1969 Yangjiang earthquake

Tectonic setting

Guangdong Province lies in a tectonically stable part of China, which has relatively low seismicity. The area forms part of the passive margin between the continental crust of China and the oceanic crust of the northern part of the South China Sea. Within the stable South China Block, there are three zones of higher earthquake activity, one of which is the Southeast China Coast seismic zone running through Guangdong and Fujian Provinces. This zone follows the South China Maritime Fold Belt, which was formed by a subduction event during the Late Jurassic to Early Cretaceous epochs. The area is currently in a compressive stress regime with the maximum horizontal stress orientated northwest–southeast. This results from a combination of the continuing collision between the Indian and Eurasian plates, and the subduction of the Philippine Sea plate.

Earthquake

The earthquake occurred on a steeply-dipping fault striking nearly east–west. The focal mechanism shows mainly dextral (right lateral) strike-slip faulting. The magnitude and number of recorded foreshocks and aftershocks were unusually small, considering the size of the mainshock. This earthquake is the only damaging event in the epicentral area in historical records.

Damage

The epicentral area lay mostly in Yangjiang County, affecting an area measuring 19 km by 10 km, elongated west to east. In the whole county, a total of 10,762 houses were completely destroyed, a further 35,965 were severely damaged and another 90,840 suffered some damage. In Xinyi about 1,200 houses suffered some damage and several were destroyed. The earthquake was also strongly felt in Fengkai, Huaiji, Xinzhong, Deqing, Zhaoqing, Yunan, Zengcheng, Gaohe and Panyu, although there was no serious damage in these areas. Minor damage was also reported in Hong Kong. A report of 3,000 casualties caused by this earthquake is described as "unconfirmed".

References

References

1. (December 1, 2008). "EXPO-CAT Earthquake Catalog". United States Geological Survey.
2. NGDC. "Comments for the Significant Earthquake".
3. (29 March 2010). "Earthquakes with 1,000 or More Deaths since 1900". United States Geological Survey.
4. Megawati, K.. (2004). "Simulation of Distant Earthquakes Affecting Hong Kong". Hong Kong Observatory.
5. Liu, L.. (2001). "Stable Continental Region Earthquakes in South China". Pure and Applied Geophysics.
6. Brantley, B.J.. (1991). "Body-wave waveform constraints on the source parameters of the Yangjiang, China, earthquake of July 25, 1969: A devastating earthquake in a stable continental region". [[Pure and Applied Geophysics]].