary produces thrust faulting on the offshore plate-boundary.
The magnitude 7.9 earthquake was also a result of thrust faulting on the same plate boundary. It occurred about 225 km northwest of the magnitude 8.4 earthquake, at the northern end of the aftershock zone. This event ruptured 2 different patches of the interface, each separated by a distance of 120 km and around 50 × 40 km in size or less.[
The magnitude 8.4 earthquake was the most powerful earthquake of 2007 to date, more powerful than the two March 2007 Sumatra earthquakes nearby and the 2007 Peru earthquake. It was the second most powerful earthquake since the magnitude 9.3 ]2004 Indian Ocean earthquake
On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea ...
, exceeded only by the magnitude 8.6 2005 Nias–Simeulue earthquake. The two largest earthquakes were the fourth and fifth earthquakes with magnitude 7.9 or greater to have occurred on or near the plate boundaries offshore of western Sumatra in 7 years, the others being the magnitude 7.9 earthquake of 4 June 2000; the magnitude 9.3 2004 Indian Ocean earthquake
On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea ...
on 26 December 2004; and the magnitude 8.6 Nias–Simeulue earthquake on 28 March 2005.
According to data from the Japanese PALSAR microwave
Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
sensor aboard the Daichi(ALOS) satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
, South Pagai Island was uplifted, creating 6 new islands, and exposing previously submerged coral reefs
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
...
as well as enlarging existing islands.[Southern Sumatra Earthquake in 2007, coastal change, GSI]
See also
* List of earthquakes in 2007
* List of earthquakes in Indonesia
* March 2007 Sumatra earthquakes
References
Further reading
*
*
*
External links
USGS Earthquake Center 8.5 tracking report
USGS Earthquake Center 7.9 tracking report
NOAA/NWS/West Coast and Alaska Tsunami Warning Center
Tsunami bulletin number 003
Pacific Tsunami Warning Center/NOAA
The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...
/ NWS
Observations on the Southern Sumatra Earthquakes of September 12–13, 2007
– Earthquake Engineering Research Institute
{{DEFAULTSORT:Sumatra Earthquakes, September 2007
2007 earthquakes
2007–09 Sumatra earthquakes
2007 disasters in Indonesia
September 2007 in Indonesia
Earthquake clusters, swarms, and sequences
Bengkulu