1850 Xichang earthquake

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Coordinates: 27°48′N 102°18′E / 27.8°N 102.3°E / 27.8; 102.3
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1850 Xichang earthquake
1850 Xichang earthquake is located in Sichuan
1850 Xichang earthquake
1850 Xichang earthquake is located in China
1850 Xichang earthquake
Local dateSeptember 12, 1850 (1850-09-12)
MagnitudeMw 7.6–7.9 [1]
Ms 7.7
Epicenter27°48′N 102°18′E / 27.8°N 102.3°E / 27.8; 102.3 [2]
Areas affectedQing dynasty
Max. intensityMMI XI (Extreme) [3]
Casualties20,650+ dead

The 1850 Xichang earthquake rocked

surface wave magnitude
of 7.5–7.7 Ms . An estimated 20,650 people died.

Tectonic setting

The tectonic overview of the Tibetan Plateau and Sichuan.

normal faults to break within the thickened crust.[4][5]

Earthquake

The earthquake occurred as a result of left-lateral

strike-slip faulting at a shallow depth on the highly segmented and complex Xianshuihe fault system. Contemporary paleoseismology studies have identified surface ruptures on the Anninghe and Zemuhe faults; segments of the 1,400-km-long Xianshuihe fault system.[3] The Anninghe Fault is oriented north–south, and is 200-km-long, while the Zemuhe Fault, strikes northwest for 120 km. The two faults have varying slip rates of 3.6–4.0 mm/yr and 3.0–5.0 mm/yr.[1]

Characteristics

The earthquake rupture attracted the attention of seismologists because the Anninghe and Zemuhe faults ruptured during the same event; where a restraining bend could not stop the rupture propagation. Restraining bends or zones of transpression have been previously thought to arrest or cease an earthquake rupture. The restraining bend measuring 30° displayed extensional tectonics was not effective and failed to arrest the rupture.[1]

A maximum coseismic slip of 5–6 meters was measured along a preserved

paleoseismic records. The recurrence interval of large earthquakes on the fault is 1,400 to 1,700 years, with a minimum of 1,000 years.[3]

Rupture on the southern section of the Anninghe Fault also resulted in a zone of high-intensity shaking assigned VII–VIII. The surface offsets on the Anninghe Fault are much smaller, ranging from 1–1.5 meters. Based on the historical documentation of the event and its associated surface ruptures, the total ruptured length on both faults is at least 150 km. A

moment magnitude using the rupture length would indicate a magnitude of Mw  7.6–7.9.[1] The Anninghe Fault previously ruptured in 1536 based on paleoseismic evidence along the fault trace. It had an estimated magnitude of 7.5 and ruptured a 30-km-long section of the fault. A maximum left-lateral offset of 4 meters was estimated.[6]

Impact

In

Huili County, 2,876 residents were killed by collapsing homes. Severe damage occurred in the 14 residential areas in the county.[2] Hundreds died in Qiaojia County. Several deaths were also reported in Puge County, Zhaojue County, Yanyuan County, and Mianning County
.

A massive ground fissure measuring 33 meters long, 10 meters wide, and 17 meters deep opened in the city ground. Trees were uprooted and toppled while roads cracked. Several large landslides occurred near Qiong Lake. Ground failures and fissuring led to water erupting out of the ground. Major liquefaction events such as the ejection of water and sand occurred at Beishan Mountains, Qiong Lake and the Anning River. Villages along the banks of Qiong Lake were flooded.[2]

Legacy

The destruction left by the quake was the third to seriously affect Xichang. The earthquakes in 1536 and 1732 also caused great devastation, killing thousands. The Xichang Earthquake Forest near Xichang serves as a location to remember the victims of the earthquakes. The events were documented and

inscripted onto stele monuments.[7]

See also

References

  1. ^
    doi:10.1785/0120170202
    .
  2. ^ a b c "Significant Earthquake Information". ngdc.noaa.gov. NOAA National Centers for Environmental Information. Retrieved 18 October 2021.
  3. ^
    doi:10.4401/ag-3444
    .
  4. S2CID 134590278
    .
  5. doi:10.1029/2005JB004120
    .
  6. ^
    doi:10.1016/j.jseaes.2009.12.008
    .
  7. ^ Wu Xiaoling (3 April 2020). "200余通石碑 刻下西昌500年地震记忆" [More than 200 stone steles inscribe the memory of the 500-year earthquake in Xichang] (in Chinese). People's Daily. Retrieved 18 October 2021.
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