The 1976 Longling earthquake in

Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, sli ...

, was a

doublet earthquake __NOTOC__ In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as sing ...

, with two main shocks striking just east of Longling at 12:23:20 and 14:00:22 UTC (20:23 and 22:00 local time). The magnitudes were estimated at 6.7 and 6.6, respectively, on the scale, and 6.9 and 7.0 on the scale; Chinese sources put these at 7.4 and 7.3 on the scale. The region is noted for the quantity and intensity of its earthquakes, and the complexity of its tectonics, which are closely related to the collision between the Indian and Eurasian tectonic plates. No one died in the Longling county town Loss in the 9 counties in Baoshan, Lincang and Dehong were 98 deaths, 451 severe injuries and 1991 light injuries. 420,000 buildings collapsed in an area of 1883 square kilometers.

Geology

Yunnan is a mountainous region lying east of

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, ...

, and north of the

Red River Fault The Red River Fault or Song Hong Fault ( vi, Đới Đứt Gãy Sông Hồng) is a major fault in Yunnan, China and Vietnam which accommodates continental China's ( Yangtze Plate) southward movement It is coupled with that of the Sagaing Fault ...

that strikes southeast along the Red River into

North Vietnam North Vietnam, officially the Democratic Republic of Vietnam (DRV; vi, Việt Nam Dân chủ Cộng hòa), was a socialist state supported by the Soviet Union (USSR) and the People's Republic of China (PRC) in Southeast Asia that existed f ...

and the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

. The Red River fault is deep – some believe it may reach the

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years ...

– and forms a major tectonic boundary that separates Indochina from the

South China block The Yangtze Plate, also called the South China Block or the South China Subplate, comprises the bulk of southern China. It is separated on the east from the Okinawa Plate by a rift that forms the Okinawa Trough which is a back-arc basin, on the ...

. The seismotectonics of Yunnan and the adjacent areas is driven by the collision of the

Indian Plate The Indian Plate (or India Plate) is a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian Plate broke away from the other fragments of Gondwana , began m ...

with the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

. This has uplifted the

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the T ...

(and the Himalaya Mountains) and forced it eastwards, pushing the

South China Block The Yangtze Plate, also called the South China Block or the South China Subplate, comprises the bulk of southern China. It is separated on the east from the Okinawa Plate by a rift that forms the Okinawa Trough which is a back-arc basin, on the ...

and Indochina towards the westward subducting

Philippine Sea Plate The Philippine Sea Plate or the Philippine Plate is a tectonic plate comprising oceanic lithosphere that lies beneath the Philippine Sea, to the east of the Philippines. Most segments of the Philippines, including northern Luzon, are part of ...

and creating various extensional structures. All of this has created a complicated geological structure with many faults, which in western Yunnan has allowed heat and fluids from the subducting Indian Plate to rise into the upper crust, creating the Tengchong volcanic field to the north of Longling and the Longling fault (location of the first event), and west of the

Nu River , ''Mae Nam Salawin'' ( , name_etymology = , image = Sweet_View_of_Salween_River_in_Tang_Yan_Township,_Shan_State,_Myanmar.jpg , image_size = , image_caption = Salween River in Shan State, Myanmar , map ...

and Nu River fault (location of the second event). It appears that igneous intrusions have weakened the bedrock in this area, which has led to uneven accumulations of stress, which caused the earthquake..

Notes

Sources

* * * * . * . * . * . * (in Chinese with English abstract). * . *

External links

* 1976 Longling 1976 in China 1976 earthquakes Geography of Baoshan, Yunnan Earthquakes in Myanmar 1976 disasters in China {{China-stub

Geology

See also

Notes

Sources

External links