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==Comparison==
==Comparison==
Within China's geography, the deadliest known earthquake in [[history]] occurred in 1556 in [[Shaanxi]]. The [[1556 Shaanxi earthquake]] is estimated to have killed 830,000 people, although figures from this period are hard to verify.<ref>[http://neic.usgs.gov/neis/eqlists/eqsmosde.html]{{dead|date=July 2018}}</ref> The [[1920 Haiyuan earthquake]] in [[Gansu Province]] killed an estimated 235,000. In 1927 another earthquake struck in the same area, this time at [[Xining]]; measuring 8.6 on the Richter scale, it resulted in 200,000 deaths. Among the earthquakes that caused an extreme loss of life in the same decade is the [[1923 Great Kantō earthquake]], which killed 143,000 in [[Tokyo]] in 1923.{{cn|date=July 2018}}
Within China's geography, the deadliest known earthquake in [[history]] occurred in 1556 in [[Shaanxi]]. The [[1556 Shaanxi earthquake]] is estimated to have killed 830,000 people, although figures from this period are hard to verify.<ref name="Int">International Association of Engineering Geology International Congress. Proceedings. [1990] (1990). {{ISBN|90-6191-664-X}}.</ref> The [[1920 Haiyuan earthquake]] in [[Gansu Province]] killed an estimated 235,000. In 1927 another earthquake struck in the same area, this time at [[Xining]]; measuring 8.6 on the Richter scale, it resulted in 200,000 deaths. Among the earthquakes that caused an extreme loss of life in the same decade is the [[1923 Great Kantō earthquake]], which killed 143,000 in [[Tokyo]] in 1923.{{cn|date=July 2018}}


The [[2008 Sichuan earthquake]] was equally powerful at 8.0 on the Richter scale. However, it occurred in a mountainous region where relief efforts were noticeably hampered by the geographical make-up of the land nearby. Nevertheless, the Sichuan earthquake had a much quicker and more organized response system than Tangshan, as the political, social and technological environment was different. The Chinese government allowed international aid and open media access to the disaster area.{{Citation needed|date=December 2014}}
The [[2008 Sichuan earthquake]] was equally powerful at 8.0 on the Richter scale. However, it occurred in a mountainous region where relief efforts were noticeably hampered by the geographical make-up of the land nearby. Nevertheless, the Sichuan earthquake had a much quicker and more organized response system than Tangshan, as the political, social and technological environment was different. The Chinese government allowed international aid and open media access to the disaster area.{{Citation needed|date=December 2014}}

Revision as of 20:40, 28 July 2018

Tangshan earthquake
UTC timeDoublet earthquake:    
 A: 1976-07-27 19:42:55
 B: 1976-07-28 10:45:36
ISC event 
 A: 711732
 B: 711773
USGS-ANSS 
 A: ComCat
 B: ComCat
Local date28 July 1976
Local timePeking time:
 A: 03:43
 B: 18:45
Magnitude 
 A: 7.6 Mw; 7.6 Ms [1]
 B: 7.0 Mw; 7.4 Ms [2]
DepthA: 12.2 km[3]
B: 16.7 km[4]
Epicenter39°38′N 118°06′E / 39.63°N 118.10°E / 39.63; 118.10 39°43′N 118°26′E / 39.72°N 118.44°E / 39.72; 118.44
Areas affectedPeople's Republic of China
Casualties242,769–700,000 dead (3rd deadliest earthquake of modern history)

The 1976 Tangshan earthquake, also known as the Great Tangshan earthquake,[5] was a natural disaster resulting from a magnitude 7.6 earthquake that hit the region around Tangshan (in Hebei, People's Republic of China) on July 28, 1976, at 3:42 in the morning. In minutes the city of Tangshan, an industrial city with approximately one million inhabitants, ceased to exist. Eight-five percent of the buildings in the city collapsed or were unusable, all services failed, and most of the highway and railway bridges collapsed or were seriously damaged.[6] At least 242,000 people died (some say three times that), making this the third (or possibly second) deadliest earthquake in recorded history.[7]

The earthquake occurred at a turbulent time in Chinese recent history, during a series of political events involving the Communist Party of China including the expulsion of the ruling Gang of Four by Mao Zedong's chosen successor, Hua Guofeng. In traditional Chinese thought, natural disasters are sometimes seen as precursors of dynastic change.[8]

Tangshan earthquake
Map
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Maps: terms of use
75km
50miles
none
Sea of Bohai
Changli
Ninghe
Qinglong
Qinhuangdao
Zunhua
Tianjin
Beijing
A
B
Tangshan
Diamonds mark the epicenters of the main (A) and secondary (B) shocks.

The earthquakes

The quake struck at 3:42:56 in the morning (local time), approximately 12 km under the southern part of Tangshan.[9] The magnitude was initially estimated at around 8.1, subsequently recalculated to be 7.6 on the standard Mw scale.[10] However, that scale measures only the total energy released by an earthquake, and earthquakes vary in how much of that energy is converted to seismic shaking. The Tangshan quake, being relatively shallow, converted much of its energy to surface shaking, and on the Ms (surface magnitude) scale it also measured 7.6. (7.8 on the Chinese surface magnitude scale.[11])

The earthquake was complex, with multiple events. The main shock "occurred on a near vertical right-lateral strike-slip fault, striking N40°E",[12] the block on the southeast side sliding about three meters to the southwest.[13] This resulted from tectonic compression on a nearly west-east axis.[14] Surface rupturing occurred in five en echelon segments extending eight kilometers through the center of Tangshan.[15]

A long sequence of aftershocks followed, with twelve of magnitude 6 or greater.[16] The largest of these, with a magnitude 7.0 Mw , or 7.4 Ms , struck at 18:45 near Luanhsien (Luanxian), about 70 km to the east-northeast, just south of the northeastern end of the Tangshan fault (near the "B" on the map).[17] This occurred in a zone of north-northwest striking conjugate faults that cut across the north end of the Tangshan fault. The left-lateral motion here, along with the right-lateral motion on the Tangshan fault, suggests that as the crustal blocks to the west and east are compressed together the block between these two earthquakes is being squeezed out to the south. The southern end of the fault, near Ninghe, was struck at 7:17 by an M 6.2 aftershock.[18] Most aftershocks occurred between these end points, in a zone 140 km long and about 50 km wide.[19] Many buildings were further damaged by the aftershocks.[20]

Damage

The damage done by an earthquake depends primarily on two factors. First, the intensity of shaking, which depends mainly on the magnitude of the earthquake rupture, the distance from the epicenter, and the nature of the local soil and topography, with soft soils (e.g., sediments and fill) more likely to amplify the intensity and duration of the shaking.[21] Second, the design and construction of the structures being shaken, with houses built of adobe or stone, wooden houses without a well-built frame, and unreinforced masonry construction being especially vulnerable.[22] In this respect Tangshan was very unfortunate, in that the seismic risk had been greatly underestimated, and almost all buildings and structures were designed and built without seismic considerations.[23] As a result, Tangshan was "mainly a city of unreinforced brick buildings",[24] sitting right on top of a major earthquake.

The power (magnitude) of the Tangshan earthquake is indicated by the extent of where it was felt: up to 1,100 km (680 mi) away, across most of northeastern China, and even in Mongolia and Korea.[25] In and around Beijing, 140 km (87 mi) from the epicenter, the shaking reached an intensity of VI on the Chinese intensity scale (similar to the Modified Mercalli Intensity Scale), with nearly 10% of all buildings damaged,[26] and at least 50 people died.

Intensity XI and X zone

Tangshan was not so fortunate. The rupture occurred under the southern part of the city, and propagated northeastward on a fault that runs through the middle of the city. The maximum intensity was "XI" (eleven) on the 12-degree Chinese scale. Nearly every building and structure in the city collapsed, wholly or partially, infrastructure was severely damaged, and essential services such as electric power, water supply, and communications were entirely knocked out. This area of maximum damage – the meizoseismal area – was approximately 10.5 kilometres (6.5 mi) long and from 3.5 to 5.5 km wide, centered roughly along the railway.[27]

The area of intensity X shaking – where only new, one-story brick buildings were merely "damaged or slightly damaged", the rest being severely damaged or worse – was 36 km long and 15 km across.[28] In this "high intensity" zone (intensity X and XI) 20 highway bridges and five railway bridges cross the Douhe River in Tangshan; only six survived with only minor damage.[29]

Intensity IX and VIII zone

Shaking of intensity IX (or greater) occurred in a zone roughly 78 km (48 mi) long and 42 km (26 mi) (about 1800 km2, and also around the aftershocks at Luanxian and Ninghe. In this zone most buildings classified as Class III (well-built buildings of wood, masonry, or reinforced concrete[30]) survived,[31] but many Class II buildings (typically old wood-frame buildings lacking a well-built frame, and quite common outside of the cities) were destroyed, while a majority of Class I buildings (built of adobe or stone) were destroyed.

Further out, and around the city of Tianjin and a few isolated patches, intensity VIII shaking mostly affected Class I buildings (more than half destroyed), bridges, and tall brick chimneys. Railway track was also subject to bending or displacement, depending on soil conditions.[32]

Intensity VII zone

The zone of intensity VII shaking marks the extent of serious damage, where many Class I structure were damaged but only "few" — between 10% and 30% — were destroyed, and only a "few" Class two buildings damaged. This ellipsoid zone extended about 75 km north and south of Tangsan and 120 km east and west, from about 25 km short of Beijing to Qinhuangdao City, and from the Sea of Bohai in the south and southwest to just north of Zunhua. The north-south shortening of this zone is attributed to outcropping of bedrock of the Yanshin mountains.

Significant damage occurred beyond this in the VI zone, but (like in Beijing) affected less than 10% of the buildings, or occurred in small localized areas.[33]

The economic loss totaled to 10 billion yuan.[34]

Death toll

Estimates of the number of deaths due to the Tangshan earthquake have varied widely, and generally lack a clear (let alone authoritative) basis. One of the earliest reports outside of China came on the 28th[35] from the International Tsunami Information Center, reporting that a "violent" earthquake, initially estimated at about magnitude 8.1, had struck "in the vicinity of Peking" (the older name for Beijing). Center Director Dr. George Pararas-Carayannis was reported as saying that "if the quake hit in a populated area reports of considerable damage could be expected."[36]

News reports the next day located the quake "about 100 miles southeast of Peking and 63 miles northeast of Tientsen" (Tianjin); i.e., "almost precisely in Tangshan".[37] The Chinese Communist party's Central Committee also broadcast a statement that the quake "caused great losses to people's life and property". One of the first reports from Tangshan said "nearly every building in the city ... was flattened."[38] There were several reports of 50 people killed in Beijing, a hundred miles from the epicenter.

According to author Stephen Spignese, a "couple of days" after the quake Dr. Pararas-Carayannis gave United Press International (UPI) an estimate of 700,000 to 750,000 deaths, based on a similar sized earthquake in Shensi province in 1556 that caused 830,000 deaths.[39] Pararas-Carayannis' current web page[40] says only that "it was fairly accurately estimated that there were at least 655,000 people dead," without mentioning by whom or on what basis this estimate was made.

In August the Nationalist Chinese government in Taiwan announced that, according to their agents in China, the death toll was over 100,000, with about 900,000 injured. They also reported that "almost all buildings in Tangshan were levelled", and 80 percent of homes and buildings in Tientsin "suffered damage to some extent".[41]

The following January (1977) the Nationalists released a document they said had been presented at an emergency conference on relief work the previous August by the Hopeh Provincial Committee of the party and the Hopeh Revolutionary Committee.[42] According to this document: "in such seriously stricken areas as Tangshan municipality, and Fengnan and Feng-yun, there were 655,237 persons dead. Some 79,000 persons were seriously injured, and some 700,000 persons suffered various degrees of injuries." Though these figures have been widely cited, it does not appear there has ever been inquiry into how they were derived, of whether they were an initial estimate (made in the first few days following the quake), or had a more solid basis.

In following June it was reported[43] that the Chinese authorities had briefed Cinna Lomnitz (a noted Chilean/Mexican seismologist) about Tangshan. It was noted that though no figures were provided, they did not deny any published estimates.

A 1988 book by several members of the Chinese State Seismological Bureau states that no more than 242,419 people died in the quake.[44] It is unclear whether this number is merely the personal view of the authors, or an official view of the government. A webpage of the Chinese Earthquake Administration dated 2009 also attributes "242,769 deaths and 164,851 serious injuries" to the Tangshan quake.[45]

There are various reports that the "official death toll was later given by the Chinese government as 275,000",[46] but without specifying a source, and a thorough search has failed to locate any such official source in English. Chinese websites generally report only a lower bound: "more than 240,000".

Political aftermath

The earthquake came in one of the most dramatic years in the history of the People's Republic. The earthquake was preceded by the death of Zhou Enlai in earlier months and followed by the death of Mao Zedong in September. The political repercussions of the disaster and its aftermath contributed to the end of the Cultural Revolution. Mao's chosen successor Hua Guofeng showed concern, thereby solidifying his status as China's leader. He, along with Vice-Premier Chen Yonggui, made a personal visit to Tangshan on August 4 to survey the damage and was photographed in the tasks of cleaning up and comforting the survivors.[47]

Leaders who opposed the return of Deng Xiaoping, especially the group which became known as Gang of Four, filled the press with concern for the victims, but explicitly said that the nation should not be diverted by the earthquake, and that the priority was to denounce Deng instead. Jiang Qing was widely quoted as saying "There were merely several hundred thousand deaths. So what? Denouncing Deng Xiaoping concerns 800 million people."[48] Other Gang of Four slogans said: "Be alert to Deng Xiaoping's criminal attempt to exploit earthquake phobia to suppress revolution!"[49]

Geology

Tangshan lies at the northern edge of the Beijing-Tianjin-Tangshan Plain, an alluvial plain that stretches from Beijing to the Sea of Bohai.[50] This plain – the northeastern corner of the great North China Plain – is where sediments eroded from the Yanshan mountains to the north have filled in the ancient Sea of Bohai, with Tangshan near where the shore was about 4,000 years ago.[51] To the south these sediments have formed a layer of weak soils as much as three kilometers thick. At Tangshan and northward these sediments are thinner where the underlying strata crops out to form isolated hills.[52] This underlying strata is a thick (typically 10 km) layer of mainly sedimentary strata such as limestone and sandstone, with large deposits of coal.[53] Tangshan is located particularly over a northeast oriented syncline, a fold in the sedimentary strata that has brought massive deposits of coal close enough to the surface to be mined. In this area the overlying alluvium varies in thickness from several meters to around 600 m (2,000 ft).[54]

Underlying all this is the ancient bedrock of different kinds of metamorphic rock (such as schist, gneiss, quartz, granulite, etc.) that form the Eastern Block of the North China Craton.[55] This craton was formed approximately two billion years ago[56] by the collision of two major crustal blocks that left a belt of uplifted mountains – the Central Orogenic Belt (COB) – that crosses China approximately southwest to northeast, passing just west and north of Beijing.[57] Just north of Zunhua another orogenic belt, the east-west trending Yanshan mountain fault-fold belt (also known as the Yanshan seismic belt) marks the northern edge of the North China Craton (and of the alluvial plain). It is also the location of over half of the destructive earthquakes in Hebi province,[58] as under the plain several fault zones (oriented parallel to the Central Orogenic Belt) terminate against the Yanshan mountains.

Many of these faults are ancient, but have been reactivated by the force transmitted from the collision of the Indian_Plate#Plate_movements against the Eurasian Plate[59], making the Eastern Block unusually active seismically, accounting for six of the ten deadliest earthquakes in recorded history.[60]

The Tangshan fault that ruptured 28 July runs right under the center of Tangshan City.[61] One of three faults in the Changdong fault zone, it runs approximately east-northeast (ENE) about 36 km to where it terminates (near the "B" on the map) against the fault where the secondary M 7.1 quake occurred. [62] The southern end of the Tangshan fault (it bends slightly at Tangshan) is near Ninghe, which was also the site of a M 6.2 earthquake several hours after the main shock. The Tangshan fault is considered shallow, but corresponds with a deeper and younger fault with somewhat differing characteristics.[63]

Comparison

Within China's geography, the deadliest known earthquake in history occurred in 1556 in Shaanxi. The 1556 Shaanxi earthquake is estimated to have killed 830,000 people, although figures from this period are hard to verify.[64] The 1920 Haiyuan earthquake in Gansu Province killed an estimated 235,000. In 1927 another earthquake struck in the same area, this time at Xining; measuring 8.6 on the Richter scale, it resulted in 200,000 deaths. Among the earthquakes that caused an extreme loss of life in the same decade is the 1923 Great Kantō earthquake, which killed 143,000 in Tokyo in 1923.[citation needed]

The 2008 Sichuan earthquake was equally powerful at 8.0 on the Richter scale. However, it occurred in a mountainous region where relief efforts were noticeably hampered by the geographical make-up of the land nearby. Nevertheless, the Sichuan earthquake had a much quicker and more organized response system than Tangshan, as the political, social and technological environment was different. The Chinese government allowed international aid and open media access to the disaster area.[citation needed]

See also

Notes

  1. ^ ISC-EHB Event 711732 [IRIS]..
  2. ^ ISC-EHB Event 711773 [IRIS]..
  3. ^ ISC-EHB Event 711732 [IRIS]..
  4. ^ ISC-EHB Event 711773 [IRIS]..
  5. ^ So-called by numerous sources, of which the voluminous work edited by Housner & He (2002) is the most notable.
  6. ^ Housner & He 2002, Prologue.
  7. ^ See the #Death toll section for the various fatality figures.
  8. ^ Pelling & Dill 2006.
  9. ^ Jennings 1980, p. 69.
  10. ^ ISC-EHB Event 711732 [IRIS]..
  11. ^ Zhu 2002, p. 6.
  12. ^ Butler, Stewart & Kanamori 1979, p. 207. See figure 12 (p. 218) for an illustration. See also Zhu 2002, p. 8, Guo 2002, pp. 33–34.
  13. ^ Jennings 1980, p. 89.
  14. ^ Lomnitz & Lomnitz 1978, p. 109; Jennings 1980, p. 88.
  15. ^ Jennings 1980, p. 89, and see figure 4.17.
  16. ^ Lomnitz & Lomnitz 1978, p. 109.
  17. ^ Jennings 1980, pp. 88, 92.
  18. ^ Zhu 2002, Table 4.
  19. ^ Jennings 1980, p. 88, and see figure 15 in Guo 2002, p. 45.
  20. ^ Jennings 1980, p. 75.
  21. ^ Butler, Stewart & Kanamori 1979, pp. 217–218. See also Jennings 1980, figure 4.23, which plots damage as a function of epicentral distance and a measure of building strength.
  22. ^ Jennings 1980, p. 19.
  23. ^ Jennings 1980, p. 75.
  24. ^ Jennings 1980, p. 69.
  25. ^ Jennings 1980, p. 69; Yang 2002b, p. 176 [6].
  26. ^ Yao 2002, p. 244 [74].
  27. ^ Yang 2002b, p. 172, and see figure 2, p. 182. An isoseismal map can be found in the front matter of Volume 4.
  28. ^ Yang 2002b, p. 172.
  29. ^ Mao, Liang & Cui 2002, p. 231
  30. ^ Jennings 1980, p. 10.
  31. ^ Yang 2002b, p. 180, Table 1.
  32. ^ Yang 2002b, p. 172.
  33. ^ Xu 2002, p. 242.
  34. ^ Stoltman, Lidstone & Dechano 2004.
  35. ^ From United Press International (UPI), and carried by many newspapers.
  36. ^ UPI, as seen in The Daily Texan, 28 July 1976, page 3.
  37. ^ UPI: as seen in The Daily Freeman (Kingston), 29 July, 1976, p. 32.
  38. ^ UPI: The Berkshire Eagle, 30 July 1976, p. 1.
  39. ^ Spignese (2005, pp. 47–48) quotes from a geocities.com webpage of "Dr. George" that is no longer available.
  40. ^ "The China Earthquake of 1976", retrieved 18 July 2018.
  41. ^ UPI: Pacific Stars and Stripes, 7 August, 1976, p. 11.
  42. ^ UPI: reported in The Redlands (California) Daily Facts, 5 January, 1977, p. 5.
  43. ^ Malcolm 1977, p. 1.
  44. ^ Chen et al. 1988.
  45. ^ "二十世纪以来死亡人数最多的地震", Chinese Earthquake Administration ["The most deadly earthquake since the twentieth century"].
  46. ^ E.g.: Housner & He 2002, p. 17, footnote.
  47. ^ Described in Palmer 2012, Ch.6, "I Live, You Die,".
  48. ^ Palmer (2012, p. 189) quoting from Jiaqi Yan,Gao Gao translated and edited by D.W.Y. Kwok., Turbulent Decade a History of the Cultural Revolution (Honolulu: University of Hawai'i Press, 1996), p. 514.
  49. ^ Palmer 2012, p. 191.
  50. ^ Jennings 1980, p. 77.
  51. ^ Jennings 1980, p. 84–85, and see figure 4.14.
  52. ^ Jennings 1980, p. 84; Xing & Zou 2002, p. 88.
  53. ^ Guo 2002, p. 27.
  54. ^ Zhao 2002, p. 626.
  55. ^ Guo 2002, p. 27.
  56. ^ Some say 1.8 Ga, others 2.5. See Kusky & Li 2003 and Kusky, Windley & Zhai 2007, p. 20 for details.
  57. ^ Kusky, Windley & Zhai 2007, p. 3.
  58. ^ Yang 2002a, p. 50.
  59. ^ Yang 2002a, p. 50.
  60. ^ Kusky, Windley & Zhai 2007, p. 20.
  61. ^ Jennings 1980, p. 89.
  62. ^ See figure 16 in Zhu 2002, p. 23, and figure 13 in Guo 2002, p. 43. The secondary quake occurred on a north oriented section of a fault in a zone that, coming from the southeast, turns north, and then gets complicated.
  63. ^ Guo 2002, pp. 30–31.
  64. ^ International Association of Engineering Geology International Congress. Proceedings. [1990] (1990). ISBN 90-6191-664-X.

Sources

  • Chen, Yong; Tsoi, Kam-Ling; Chen, Feibi; Gao, Zhenhuan; Zou, Qijia; Chen, Zhangli, eds. (1988), The Great Tangshan Earthquake of 1976: An Anatomy of Disaster, Oxford: Pergamon Press, p. 153, ISBN 0080348750, LCCN 88005916
  • Guo, Shunmin (2002), "Occurrence of the Tangshan Earthquake from the View of Fault Block Movement", in Housner, George W.; He, Duxin (eds.), Report On The Great Tangshan Earthquake of 1976, vol. Volume 1, Pasadena, California: Earthquake Engineering Research Laboratory, California Institute of Technology, pp. 24–47 {{citation}}: |volume= has extra text (help)
  • Lomnitz, Cinna; Lomnitz, Larissa (12 January 1978), "Tangshan 1976: a case history in earthquake prediction", Nature, 271: 109–111, doi:10.1038/271109a0.
  • Malcolm, Andrew H. (2 June 1977), "Chinese Disclose That 1976 Quake Was Deadliest in Four Centuries", New York Times, p. 1.
  • Mao, Yingsheng; Liang, ZhiJiang; Cui, Cui (2002), "Lightly Damaged Bridges in the High Intensity Earthquake Zone", in Housner, George W.; He, Duxin (eds.), Report On The Great Tangshan Earthquake of 1976, vol. Volume 3, Pasadena, California: Earthquake Engineering Research Laboratory, California Institute of Technology, pp. 231–242 {{citation}}: |volume= has extra text (help)
  • Palmer, James (2012), Heaven Cracks, Earth Shakes: The Tangshan Earthquake and the Death of Mao's China, Basic Books, ISBN 978-0-465-01478-1.
  • Spence, Jonathan (1991), The Search for Modern China, W. W. Norton & Company, ISBN 0-393-30780-8.
  • Stoltman, Joseph P.; Lidstone, John; Dechano, M. Lisa. (2004), International Perspectives On Natural Disasters, Springer Publishing, ISBN 1-4020-2850-4.

Further reading

External links

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