Earthquakes Triggered by Dams
Earthquakes can be induced by dams. Globally, there are over 100 identified cases of earthquakes that scientists believe were triggered by reservoirs (see Gupta 2002). The most serious case may be the 7.9-magnitudeSichuan earthquake in May 2008, which killed an estimated 80,000 people and has been linked to the construction of the Zipingpu Dam.
How Do Dams Trigger Earthquakes?
In a paper prepared for the World Commission on Dams, Dr. V. P Jauhari wrote the following about this phenomenon, known as Reservoir-Induced Seismicity (RIS): "The most widely accepted explanation of how dams cause earthquakes is related to the extra water pressure created in the micro-cracks and fissures in the ground under and near a reservoir. When the pressure of the water in the rocks increases, it acts to lubricate faults which are already under tectonic strain, but are prevented from slipping by the friction of the rock surfaces."
Given that every dam site has unique geological characteristics, it is not possible to accurately predict when and where earthquakes will occur. However, the International Commission on Large Dams recommends that RIS should be considered for reservoirs deeper than 100 meters.
What Are Some Characteristics of RIS?
A leading scholar on this topic, Harsh K. Gupta, summarized his findings on RIS worldwide in 2002:
- Depth of the reservoir is the most important factor, but the volume of water also plays a significant role in triggering earthquakes.
- RIS can be immediately noticed during filling periods of reservoirs.
- RIS can happen immediately after the filling of a reservoir or after a certain time lag.
Many dams are being built in seismically active regions, including the Himalayas, Southwest China, Iran, Turkey, and Chile (see map). International Rivers calls for a moratorium on the construction of high dams in earthquake-prone areas.
Click here for the factsheet on RIS worldwide.
Sichuan Earthquake Damages Dams, May Be Dam-Induced
According to the State-run Xinhua News Agency, the Zipingpu Dam on the Min River experienced "extremely dangerous" cracks, along with a collapsed powerhouse and other associated facilities. Seismologists from China's Earthquake Bureau had warned the government back in 2000 that the project should not be built given its proximity to a major fault line, yet these warnings were ignored. The government later reported that its experts had inspected the dam and declared it safe, although it is not clear exactly how thorough the inspections have been.
Despite the risks posed to millions of inhabitants downstream if a large dam were to break, the Chinese government continues to build scores of dams in the country's most earthquake-prone region, Sichuan and Yunnan Provinces in southwest China. In light of the damages to the dams, mainland experts, environmental groups, and activists have issued an open letter to the authorities. The letter calls for thorough risk assessments of all large hydropower projects in this region before companies are allowed to go forward with construction.
Follow these links for more information about the earthquake and the damage to the Zipingpu and other dams:
- Scientists Link China's Dam to Earthquake, Renewing Debate, The Wall Street Journal
- Dams Could Have Triggered Chinese Earthquake, The Guardian
- China Considers Earthquake Danger of Dams, The Los Angeles Times
- Greens Demand Halt to 'Feverish' Dam Building, Financial Times
- Chinese Environmentalists and Scholars Appeal for Dam Safety Assessments in Geologically Unstable South-West China, First Daily Business
- International Rivers on NPR's “To The Point” about China Quake
- Map of Zipingpu Dam's location in relation to epicenter, BBC News
- Video of Zipingpu Dam inspection, BBC News
Read the Science article about how the Sichuan Earthquake may be linked to the Zipingpu Dam's reservoir. See here for the original article by Christian Klose (2008).