The 1950 Assam–Tibet earthquake, also known as the Assam earthquake, occurred on 15 August and had a

moment magnitude 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 pape ...

of 8.6. The epicentre was located in the

Mishmi Hills The Mishmi Hills are located at the northeastern tip of India, in northeastern Arunachal Pradesh. On the Chinese side, they form the southern parts of Nyingchi Prefecture in the Tibet Autonomous Region. These hills occur at the junction of No ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, known in Chinese as the Qilinggong Mountains (), south of the

Kangri Karpo Kangri Karpo (), also spelt Gangri Garbo (), is a mountain range in eastern Tibet, located primarily in Nyingchi Prefecture as well as a portion of Qamdo Prefecture in the Tibet Autonomous Region, China. The mountain range lies to the east of the ...

and just east of the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...

in the

North-East Frontier Agency The North-East Frontier Agency (NEFA), originally known as the North-East Frontier Tracts (NEFT), was one of the political divisions in British India, and later the Republic of India until 20 January 1972, when it became the Union Territory of ...

part of

Assam Assam (; ) is a state in northeastern India, south of the eastern Himalayas along the Brahmaputra and Barak River valleys. Assam covers an area of . The state is bordered by Bhutan and Arunachal Pradesh to the north; Nagaland and Manipur ...

. This area, south of the

McMahon Line The McMahon Line is the boundary between Tibet and British India as agreed in the maps and notes exchanged by the respective plenipotentiaries on 24–25 March 1914 at Delhi, as part of the 1914 Simla Convention. The line delimited the res ...

and now known as

Arunachal Pradesh Arunachal Pradesh (, ) is a state in Northeastern India. It was formed from the erstwhile North-East Frontier Agency (NEFA) region, and became a state on 20 February 1987. It borders the states of Assam and Nagaland to the south. It shares int ...

, is today disputed between

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

and India. It is the strongest earthquake ever recorded on land. Occurring on a Tuesday evening at 7:39 pm

Indian Standard Time Indian Standard Time (IST), sometimes also called India Standard Time, is the time zone observed throughout India, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments. In military and avia ...

, the

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 ...

was destructive in both

(India) and

Tibet Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa people, ...

(China), and approximately 4,800 people were killed. The earthquake is notable as being the largest recorded quake caused by

continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains prod ...

rather than

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

, and is also notable for the loud noises produced by the quake and reported throughout the region.

Geology

In an attempt to further uncover the seismic history of

Northeast India , native_name_lang = mni , settlement_type = , image_skyline = , image_alt = , image_caption = , motto = , image_map = Northeast india.png , ...

, field studies were conducted by scientists with the

National Geophysical Research Institute The National Geophysical Research Institute (NGRI) is a geoscientific research organization established in 1961 under the Council of Scientific and Industrial Research (CSIR), India's largest Research and Development organization. It is suppo ...

and

Institute of Physics, Bhubaneswar Institute of Physics, Bhubaneswar ( or, ପଦାର୍ଥ ବିଜ୍ଞାନ ଅନୁଷ୍ଠାନ) is an autonomous research institution of the Department of Atomic Energy (DAE), Government of India. The institute was founded by Profes ...

. The study discovered signs of soil liquefaction including sills and

sand volcano Sand boils or sand volcanoes occur when water under pressure wells up through a bed of sand. The water looks like it is boiling up from the bed of sand, hence the name. Sand volcano A sand volcano or sand blow is a cone of sand formed by the ...

es inside of at least twelve

trench A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches result from ero ...

es in

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

s and on the Burhi Dihing River Valley that were formed by past

seismic activity 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, fr ...

Radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was dev ...

identified the deposits at roughly 500 years old, which would correspond with a recorded earthquake in 1548.

Earthquake

The earthquake occurred in the rugged mountainous areas between the

and the Hengduan Mountains. The earthquake was located just south of the

between India and Tibet, and had devastating effects in both regions. Today this area is claimed as part of

Zayü Zayul County ()
KNAB, retrieved 5 July 2021. Mêdog Counties in the

Tibet Autonomous Region The Tibet Autonomous Region or Xizang Autonomous Region, often shortened to Tibet or Xizang, is a Provinces of China, province-level Autonomous regions of China, autonomous region of the China, People's Republic of China in Southwest China. I ...

by China, and as part of

Lohit District Lohit () is an administrative district in the state of Arunachal Pradesh in India. The district headquarters is located at Tezu. As of 2011 it is the third most populous district of Arunachal Pradesh, after Papum Pare and Changlang. Etymology ...

by India. This great earthquake has a calculated magnitude of 8.6 and is regarded as one of the most important since the introduction of seismological observing stations. It was the sixth largest earthquake of the 20th century. It is also the largest known earthquake to have not been caused by an oceanic

. Instead, this quake was caused by two continental plates colliding.

Aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

s were numerous; many of them were of magnitude 6 and over and well enough recorded at distant stations for reasonably good

epicentre 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 ...

location. From such data the Indian Seismological Service established an enormous geographical spread of this activity, from about 90 deg to 97 deg east longitude, with the epicentre of the great earthquake near the eastern margin.

Impact

The 1950 Assam–Tibet earthquake had devastating effects on both Assam and Tibet. In Assam, 1,526 fatalities were recorded and another 3,300 were reported in Tibet for a total of approximately 4,800 deaths. Alterations of relief were brought about by many rock falls in the Mishmi Hills and surrounding forested regions. In the Abor Hills, 70 villages were destroyed with 156 casualties due to landslides. Landslides blocked the tributaries of the

Brahmaputra The Brahmaputra is a trans-boundary river which flows through Tibet, northeast India, and Bangladesh. It is also known as the Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, Luit in Assamese, and Jamuna River in Bangla. It ...

. In the

Dibang Valley Dibang Valley (Pron:/dɪˈbæŋ/) is a district of Arunachal Pradesh named after the Dibang River or the Talon as the Mishmis call it. It is the least populated district in India and has an area of . History In June 1980, Dibang Valley distri ...

, a landslide lake burst without causing damage, but another at Subansiri River opened after an interval of 8 days and the wave, high, submerged several villages and killed 532 people. The shock was more damaging in Assam, in terms of property loss, than the earthquake of 1897. In addition to the extreme shaking, there were floods when the rivers rose high after the earthquake bringing down sand, mud, trees, and all kinds of debris. Pilots flying over the meizoseismal area reported great changes in topography. This was largely due to enormous

landslides Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, ...

, some of which were photographed. In Tibet,

Heinrich Harrer Heinrich Harrer (; 6 July 1912 – 7 January 2006) was an Austrian mountaineer, sportsman, geographer, ''Oberscharführer'' in the ''Schutzstaffel'' (SS), and author. He was a member of the four-man climbing team that made the first ascent of th ...

reported strong shaking in

Lhasa Lhasa (; Lhasa dialect: ; bo, text=ལྷ་ས, translation=Place of Gods) is the urban center of the prefecture-level city, prefecture-level Lhasa (prefecture-level city), Lhasa City and the administrative capital of Tibet Autonomous Regio ...

and loud cracking noises from the earth. Aftershocks were felt in Lhasa for days. In Rima, Tibet (modern-day

Zayü Zayul County ()
KNAB, retrieved 5 July 2021. Frank Kingdon-Ward Francis Kingdon-Ward, born Francis Kingdon Ward OBE, (6 November 1885 in Manchester – 8 April 1958) was an English botanist, explorer, plant collector and author. He published most of his books as Frank Kingdon-Ward and this hyphenated for ...

, noted violent shaking, extensive slides, and the rise of the streams. Helen Myers Morse, an American missionary living in Putao, northern

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

at the time, wrote letters home describing the main shake, the numerous aftershocks, and of the noise coming out of the earth. One of the more westerly aftershocks, a few days later, was felt more extensively in Assam than the main shock. This led certain journalists to the belief that the later shock was 'bigger' and must be the greatest earthquake of all time. This is a typical example of the confusion between the essential concepts of magnitude and intensity. The extraordinary sounds heard by Kingdon-Ward and many others at the times of the main earthquake have been specially investigated.

Seiche A seiche ( ) is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors, caves and seas. The key requirement for formation of ...

s were observed as far away as Norway and England. (p. 63–64.)

Future threat

An article in ''

Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

'', published in response to the

2001 Bhuj earthquake The 2001 Gujarat earthquake, also known as the Bhuj earthquake, occurred on 26 January, India's 52nd Republic Day, at . The epicentre was about 9 km south-southwest of the village of Chobari in Bhachau Taluka of Kutch District of Gujara ...

, calculated that 70 percent of the

could experience an extremely powerful earthquake. The prediction came from research of the historical records from the area as well as the presumption that since the 1950 Medog earthquake enough slippage has taken place for a large earthquake to occur. In 2015, the Himalayas were hit by a 7.8-magnitude earthquake with an epicenter further west in Nepal.

References

External links