1733 Dongchuan earthquake
7.75 Ms earthquake in Yunnan, China
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The 1733 Dongchuan earthquake affected Yunnan in China on August 2. The earthquake, which had an estimated surface-wave magnitude of 7.75, damaged homes across the province. There were dozens of fatalities and more deaths occurred in mines. The earthquake was the result of faulting along the Xiaojiang Fault Zone.
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| Local date | August 2, 1733 |
|---|---|
| Magnitude | Ms 7.75 |
| Epicenter | 26.2°N 103.1°E |
| Areas affected | Yunnan, China |
| Max. intensity | MMI X (Extreme) |
| Casualties | Dozens |
Geology
The Xianshuihe-Xiaojiang Fault is a major sinistral strike-slip fault system in China that runs along the southeastern edge of the Tibetan Plateau. It comprises the Xianshuihe, Anninghe-Zemuhe, Xiaojiang and Daliangshan faults.[1] The Xiaojiang Fault Zone represents the southeastern part of the SichuanâYunnan tectonic block's eastern boundary. The SichuanâYunnan block's southwestern margin is represented by the Jinshajiang and Red River faults. The Xiaojiang Fault Zone is seismically active, having been associated with over ten earthquakes greater than magnitude 6.0 since 1500. This includes a Ms⯠8.0 earthquake in 1833.[2]
Earthquake
The earthquake produced an 82 km (51 mi) surface rupture along the eastern segment of the northern Xiaojiang Fault Zone. It extended northâsouth from Shiliping to Tianba. It was also associated with a depression about 2â3 km (1.2â1.9 mi) long and 200â300 m (660â980 ft) across, bounded by vertical escarpments measuring 5â10 m (16â33 ft). Approximately 9 m (30 ft) of sinistral offset represented the largest strike-slip displacement from the earthquake. Vertical offsets were exclusively recorded south of the Dongchuan basin. Earthquakes of such magnitudes have an average return interval of 2,000 to 3,000 years.[2]
Impact
In Qiaojia, 16 civilians were killed by rockfalls when the town was destroyed. In a military camp, 50 soldiers escaped unhurt while one soldier died from a toppled beam at another campsite. Cui Naiyong, an official in Dongchuan, said about 40 people died in the larger towns of Bigu, Awang and Xiaojiang. He added that most homes, constructed of wood, rarely killed their inhabitants when they collapsed. In the Tangdan mines near Bigu, Cui reported a staggering death toll as each of the several hundred mines contained hundreds and thousands of workers at the time of the earthquake. These mines likely collapsed, killing those inside.[3] Only a handful of people managed to escape from the mines. At Huize, temples and administrative buildings were razed, nearly all fortification along the north and south city walls were destroyed. Forty percent of the battlements on the eastern and western part of the city were also destroyed. Landslides at Mushulang dammed the Yinghe River for three days.[4]