Human Induced Earthquakes: Section 2 | Reservoir Induced Seismicity


Anthropogenic Earthquake Week at CatMap

Reservoir Induced Seismicity: Hydroelectric Projects Have Been Causing Serious Earthquakes Since 1934

In Section 1, we discussed induced seismicity caused by injecting or removing large quantities of liquids from underground geological structures. The effects of these anthropogenic 1earthquakes range from inconvenience to property damage to death on a large scale.Humans also cause earthquakes when they create new water reservoirs behind large dams to create hydroelectric power. This phenomenon may be a surprise to you, but is not a surprise to the people who build them. There is even an engineering term for earthquakes caused by hydroelectric dams: “Reservoir Induced Seismicity” or RIS (alternatively RTS – Reservoir Triggered Seismicity). It isn’t a major scientific challenge to comprehend why reservoirs cause quakes. Water is an extremely heavy element weighing in at 62.4 lbs a cubic foot. When a huge mass of H2O is introduced into any site it did not occupy previously, it places enormous stress on the underlying rock formations.The first documented RIS quake took place during the Great Depression as the newly constructed Hoover Dam filled up Lake Mead in southern Nevada. The Hoover Dam structure itself only weighs about 6.6 million tons, but the reservoir behind it holds back 9.6 trillion gallons of water. Each gallon weighs 8.35 lb. (about 3.79 kg), resulting in 100 trillion pounds of new stress on the rock formations. Hundreds of local earthquakes – some up to magnitude 5.0 – unsettled the region around the dam beginning in 1934 and lasting a decade. No one got too riled up about that one, though, what with it being the Depression and all. Jobs creation has historically caused people to accept inconvenience, intimidation and occasionally even death. The Hoover Dam earthquake swarms eventually subsided.

Modern dams continue to get larger and so do the seismic problems that go with them. Today there are any number of other examples of megadams causing earthquakes and mudslides, along with unimaginable ecological and human misery. The Zipingpu Dam in China is widely believed to have caused the deadly Sichuan quake in 2008, a 8.0 magnitude temblor that killed upwards of 90,000 people, ranking in the top twenty most deadly quakes of all time. The dam was built 1,6500 (500 meters) from the earthquake’s fault line; the pressure of the water in the dam most likely oscillated the fault, leading to stress failure. A research paper by a group of Chinese scientists concluded that the weight of collected water clearly affected seismic activity, but the Chinese government said no, that was not at all the case. We are not the first to note that scientific results are inevitably driven by economic interest. Those scientists are now working the rice fields.2

Sichuan Earthquake 2008
Everyone believes the Zipingpu Dam in China caused the 8.0 Sichuan quake except the authorities responsible for building it.

The Koyna Dam is the largest hydroelectric dam in India. In 1967, it managed to withstand the Koynanagar earthquake, a 7.9 bad boy that wreaked death and devastation in the area. That quake was also widely believed to have been caused by the reservoir. Prior to the quake, the Koyna area was considered aseismic, which is why the quake took everyone by surprise. The dam developed cracks after that quake, but has been repaired to the satisfaction of the authorities. So don’t worry if you plan to visit Koyna.

The Koyna quakes actually began in 1962, when Shivajisagar Lake began to fill. In addition to the big one, there were also at least 22 quakes larger than 5.0 magnitude and 200 around 4.0. In 1993, the construction of another reservoir at Warna, India triggered new quakes. Seismic activity continues, with frequency increases during the monsoon season.

The Grand Mofo of all the giant hydro projects is the somewhat infamous Three Gorges Dam on the once scenic Yangtze River Gorge in China. This disaster in the making is perhaps the most humanly abusive “public” project in a long series of Chinese problem solving ideas. A 2011 Chinese study showed the newly filled dam caused upwards of 3,000 earthquakes, a thirty-fold increase from before construction began.

Now 600 feet tall, the world’s largest hydroelectric project was conceived in 1992 amidst the warnings of environmentalists and geologists and completed in 2012. Landslides have increased each year, with literally thousands of unhappy geological events recorded. The most significant was the devastating 8.0 magnitude quake in Sichuan Province May 2008, which left at least 87,000 people dead. As a result of the original quake and a series of powerful aftershocks, several rivers were blocked by large landslides, which resulted in the formation of “quake lakes” behind the blockages.

One landslide created a 65 foot wave that killed 14 people. The weight of the lake itself causes an increasingly likelihood of more earthquakes, exacerbated by seasonal variations in lake level. In a worst case scenario, a seismic event could damage the dam itself. That would be a big “downstream” problem as the business types like to say. The water behind the Three Gorges Dam weighs about a quadrillion pounds.

In November 2012, an earthquake measuring 3.2 on the Richter scale hit the same region, but the authorities announced that it could not have been caused by the dam.

In 2012, we also have the Song Tranh 2 Dam – Vietnam’s largest hydro project and also built on a fault – which began causing earthquake swarms shortly after construction.

Similar to the logic driving deep wastewater storage and drilling induced quakes, the calculation is that the economic benefits of huge dams outweigh physical earthquake damage, massive and often tragic human displacement, environmental devastation and other downsides. We do know for certain that the benefits to the controlling industrial interests are immense, because in almost every case, they don’t live near the dam. Huge hydroelectric projects are also underway in Brazil and Africa while China gears up to construct three more monsters.

Section 2 Notes:
1. Anthropogenic means “caused by humans”. It is term used to characterize the current global warming situation by those who believe humans have something to do with the unusual weather we been having.
2. We don’t know that they are working in rice fields. However, in China and the United States, scientists who disapprove of projects backed by authorities find themselves discredited or marginalized.

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