Expert denies links between Sichuan quake and Three Gorges Dam

Photo taken on August 11, 2017 shows tents at a temporary shelter in Zhangzha Village of Zhangzha Town in Jiuzhaigou County, southwest China's Sichuan Province. Temporary shelters have been established in Jiuzhaigou after a 7.0-magnitude earthquake strikes Jiuzhaigou County on August 8, 2017. Quake-affected people receive relief supplies and start their lives in tents. [Photo: Xinhua/Xue Yubin]

An expert from the Chinese Academy of Engineering (CAE) on Friday refuted some online speculation that the Three Gorges Dam could have been related to the 7.0-magnitude quake that hit southwest China's Sichuan Province Tuesday.

The epicenter of the quake was located near three fault zones, where frequent seismic activity makes the area earthquake-prone, according to Chen Houqun, an academician with the CAE.

Chen attributed the quake to the Indochina block's northward movement.

"The Three Gorges Dam and its major reservoirs were built along the middle and lower reaches of the Yangtze River, which are not in the same geologic structural unit as the fault zones that caused the Jiuzhaigou earthquake," said Chen.

"The dam has no connection with the fault zones that caused the quake in terms of geologic structure," he added.

Chen also refuted the claim that the quake was reservoir-triggered, or a reservoir-induced seismic activity (RIS).

"A lot of research was done before the construction of the Three Gorges Dam to evaluate possibilities of RIS," said Chen. "The dam was built in a geologically stable area."

Of all the existing reservoirs in the world, only four have triggered earthquakes that are above 6.0 in magnitude, according to Chen.

An expert from the China Earthquake Networks Center (CENC) also clarified matters concerning the frequency of China's earthquakes in an interview with Xinhua.

"It's not rare to see a 7.0-magnitude earthquake in China," said Liu Jie, deputy head of the CENC. "The frequency is twice in three years on average."

It has been 24 months since the last 7.0-magnitude earthquake struck China, and eight months since the last 6.0-magnitude earthquake, according to Liu.

"China is not in a seismically active period currently," Liu told Xinhua. 

Two strong earthquakes hit China on Tuesday and Wednesday, with one measuring 7.0 magnitude in Jiuzhaigou, Sichuan Province, and the other measuring 6.6 magnitude in Bortala Mongolian Autonomous Prefecture in Xinjiang.

The Jiuzhaigou earthquake was fatal, leaving at least 24 people dead and 493 injured.