2021 Luxian earthquake

The 2021 Luxian earthquake was a damaging seismic event occurring in the early hours of September 16 at 04:33 China Standard Time.[2] The surface wave magnitude (Ms ) 6.0 or moment magnitude (Mw ) 5.4 earthquake struck at a shallow depth of 7.5 km and severe shaking in an area of 4,000 square kilometers was assigned a maximum intensity of VIII on the China seismic intensity scale.[3] Three people were killed and 146 injured when the earthquake struck Lu County, Luzhou, Sichuan Province. At least 36,800 buildings were affected, 7,800 of them seriously damaged or completely destroyed, causing about a quarter of a billion dollars worth of damage.

2021 Luxian earthquake
2021 Luxian earthquake is located in Sichuan
2021 Luxian earthquake
2021 Luxian earthquake is located in China
2021 Luxian earthquake
UTC time2021-09-15 20:33:31
ISC event621079013
USGS-ANSSComCat
Local date16 September 2021
Local time04:33 (CST)
Magnitude5.4 Mw
6.0 Ms
Depth7.5 km (4.7 mi)
Epicenter29.194°N 105.374°E / 29.194; 105.374
TypeReverse fault
Areas affectedLu County, Sichuan, China
Total damage$250 million USD[1]
Max. intensityCSIS VIII
Casualties3 dead, 146 injured

Tectonic setting
A map of the India-Asia deformation zone with active faults in the region.

The active plate tectonics of the Sichuan Basin is dominated by the north–south continental collision of the Indian Plate and Eurasian Plate. As the Indian Plate collides along a convergent plate boundary known as the Main Himalayan Thrust, it being of continental crust does not subduct, rather it plows into the Eurasian Plate. This process severely deforms the Eurasian Plate, uplifting the crust, forming the Tibetan Plateau. The force of the Indian Plate converging pushes the Tibetan Plateau east, towards the Sichuan Basin, forming another zone of collision. This collision and resulting crustal deformation of the Eurasian Plate is accommodated by the Xianshuihe fault system, Kunlun Fault, Altyn Tagh fault, and Longmenshan Fault. The presence of active faults in Sichuan makes the region vulnerable to damaging earthquakes. The deadly 2008 Sichuan earthquake occurred due to a thrust fault rupture on the Longmenshan Fault.[4]

Earthquake

The China Earthquake Networks Center placed the epicenter of the quake in Lu County, Sichuan and recorded its magnitude at Ms  6.0. Meanwhile, the China Earthquake Administration (CEA) placed the Mw  magnitude at 5.3. The U.S. Geological Survey (USGS) recorded the event at Mw  5.4 or mb 5.9.[2] A maximum seismic intensity of VIII was assigned Sichuan Earthquake Administration and CEA. It was felt with weaker intensities by residents as far as Chengdu.[5]

The focal mechanism solution by both theUSGS and CEA indicated shallow reverse faulting at a depth of 7.5 or 6 km.[6] A fault plane with a northwest–southeast striking structure due to northeast–southwest compression within the Eurasian Plate. An official at the Sichuan Seismological Station said the earthquake did not occur on the same fault as the 2008 event, adding that it was on the Huayingshan Fault Zone.[7] The Huayingshan Fault Zone is much longer than the Longmenshan Fault, at 600 km in length, and is one of the largest faults in the Sichuan Basin. The fault has a northeast strike and dip at angles of 30° to 70°. The fault has a slip sense of sinistral strike-slip and thrust.[8]

Impact

The earthquake caused the collapse of over 1,400 houses, severely damaged 6,400 houses, and slightly damaged 29,000 houses. The majority of the homes damaged were old and of poor construction quality. Newer buildings withstood the tremor better as they were improved after the 2008 Sichuan earthquake, which killed nearly 90,000 and left over 18,000 missing.[9] The quake damaged a warehouse in Lu County which led to the loss of 150 tons of liquor.[10]

Power outages were caused by the earthquake which disrupted power supplies and affected at least 20,000 homes. Telecommunication services ceased due to damage at 106 facilities and broken cables.[11][12] Three high-speed rail services were temporarily suspended at Lu County as a result.[13] The collapse of many homes in Lu County severely damaged a number of gas pipelines, affecting 678 families.[11] Damage was reported at 42 reserviors, 10 embankments, 32 irrigation projects, and nine water supply centers.[14]

A small landslide occurred at Yuchan Mountain, partially burying the road along its slopes. Officials at the Chengdu University of Technology said there is a low risk of landslides occurring in the affected areas.[15]

Casualties

The collapse of prefabricated buildings resulted in the deaths of two individuals. The first victim was an elderly man in his 70s who died after bricks fell onto him in his home. Another woman died when the prefabricated panels of her home fell on her.[16] A third death was confirmed the following day as a woman in her 70s.[17] Another 146 people were treated for injuries, at least three of them were in critical condition.[16] Over 70,000 people were evacuated for medical treatment or temporary housing.[18]

Response

Within five seconds of detection by seismic instruments, the earthquake early warning system issued a warning via radio, television, and other means of broadcast. Apps like Sina Weibo and Alipay also provided advanced warning to users several seconds before shaking could be felt.[19]

More than 7,400 armed police and firefighters, 304 vehicles, and 95 rescue equipment such as patrol boats, and excavators were dispatched by Lu County to carry out rescue and relief works. The Luxian No.2 Middle School and Jiuquhe Park were used to temporarily facilitate the relocation of affected residents. Some 2,500 tents, 20,700 folding beds, 20,600 blankets and over 10,000 household items were provided to survivors. The Sichuan government 50 million yuan in allocation to disaster relief efforts, temporary shelter, patient transportation and resettlement and medical treatment.[20]

See also

References
  1. National Geophysical Data Center / World Data Service (NGDC/WDS) (2021). "Significant Earthquake Database" (Data Set). National Geophysical Data Center, NOAA. doi:10.7289/V5TD9V7K. {{cite journal}}: Cite journal requires |journal= (help)
  2. "M 5.4 - 52 km SE of Neijiang, China". earthquake.usgs.gov. U.S. Geological Survey. Retrieved 25 September 2021.
  3. Liu Debin, ed. (16 September 2021). "四川泸州市泸县发生6.0级地震，震源深度10千米" [An earthquake with a magnitude of 6.0 occurred in Lu County, Luzhou City, Sichuan Province, with a focal depth of 10 kilometers]. Sina Corporation. Retrieved 25 September 2021.
  4. Becky Oskin (21 April 2013). "What Caused The Deadly China Earthquake?". Live Science. Retrieved 25 September 2021.
  5. "四川泸县发生6.0级地震" [A 6.0-magnitude earthquake occurred in Luxian, Sichuan]. Sichuan Earthquake Administration. 16 September 2021. Retrieved 25 September 2021.
  6. "2021年9月16日四川泸州市泸县6.0级地震科技支撑简报" [Bulletin of Science and Technology Support for the 6.0-magnitude Earthquake in Lu County, Luzhou City, Sichuan on September 16, 2021]. China Earthquake Administration. 17 September 2021. Archived from the original on 17 September 2021. Retrieved 25 September 2021.
  7. Huang, Zhiling (17 September 2021). "Earthquake in Sichuan leaves 3 dead, sees more than 70,000 evacuated". China Daily. Retrieved 25 September 2021.
  8. Zheming Shi; Guangcai Wang (2014). "Sustained groundwater level changes and permeability variation in a fault zone following the 12 May 2008, Mw 7.9 Wenchuan earthquake" (PDF). Hydrological Processes. 29 (12): 2659–2667. doi:10.1002/hyp.10387. S2CID 140148606.
  9. Gaojia GJ. "The 6.0-magnitude earthquake in Luxian County, Sichuan has caused 3 deaths and 100 injuries, and 121,000 people were affected" (in Chinese). Interface News. Retrieved 25 September 2021.
  10. Zhang Yu, ed. (17 September 2021). ""150 tons of liquor leaked during the Luxian earthquake": collected and sent to the sewage treatment plant" (in Chinese). Sina Corporation. Retrieved 25 September 2021.
  11. "泸县地震最新伤亡情况：3人死亡，146人受伤" [The latest casualties in the Luxian earthquake: 3 dead and 146 injured]. Sina Corporation. The Paper. 17 September 2021. Retrieved 25 September 2021.
  12. "China Focus: 3 dead, 88 injured in 6.0-magnitude Sichuan earthquake". Xinhuanet. Xinhua News Agency. 16 September 2021. Retrieved 25 September 2021.
  13. Zhu Jiabei, ed. (16 September 2021). "四川泸县地震已致3死3重伤85轻伤 72755人被紧急转移" [Sichuan Luxian earthquake has caused 3 deaths, 3 severe injuries, 85 minor injuries, 72,755 people were urgently transferred]. China Central Television. Retrieved 25 September 2021.
  14. Yang Ni (17 September 2021). Wang Shanshan (ed.). "四川泸县地震造成多处水利工程不同程度受损 已建立台账抓紧处置" [The earthquake in Luxian County, Sichuan Province caused damage to many water conservancy projects to varying degrees. Accounts have been established and deal with it quickly]. Sina Corporation. Beijing Today. Retrieved 25 September 2021.
  15. "成理地灾防治国家重点实验室：泸县地震震区发生同震滑坡的概率较低" [State Key Laboratory of Earth Disaster Prevention: The probability of co-seismic landslides in the earthquake-stricken area of Luxian County is low]. qq.com. Tencent. 16 September 2021. Retrieved 25 September 2021.
  16. 澎湃新闻 (2021-09-17). "泸县地震致数万房屋受损：近十万人转移，当地开展危房排查" [Tens of thousands of houses were damaged by the earthquake in Luxian County: Nearly 100,000 people were transferred, and local dilapidated houses were investigated] (in Simplified Chinese). 新浪新闻. Archived from the original on 2021-09-17. Retrieved 2021-09-17.
  17. "老伴讲述泸县地震爱人遇难：她刚过70大寿" [My wife tells about the death of her lover in the earthquake in Luxian County: She just passed her 70th birthday]. Sina Corporation. 17 September 2021. Retrieved 25 September 2021.
  18. "中国四川泸县6级地震至少3人丧生 紧急转移逾7万人" [At least 3 people were killed in an earthquake of magnitude 6 in Luxian County, Sichuan, China and more than 70,000 people were evacuated]. BBC News. 16 September 2021. Retrieved 26 September 2021.
  19. "中国地震预警网震后5秒发布四川泸县6.0级地震预警警报" [China Earthquake Warning Network issued a 6.0 earthquake warning in Luxian County, Sichuan Province 5 seconds after the earthquake] (in Simplified Chinese). China News Service. 2021-09-16. Archived from the original on 2021-09-17. Retrieved 2021-09-25.
  20. Li Na, ed. (17 September 2021). "The latest casualties in the Luxian earthquake: 3 dead and 146 injured" (in Chinese). Sina Corporation. Retrieved 25 September 2021.
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