1881 Nicobar Islands earthquake
Encyclopedia
The 1881 Nicobar Islands earthquake occurred at about 07:49 local time (01:49 UTC
) on 31 December, with an epicentre
beneath Car Nicobar
. It occurred as two separate ruptures, the largest of which had an estimated magnitude of 7.9 on the moment magnitude scale
and triggered a tsunami
that was observed around the Bay of Bengal
. It is probably the earliest earthquake
for which rupture parameters have been estimated instrumentally.
are a series of volcanic islands that are part of an active volcanic arc
, formed above the subduction zone
where the Indo-Australian Plate
passes beneath the Burma Plate
. The convergence along this plate boundary is highly oblique, with the plate vector running at a low angle to the boundary. Most of the strike-slip component of the convergence is accommodated by the Great Sumatran fault
, which passes northwards into the Andaman Sea
spreading centre. This plate boundary has been the location of many historical megathrust earthquake
s. The 1881 rupture area lies almost entirely within that for the Mw
= 9.2 2004 Indian Ocean earthquake
, while rupturing less than a third of its down-dip width.
, including an infantry barrack and a chimney, both of which suffered severe cracking. On Car Nicobar the coconut plantations and native huts were extensively damaged and sand volcano
es were observed. There were no reported casualties associated with either the earthquake or the subsequent tsunami.
, Burma and Sumatra
, a total area of 2000000 square miles (5,179,976.2 km²). The rupture area, and therefore the magnitude, has been calculated by modelling the observed tsunami arrival times and heights. Two rupture areas have been identified. The larger, and more southerly, measured 150 km x 60 km dipping about 20° to the east with a displacement of 2.7 metres (8.9 ft) and a smaller area to the north dipping 15° to the east with a displacement of 0.9 m (3 ft). The larger gives an estimated Mw = 7.9 event and the smaller a Mw = 7.0 event.
s around the Bay of Bengal that had recently been deployed by the Great Trigonometric Survey
of India. The ten gauges on the Indian mainland were synchronised using a telegraph to Madras (Chennai
) time, while that at Port Blair was set by a chronometer
linked to local time. The maximum recorded wave height was 1.22 m (4 ft) at Nagapattinam
.
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) on 31 December, with an epicentre
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
beneath Car Nicobar
Car Nicobar
Car Nicobar is the northernmost of the Nicobar Islands. It is also one of two local administrative divisions of the Indian district of Nicobar, part of the Indian union territory of Andaman and Nicobar Islands....
. It occurred as two separate ruptures, the largest of which had an estimated magnitude of 7.9 on the moment magnitude scale
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...
and triggered 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...
that was observed around the Bay of Bengal
Bay of Bengal
The Bay of Bengal , the largest bay in the world, forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered mostly by the Eastern Coast of India, southern coast of Bangladesh and Sri Lanka to the west and Burma and the Andaman and Nicobar Islands to the...
. It is probably the earliest 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...
for which rupture parameters have been estimated instrumentally.
Tectonic setting
The Nicobar IslandsNicobar Islands
The Nicobar Islands are an archipelagic island chain in the eastern Indian Ocean...
are a series of volcanic islands that are part of an active volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
, formed above the subduction zone
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"...
where the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
passes beneath the Burma Plate
Burma Plate
The Burma Plate is a small tectonic plate or microplate located in Southeast Asia, often considered a part of the larger Eurasian Plate. The Andaman Islands, Nicobar Islands, and northwestern Sumatra are located on the plate...
. The convergence along this plate boundary is highly oblique, with the plate vector running at a low angle to the boundary. Most of the strike-slip component of the convergence is accommodated by the Great Sumatran fault
Great Sumatran fault
The Indonesian island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone and the associated Sunda Arc off the west coast of the island, Sumatra also has a large strike-slip fault, the so-called Great Sumatran Fault, running the entire length of the island...
, which passes northwards into the Andaman Sea
Andaman Sea
The Andaman Sea or Burma Sea is a body of water to the southeast of the Bay of Bengal, south of Burma, west of Thailand and east of the Andaman Islands, India; it is part of the Indian Ocean....
spreading centre. This plate boundary has been the location of many 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 1881 rupture area lies almost entirely within that for the 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...
= 9.2 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...
, while rupturing less than a third of its down-dip width.
Damage
The Andaman and Nicobar Islands suffered some damage, although the only masonry buildings affected were in Port BlairPort Blair
Port Blair is the largest town and a municipal council in Andaman district in the Andaman Islands and the capital of the Andaman and Nicobar Islands, a union territory of India...
, including an infantry barrack and a chimney, both of which suffered severe cracking. On Car Nicobar the coconut plantations and native huts were extensively damaged and sand volcano
Sand volcano
A sand volcano or sand blow is a cone of sand formed by the ejection of sand onto a surface from a central point. The sand builds up as a cone with slopes at the sand's angle of repose. A crater is commonly seen at the summit...
es were observed. There were no reported casualties associated with either the earthquake or the subsequent tsunami.
Earthquake
The earthquake was very widely felt with reports from many parts of mainland IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Burma and 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...
, a total area of 2000000 square miles (5,179,976.2 km²). The rupture area, and therefore the magnitude, has been calculated by modelling the observed tsunami arrival times and heights. Two rupture areas have been identified. The larger, and more southerly, measured 150 km x 60 km dipping about 20° to the east with a displacement of 2.7 metres (8.9 ft) and a smaller area to the north dipping 15° to the east with a displacement of 0.9 m (3 ft). The larger gives an estimated Mw = 7.9 event and the smaller a Mw = 7.0 event.
Tsunami
The tsunami was recorded by eleven of a series of continuous tide gaugeTide gauge
A tide gauge is a device for measuring sea level and detecting tsunamis.Sensors continuously record the height of the water level with respect to a height reference surface close to the geoid...
s around the Bay of Bengal that had recently been deployed by the Great Trigonometric Survey
Great Trigonometric Survey
The Great Trigonometric Survey was a project of the Survey of India throughout most of the 19th century. It was piloted in its initial stages by William Lambton, and later by George Everest. Among the many accomplishments of the Survey were the demarcation of the British territories in India and...
of India. The ten gauges on the Indian mainland were synchronised using a telegraph to Madras (Chennai
Chennai
Chennai , formerly known as Madras or Madarasapatinam , is the capital city of the Indian state of Tamil Nadu, located on the Coromandel Coast off the Bay of Bengal. Chennai is the fourth most populous metropolitan area and the sixth most populous city in India...
) time, while that at Port Blair was set by a chronometer
Chronometer
Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...
linked to local time. The maximum recorded wave height was 1.22 m (4 ft) at Nagapattinam
Nagapattinam
Nagapattinam is a town in the Indian state of Tamil Nadu and the administrative headquarters of Nagapattinam District. It is a prominent seaport on the east coast of India and an important centre of trade and commerce.The town of Nagapattinam dates back to the Sangam period...
.