October 2010 Sumatra earthquake and tsunami
Encyclopedia
The October 2010 Sumatra earthquake was a magnitude
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

 7.7 Mw
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

 earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

 that occurred on 25 October 2010 off the western coast of Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...

, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 at 21:42 local time (14:42 UTC). The earthquake occurred on the same fault that produced the 2004 Indian Ocean earthquake
2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...

. It was widely felt across the provinces of Bengkulu
Bengkulu
Bengkulu is a province of Indonesia. It is on the southwest coast of the island of Sumatra, and borders the provinces of West Sumatra, Jambi, South Sumatra and Lampung. The capital and largest city is Bengkulu city. It was formerly the site of a British garrison, which they called Bencoolen...

 and West Sumatra
West Sumatra
West Sumatra is a province of Indonesia. It lies on the west coast of the island Sumatra. It borders the provinces of North Sumatra to the north, Riau and Jambi to the east, and Bengkulu to the southeast. It includes the Mentawai Islands off the coast...

 and resulted in a substantial localized tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 that struck the Mentawai Islands
Mentawai Islands
The Mentawai Islands are a chain of about seventy islands and islets off the western coast of Sumatra in Indonesia. Siberut is the largest of the islands. The other major islands are Sipura, North Pagai and South Pagai . The islands lie approximately 150 km off the Sumatran coast, across the...

.

Many villages on the islands were affected by the tsunami, which reached a height of 3 m (9 ft) and swept as far as 600 m (1800 ft) inland. The tsunami caused widespread destruction that displaced more than 20,000 people and affected about 4,000 households. 435 people were reported to have been killed, with over 100 more still missing. The subsequent relief effort was hampered by bad weather and the remoteness of the islands, which led to delays in the reporting of casualties.

Earthquake characteristics

The earthquake occurred around 150 miles (241.4 km) west of Bengkulu
Bengkulu
Bengkulu is a province of Indonesia. It is on the southwest coast of the island of Sumatra, and borders the provinces of West Sumatra, Jambi, South Sumatra and Lampung. The capital and largest city is Bengkulu city. It was formerly the site of a British garrison, which they called Bencoolen...

, close to the Mentawai Islands
Mentawai Islands
The Mentawai Islands are a chain of about seventy islands and islets off the western coast of Sumatra in Indonesia. Siberut is the largest of the islands. The other major islands are Sipura, North Pagai and South Pagai . The islands lie approximately 150 km off the Sumatran coast, across the...

, southwest of South Pagai
South Pagai
South Pagai is one of the Mentawai Islands off the west coast of Sumatra in Indonesia. It is south of North Pagai Island...

. The USGS first reported the hypocenter
Hypocenter
The hypocenter refers to the site of an earthquake or a nuclear explosion...

 of the quake at 20.5 miles (33 km) deep, but later changed it to 8.8 miles (14.2 km) deep and then 12.8 miles (20.6 km). The USGS also estimated the magnitude at 7.5 before revising the measurement to 7.7. The intensity was MM IV in Bengkulu and MM III in Padang
Padang, Indonesia
Padang is the capital and largest city of West Sumatra, Indonesia. It is located on the western coast of Sumatra at . It has an area of and a population of over 833,000 people at the 2010 Census.-History:...

.

The island of Sumatra lies above the Sunda megathrust
Sunda megathrust
The Sunda megathrust is a fault that extends approximately 5,500 km from Myanmar in the north, running along the southwestern side of Sumatra, to the south of Java and Bali before terminating near Australia...

, the interface between the subducting
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

 Australian Plate and the overriding Sunda Plate
Sunda Plate
The Sunda Plate is the tectonic plate on which the majority of Southeast Asia is located. It was formerly considered a part of the Eurasian Plate, but GPS measurements have confirmed its independent movement at 10 mm/yr eastward relative to Eurasia...

. Movement on this structure has been responsible for many large historical megathrust earthquake
Megathrust earthquake
Megathrust earthquakes occur at subduction zones at destructive plate boundaries , where one tectonic plate is forced under another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, these earthquakes are among the world's largest, with moment magnitudes ...

s. The most recent sequence of large ruptures started with the 2004 Indian Ocean earthquake
2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...

 and included the 2005 Sumatra earthquake
2005 Sumatra earthquake
The 2005 Sumatra earthquake, referred to as the Nias Earthquake by the scientific community, was a major earthquake on 28 March 2005, located off the west coast of northern Sumatra, Indonesia. Approximately 1300 people were killed by the earthquake, mostly on the island of Nias...

 and the 2007 Sumatra earthquakes. The October 2010 earthquake is thought to have been a result of thrust fault
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...

ing along or near the plate interface from the calculated focal mechanism
Focal mechanism
The focal mechanism of an earthquake describes the inelastic deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is also known as a fault-plane solution...

 and the focal depth
Hypocenter
The hypocenter refers to the site of an earthquake or a nuclear explosion...

. According to seismic hazard potentials and deformation features, the Sunda Trench can be divided into several segments. The southern segment lies to the south of Siberut Island. The rupture area of this earthquake is situated within the southern segment, where historical earthquakes include the earthquake of 1797
1797 Sumatra earthquake
The 1797 Sumatra earthquake was the first in a series of great earthquakes that ruptured part of the Sumatran segment of the Sunda megathrust. It caused a damaging tsunami that was particularly severe near Padang, where a 150-200 ton English ship was driven 1 km inland up the Arau...

 and the Mw ~ 9.0 1833 Sumatra earthquake
1833 Sumatra earthquake
The 1833 Sumatra earthquake occurred on November 25, 1833, about 22:00 local time, with an estimated magnitude in the range Mw= 8.8–9.2. It caused a large tsunami that flooded the southwestern coast of the island. There are no reliable records of the loss of life, with the casualties being...

.

Unlike in 2004, the tsunami caused by the October 2010 earthquake did not propagate westwards and other Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 nations were unaffected. It has been suggested that the tremor may have been a large aftershock of the much larger Sumatran earthquakes of September 2007. The earthquake occurred around seven hours after the eruption of Mount Merapi on the Indonesian island of Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...

. However, the two events are not thought to be linked.

Aftershocks

Several aftershocks have been recorded since the initial quake, the more significant of which are listed below.
  • 5.0 – October 25 15:21:12 UTC
  • 6.1 – October 25 19:37:30 UTC
  • 4.9 – October 25 22:10:03 UTC
  • 6.2 – October 25 22:59:53 UTC
  • 5.3 – October 26 10:51:25 UTC
  • 5.3 – October 26 11:33:21 UTC
  • 5.0 – October 26 19:40:41 UTC
  • 5.0 – October 26 23:09:47 UTC
  • 5.8 – October 26 23:45:38 UTC

Impact

The earthquake's worst effects were felt on the remote Mentawai Islands. On the island of South Pagai
South Pagai
South Pagai is one of the Mentawai Islands off the west coast of Sumatra in Indonesia. It is south of North Pagai Island...

, the tsunami that followed the earthquake reached a height of 3 m (9 ft) and swept as far as 600 m (1800 ft) inland. According to Indonesian officials, more than 20 villages were hit by the tsunami, displacing more than 20,000 people and affecting about 4,000 households. The coastal village of Betu Monga on South Pagai was reported to have been destroyed with many residents still missing. Many residents of the villages of Peurogat and Beleerakso were also reported to be missing. Eighty percent of the houses in the North Pagai village of Muntei Baru were reported damaged or destroyed.

According to a spokesperson for the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG), the quake was felt in several mainland towns, but no damage or deaths were reported. The Mentawai Islands may have acted as a barrier, shielding the Sumatran coast by absorbing the brunt of the tsunami. As of October 30, 2010, the confirmed death toll stands at 435, with 110 more unaccounted for. Many of the missing are believed to have been swept out to sea.

Relief teams were initially unable to reach the islands due to poor weather conditions and rough seas. The Indonesian military was mobilized and international aid organizations also began a relief effort. The first aid began to arrive on October 27, two days after the earthquake and tsunami.

Early warning system problems

The BMKG issued a tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 warning based on seismographic data. An alert was broadcast from radios and mosque loudspeakers on the mainland, prompting thousands to flee to higher ground. It was later cancelled, but officials said that a tsunami warning system
Tsunami warning system
A Tsunami warning system is used to detect tsunamis in advance and issue warnings to prevent loss of life and damage. It consists of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of coastal...

 installed following the 2004 Indian Ocean earthquake and tsunami had failed to function properly. According to Indonesian officials, two of the system's buoys out at sea had been vandalized and were inoperative. The claim of a breakdown was disputed by German officials who were working with the Indonesians to maintain and develop the system. Jörn Lauterjung, the head of the German-Indonesia Tsunami Early Warning Project, said that it had "worked very well", only one sensor had not been working and its failure had not harmed the system's operation. However, the epicentre of the earthquake was so close to the islands that a warning would probably have been too late in any case, as the tsunami only took about five to ten minutes to reach Pagai.

Response

Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

n President Susilo Bambang Yudhoyono
Susilo Bambang Yudhoyono
Susilo Bambang Yudhoyono AC , is an Indonesian politician and retired Army general officer who has been President of Indonesia since 2004....

 interrupted a state visit to Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 to head to the Mentawai Islands, which he toured on October 28. Boediono
Boediono
Boediono is the Vice President of Indonesia, after winning the 2009 presidential election together with incumbent President Susilo Bambang Yudhoyono.-Education:Boediono received his early education in primary school in Blitar, East Java...

, the Vice President of Indonesia, visited the disaster area by helicopter on October 27 and called for better coordination of the aid effort. He encouraged Indonesians to "be tough in facing disasters", saying that "we must be prepared for whatever happens, just as our ancestors were over thousands of years." Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n Prime Minister Julia Gillard
Julia Gillard
Julia Eileen Gillard is the 27th and current Prime Minister of Australia, in office since June 2010.Gillard was born in Barry, Vale of Glamorgan, Wales and migrated with her family to Adelaide, Australia in 1966, attending Mitcham Demonstration School and Unley High School. In 1982 Gillard moved...

 issued a statement of condolences, saying: "I deeply regret the loss of life and the damage caused, and, of course, our thoughts go out to the families and loved ones of the people affected". She told the Australian Parliament that "the Australian Government has offered assistance to the Government of Indonesia should this be needed." Canadian Foreign Affairs Minister Lawrence Cannon
Lawrence Cannon
Lawrence Cannon, PC is a Canadian politician from Quebec and Prime Minister Stephen Harper's former Quebec lieutenant. On October 30, 2008 he was sworn in as Minister of Foreign Affairs...

 released a statement saying, "Canada’s condolences to the people of Indonesia following the recent natural disasters that have struck the country. "Canada is deeply concerned for the people of Indonesia, as they deal with the impacts of the recent tsunami and volcanic eruption,” said Minister Cannon. “On behalf of all Canadians, I offer our deepest sympathy to the families and friends of those killed, and wish a quick recovery to the injured. Canada stands ready to provide support to the people of Indonesia if requested. We have received no reports to date of Canadian deaths or injuries due to these disasters. Canadian officials in Ottawa and at the Canadian Embassy in Jakarta continue to monitor the impact of the disasters and remain in close contact with Indonesian authorities. We invite Canadian citizens in the affected area, even if they have not been affected by these events, to call home and reassure their loved ones." Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 Foreign Affairs Minister Yang Jiechi said in a statement "I wish to extend... my solicitude and condolences to the people affected by the disaster." Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

i President Asif Ali Zardari
Asif Ali Zardari
Asif Ali Zardari is the 11th and current President of Pakistan and the Co-Chairman of the ruling Pakistan Peoples Party . He is also the widower of Benazir Bhutto, who served two nonconsecutive terms as Prime Minister....

 and Prime Minister Yousaf Raza Gillani
Yousaf Raza Gillani
Yousuf Raza Gilani is the current prime minister of Islamic Republic of Pakistan. He was nominated as Prime Minister by the PPP, with the support of its coalition partners, Pakistan Muslim League , Awami National Party, Jamiat Ulema-e-Islam and Muttahida Qaumi Movement, on 22 March 2008...

 both sent messages to the President of Indonesia expressing their condolences and sympathy. Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

 Foreign Affairs Secretary Alberto G. Romulo, who was in Hanoi
Hanoi
Hanoi , is the capital of Vietnam and the country's second largest city. Its population in 2009 was estimated at 2.6 million for urban districts, 6.5 million for the metropolitan jurisdiction. From 1010 until 1802, it was the most important political centre of Vietnam...

, Vietnam to attend the 17th ASEAN Summit, has directed his department to get ready to provide Indonesia with assistance. The Philippines Embassy in Jakarta said in a statement that "The [Philippines] Embassy …stands ready to provide assistance, if needed," adding all Filipinos in Indonesia
Filipinos in Indonesia
Filipinos in Indonesia were estimated to number 4,800 individuals as of 2001, according to the statistics of the Philippine government. Most are based in Jakarta, though there is also a community in Surabaya...

 are safe. Portuguese President
President of Portugal
Portugal has been a republic since 1910, and since that time the head of state has been the president, whose official title is President of the Portuguese Republic ....

 Cavaco Silva sent his Indonesian counterpart a letter of condolences. He expressed his and Portugal's support for the country in such troubling times. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese Prime Minister Naoto Kan
Naoto Kan
is a Japanese politician, and former Prime Minister of Japan. In June 2010, then-Finance Minister Kan was elected as the leader of the Democratic Party of Japan and designated Prime Minister by the Diet to succeed Yukio Hatoyama. On 26 August 2011, Kan announced his resignation...

 and Minister for Foreign Affairs Seiji Maehara
Seiji Maehara
is a Japanese politician who has been a member of the House of Representatives of Japan since 1993. He was the leader of the Democratic Party of Japan from 2005 to 2006, and later served as Minister of Land, Infrastructure, Transport and Tourism and Minister of Foreign Affairs under the cabinets...

 sent messages to President Susilo Bambang Yudhoyono and Indonesian Minister of Foreign Affairs Marty Natalegawa
Marty Natalegawa
Raden Mohammad Marty Muliana Natalegawa, more commonly known as Marty Natalegawa, is an Indonesian diplomat and the Minister of Foreign Affairs in the Second United Indonesia Cabinet...

 expressing their condolences and sympathy. United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 President Barack Obama
Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...

 said in a statement: "Michelle
Michelle Obama
Michelle LaVaughn Robinson Obama is the wife of the 44th and incumbent President of the United States, Barack Obama, and is the first African-American First Lady of the United States...

 and I are deeply saddened by the loss of life, injuries, and damage that have occurred as a result of the recent earthquake and tsunami in West Sumatra. At the same time, I am heartened and encouraged by the remarkable resiliency of the Indonesian people and the commitment of their Government to rapidly assist the victims. As a friend of Indonesia, the United States stands ready to help in any way. Meanwhile, our thoughts and prayers are with the Indonesian people and all those affected by this tragedy."

See also

  • March 2007 Sumatra earthquakes
    March 2007 Sumatra earthquakes
    The March 2007 Sumatra earthquakes were two earthquakes which hit near the northern end of Lake Singkarak in Sumatra, Indonesia, on March 6, 2007 within two hours of each other.-Earthquakes:...

  • September 2007 Sumatra earthquakes
    September 2007 Sumatra earthquakes
    The September 2007 Sumatra earthquakes were a series of megathrust earthquakes that struck the Java Trench off the coast of Sumatra, Indonesia, three greater than magnitude 7. A series of tsunami bulletins was issued for the area...

  • April 2010 Sumatra earthquake
    April 2010 Sumatra earthquake
    The April 2010 Sumatra earthquake was a 7.8 Mw earthquake that occurred on April 7, 2010, at 5:15 AM local time near Banyak Islands, off the island of Sumatra in Indonesia. A tsunami watch was issued according to the Pacific Tsunami Warning Center in Honolulu which was later canceled...

  • List of earthquakes in Indonesia
  • 2010 eruption of Mount Merapi

External links

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