1973 Luhuo earthquake

Coordinates: 31°23′53″N 100°34′52″E / 31.398°N 100.581°E / 31.398; 100.581
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1973 Luhuo earthquake
1973 Luhuo earthquake is located in Sichuan
1973 Luhuo earthquake
UTC time1973-02-06 10:37:10
ISC event763709
USGS-ANSSComCat
Local dateFebruary 6, 1973
Local time18:37 CST[1]
MagnitudeMs 7.6[2]
Depth11 km (6.8 mi)[3]
Epicenter31°23′53″N 100°34′52″E / 31.398°N 100.581°E / 31.398; 100.581
FaultXianshuihe fault system
TypeStrike-slip
Areas affectedChina
Max. intensityMMI X (Extreme)
LandslidesYes
AftershocksMs  6.3[2]
Casualties2,175–2,204 dead, 2,743 injured

The 1973 Luhuo earthquake struck near the town of

Sichuan Province, China on February 6, 1973, with a magnitude of 7.6 Ms. The earthquake had a maximum intensity of X (Extreme) on the Modified Mercalli intensity scale. It resulted in between 2,175 and 2,204 deaths and a further 2,743 injuries.[4][1] Serious and widespread destruction occurred in Luhuo County
.

Tectonic setting

The tectonic overview of the Tibetan Plateau and Sichuan.

Western

normal faults to break within the thickened crust.[5][6]

Earthquake

A view from above of the Xianshuihe river valley and fault system.

The Xianshuihe fault system is a 1,400 km (870 mi) long active left-lateral strike-slip fault that accommodates the strike-slip motion in the Tibetan Plateau. The fault is one of the largest active intracontinental geological structure in the world. Since 1893, at least 350 km (220 mi) of the fault length has ruptured in large successive earthquakes with magnitudes 6.5 or larger.[7] From 1700 to the present-day, the fault has ruptured its entire length during large earthquakes.[8]

The earthquake measured 7.9 on the Chinese

fault ruptured for a length of 90 km (56 mi), and produced a maximum slip of 3.8 m (12 ft) on the shallow 0–5 km (0.0–3.1 mi) section of the rupture zone.[10][11] Near Dandu Township, an agricultural field was offset by 7.2 m (24 ft), but studies indicated that it was the accumulation of offsets from previous earthquakes as well, including the 1816 event.[12] Surface ruptures were well documented by scientists throughout the 90 km length extending from Renda to Kasu. The southeastern 10 km (6.2 mi) segment of the earthquake rupture overlapped that of the 1923 Renda earthquake,[13] another Ms  7.3 earthquake on the Xianshuihe Fault.[12][10]

The Luhuo segment of the Xianshuihe fault system was also the source of a magnitude 7.5 earthquake in 1816. Field research through trenching at the Luhuo segment however, revealed a record of earthquake history on the fault in the past 3,000 years. The first event identified in the exposed strata layers corresponded to the year 769 BC. Five additional events were also identified to have occurred in the years 318–545 AD, 677–833 AD, and 1008–1444 AD. A recurrence interval has been calculated at between 157 and 1,200 years for the earthquakes from 769 BC–1973 AD.[14]

A Ms  6.3

Geomorphic evidence of the earthquake was well-preserved because the earthquake occurred in mid-winter.[9]

Impact

The earthquake killed between 2,175 and 2,204 people in

Sichuan Province. It also left 43 orphans in the aftermath.[16] It caused extensive destruction along its 90 km (56 mi) of rupture.[9] Nearly homes near or in the path of the rupture were destroyed, amounting to at least 15,700.[17][18] An estimated 2,867 buildings were also heavily damaged. Across two towns in Luhuo County, 4,600 of the 5,000 homes collapsed while another 880 suffered serious damage. A further 90 sustained cracks. China National Highway 318 or the Sichuan-Tibet highway was damaged by rockfalls, landslides and ground cracks at 17 locations. Other roadways, bridges and telecommunication systems were damaged or disrupted as well. Some 40,427 livestock died and 2.01 million kilograms of food were lost.[18] The earthquake triggered between 40 and 50 landslides in the Xianshui River valley.[19] Nearly all recorded landslide features were distributed within a 70 km (43 mi) by 2 km (1.2 mi), or 409 km2 area within the valley.[3] Field surveys observed 137 landslides, all of which lay within the zone of VIII or higher intensity.[3]

Response

A division of the People's Liberation Army was sent to the affected area to assist in rescue and recovery efforts. In the division, at least 668 medical crew from 49 groups attended to injured survivors.[20]

See also

References

  1. ^ a b Utsu, T. "Search Page". Catalog of Damaging Earthquakes in the World (Through 2008). Retrieved June 3, 2010.
  2. ^ a b c Liu Guiping; Fu Zhengxiang. "1973年炉霍大地震（Ms=7.6）最大余震（Ms=6.3）的库仑破裂应力触发" [The Coulomb rupture stress triggering of the largest aftershock (Ms=6.3) of the 1973 Luhuo earthquake (Ms=7.6)]. Earthquake Research in China (in Chinese). 18: 175–182. Retrieved 23 July 2021.
  3. ^
    doi:10.5194/nhess-12-351-2012
    .
  4. doi:10.7289/V5TD9V7K
    . Retrieved 5 January 2023.
  5. S2CID 134590278. Retrieved 19 July 2021.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  6. doi:10.1029/2005JB004120
    .
  7. S2CID 129325246
    .
  8. doi:10.1016/j.epsl.2017.12.045
    .
  9. ^ a b c Clarence R. Allen; Luo Zhuoli; Qian Hong; Wen Xueze; Zhou Huawei; Huang Weishi (1989). "Segmentation and Recent rupture history of the Xianshuihe Fault, Southwestern China". U.S. Geological Survey Open-file Report. Fault segmentation and controls of rupture initiation and termination. (89–315): 10–30. Retrieved 2 July 2021.
  10. ^
    doi:10.14075/j.jgg.2020.08.003
    . Retrieved 2 July 2021.
  11. doi:10.1785/BSSA07306A1585.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  12. ^
    doi:10.1130/0016-7606(1991)103<1178:FSOAHA>2.3.CO;2
    .
  13. ^ "M 7.0 – 184 km NW of Kangding, China". earthquake.usgs.gov. USGS. Retrieved 2 July 2021.
  14. doi:10.3389/feart.2020.00274
    .
  15. ^ "M 5.8 – 227 km NW of Kangding, China". earthquake.usgs.gov. USGS. Retrieved 23 July 2021.
  16. ^ Yang Yanyu, ed. (6 February 2013). "四川炉霍40年从地震废墟上崛起". China News. Retrieved 2 July 2021.
  17. ^ Li Zhongdong (25 February 2019). "鲜水河断裂带，危险与美景并存之地". 163.com. Archived from the original on 9 July 2021. Retrieved 2 July 2021.
  18. ^ a b "1973年炉霍地震". Archived from the original on 2020-02-22. Retrieved 2013-08-13.
  19. ^ "大灾无情！盘点历史上四川发生的10余次7级以上地震". chengdumingxiao.com. 10 August 2017. Retrieved 2 July 2021.
  20. ^ "四川炉霍40年从地震废墟上崛起" (in Chinese). China News Network. 2013. Retrieved 23 July 2021.

External links

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