The September 2007 Sumatra earthquakes were a series of

megathrust Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqua ...

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s that struck the

Sunda Trench The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian Plate. It is ...

off the coast of Sumatra,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, with three of magnitude 7 or greater. A series of

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) 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 other underwater exp ...

bulletins was issued for the area. The most powerful of the series had a magnitude of 8.5, which makes it in the top 20 of the largest earthquakes ever recorded on a

seismograph A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output ...

Timeline

The first earthquake occurred at 11:10:26 UTC (18:10

local time Local time is the time observed in a specific locality. There is no canonical definition. Originally it was mean solar time, but since the introduction of time zones it is generally the time as determined by the time zone in effect, with dayligh ...

) on 12 September 2007, and was an 8.5

on the

moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mw, 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. It was defined in a 1979 pap ...

. It had a focal depth of 34 km, at , about 130 km southwest of

Bengkulu Bengkulu is a province of Indonesia. It is located on the southwest coast of Sumatra. It was formed on 18 November 1968 by separating out the former Bencoolen Residency area from the province of South Sumatra under Law No. 9 of 1967 and was ...

on the southwest coast of Sumatra,

, and some 600 km west-northwest of Indonesia's capital city, Jakarta. It was followed by several earthquakes of magnitude 5 through 6 along the same fault, west of Sumatra. The second largest earthquake, 7.9 M_w, 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 Padang () is the capital and largest city of the Indonesian province of West Sumatra. With a Census population of 1,015,000 as of 2022, it is the 16th most populous city in Indonesia and the most populous city on the west coast of Sumatra. ...

and about 205 km northwest of Bengkulu (about 225 km northwest of the magnitude 8.5 earthquake). After further aftershocks above magnitude 5, a third large earthquake, 7.0 M_w, 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 8.5 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 Province Bengkulu is a province of Indonesia. It is located on the southwest coast of Sumatra. It was formed on 18 November 1968 by separating out the former Bencoolen Residency area from the province of South Sumatra under Law No. 9 of 1967 and was ...

, about 100 km from the

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

. Tremors felt in Jakarta were described as being "violent". It was reported that several high-rise buildings were evacuated.Powerful quake shakes Indonesia

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 Southern Thailand, Southern Siam or Tambralinga is a southernmost cultural region of Thailand, separated from Central Thailand region by the Kra Isthmus. Geography Southern Thailand is on the Malay Peninsula, with an area of around , boun ...

. In

Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...

, which is about 670 km from the epicenter, the tremor was felt at around 11:10 UTC (19:10

). Most of the

Central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known a ...

and

Eastern Eastern may refer to: Transportation *China Eastern Airlines, a current Chinese airline based in Shanghai *Eastern Air, former name of Zambia Skyways *Eastern Air Lines, a defunct American airline that operated from 1926 to 1991 * Eastern Air L ...

part of

had felt the tremor. In

Peninsular Malaysia Peninsular Malaysia ( ms, Semenanjung Malaysia; Jawi: سمننجڠ مليسيا), or the States of Malaya ( ms, Negeri-negeri Tanah Melayu; Jawi: نڬري-نڬري تانه ملايو), also known as West Malaysia or the Malaysian Peninsula, ...

, tremors were reported after 19:15

, including

Kuala Lumpur , anthem = ''Maju dan Sejahtera'' , image_map = , map_caption = , pushpin_map = Malaysia#Southeast Asia#Asia , pushpin_map_caption = , coordinates = , sub ...

, Putrajaya, Johor Bahru,

Malacca Malacca ( ms, Melaka) is a state in Malaysia located in the southern region of the Malay Peninsula, next to the Strait of Malacca. Its capital is Malacca City, dubbed the Historic City, which has been listed as a UNESCO World Heritage Site s ...

and

Penang Penang ( ms, Pulau Pinang, is a Malaysian state located on the northwest coast of Peninsular Malaysia, by the Malacca Strait. It has two parts: Penang Island, where the capital city, George Town, is located, and Seberang Perai on the Ma ...

. 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

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

. 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 ) , anthem = "''Advance Australia Fair''" , song_type = , song = , image_map = Australia on the globe (Cocos (Keeling) Islands special) (Southeast Asia centered).svg , map_alt = Location of the Cocos (Keeling) Islands , map_caption = ...

. Sumatra was taken off tsunami alert after two hours. A weak tsunami caused some damage in Serangai, located north of

. 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: ; often abbreviated as GoI), known as the Union Government or Central Government but often simply as the Centre, is the national government of the Republic of India, a federal democracy located in South Asia, ...

asked the states of

Tamil Nadu Tamil Nadu (; , TN) is a state in southern India. It is the tenth largest Indian state by area and the sixth largest by population. Its capital and largest city is Chennai. Tamil Nadu is the home of the Tamil people, whose Tamil languag ...

Kerala Kerala ( ; ) is a 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 regions of Cochin, Malabar, South C ...

Andhra Pradesh Andhra Pradesh (, abbr. AP) is a state in the south-eastern coastal region of India. It is the seventh-largest state by area covering an area of and tenth-most populous state with 49,386,799 inhabitants. It is bordered by Telangana to t ...

and the union territories of

Andaman and Nicobar Islands The Andaman and Nicobar Islands is a union territory of India consisting of 572 islands, of which 37 are inhabited, at the junction of the Bay of Bengal and the Andaman Sea. The territory is about north of Aceh in Indonesia and separated ...

and Puducherry to be on high alert. By late 12 September, the tsunami warning was recalled. Similarly, a tsunami alert was issued in

at 20:50 (

) for the coastal areas of

Perlis Perlis, ( Northern Malay: ''Peghelih''), also known by its honorific title Perlis Indera Kayangan, is the smallest state in Malaysia by area and population. Located on the northwest coast of Peninsular Malaysia, it borders the Thai provinces ...

Kedah Kedah (), also known by its honorific Darul Aman and historically as Queda, is a state of Malaysia, located in the northwestern part of Peninsular Malaysia. The state covers a total area of over 9,000 km2, and it consists of the mainla ...

Perak Perak () is a 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, Kelantan and Pahang to the east, and Selangor to the south. Thailand's ...

and

; 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 United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, an ...

, the earthquake was caused by

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

ing on the boundary between the

Australian Plate The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke ...

and the

Sunda Plate The Sunda Plate is a minor tectonic plate straddling the Equator in the Eastern Hemisphere on which the majority of Southeast Asia is located. The Sunda Plate was formerly considered a part of the Eurasian Plate, but the GPS measurements have ...

. 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 the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

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 8.5 earthquake, at the northern end of the aftershock zone. The magnitude 8.5 earthquake was the most powerful earthquake of 2007 to date, more powerful than the two

March 2007 Sumatra earthquakes The March 2007 Sumatra earthquakes occurred near the northern end of Lake Singkarak in Sumatra, Indonesia, on March 6. The first shock in this earthquake doublet struck with a maximum Mercalli intensity of VIII (''Severe'') and the second sho ...

nearby and the

2007 Peru earthquake The 2007 Peru earthquake, which measured 8.0 on the moment magnitude scale, hit the central coast of Peru on August 15 at 23:40:57 UTC (18:40:57 local time) and lasted two minutes. The epicenter was located south-southeast of Lima at a depth ...

. It was the second most powerful earthquake since the magnitude 9.3

2004 Indian Ocean earthquake An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time ( UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Su ...

, exceeded only by the magnitude 8.6

2005 Nias–Simeulue earthquake The 2005 Nias–Simeulue earthquake occurred on 28 March off the west coast of northern Sumatra, Indonesia. At least 915 people were killed, mostly on the island of Nias. The event caused panic in the region, which had already been devastated b ...

. 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

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 ranging from about one meter to one millimeter corresponding to frequency, frequencies between 300 MHz and 300 GHz respectively. Different sources define different fre ...

sensor aboard the Daichi(ALOS)

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...

South Pagai South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz ...

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. Co ...

as well as enlarging existing islands.Southern Sumatra Earthquake in 2007, coastal change, GSI
/ref>

References

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 The Pacific Tsunami Warning Center (PTWC) is one of two tsunami warning centers that are operated by NOAA in the United States. Headquartered on Ford Island, HI, the PTWC is part of an international tsunami warning system (TWS) program and s ...

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...