(November 21, 2011) Matt Ridley, writing about dams and induced seismicity in the Wall Street Journal, cites Probe International’s reports on the consequences of building the Three Gorges Dam: the Yangtze is drying up downstream, and seismic activity has increased 30-fold.
Earthquakes are natural disasters. However much culpability there is afterward about the building standards that may have worsened the death toll or the response of the emergency authorities, nobody is to blame for the actual shock.
At least, not normally. An exception is the phenomenon of “induced seismicity,” whereby human activity such as geothermal energy projects, mining, gas drilling or the filling of reservoirs apparently sets off swarms of very small earthquakes where there are susceptible geological faults and in certain kinds of underlying rock.
A recent report from the U.S. Geological Survey concludes, for example, that a nearby shale gas well probably caused a swarm of 43 very small earthquakes (largest magnitude, 2.8) in Garvin County, Okla., last January. A few hours before the quakes began, the well had ceased hydraulic fracturing or “fracking”: that is, injecting high-pressure water into the ground to crack deep rocks.
Two years ago the Swiss city of Basel, which was destroyed by an earthquake in 1356, stopped a project to tap heat from underground rocks after some small quakes culminated in one big enough (2.9 magnitude) to meet the previously agreed-upon standard for reviewing the project.
That building dams to impound millions of tons of water causes small earthquakes is not in doubt. Many cases from all over the world are now known. That it causes large and dangerous quakes is more uncertain. In India in 1967, the filling of a dam was suspected of causing a 6.3-magnitude quake that killed 180 people.
Worryingly, a new scientific paper asserts confidently that a big, lethal earthquake—the 7.9-magnitude quake in China’s Sichuan province in May 2008, which left 90,000 people dead or missing—was “likely” caused by the filling of a new dam a few miles away. The paper, called “Evidence for Surface Loading as Trigger Mechanism of the 2008 Wenchuan Earthquake,” was published by Christian Klose of Columbia University in the journal Environmental Earth Science.
Using mathematical models of the faults beneath the area, he argues that the impounding of at least 350 million tons of water behind the Zipingpu dam, which began in 2005, probably “advanced the clock of the main shock by up to six decades.” That is to say, the fault was getting ready to fail, but the weight of the water was the straw that broke its back prematurely.
This is yet another black mark against dams, to add to the loss of free-flowing streams and their landscapes, and other problems. As reported by the Canadian pressure group Probe International, Chinese scientists have concluded that filling the Three Gorges Dam on the Yangtze has caused the river to dry up downstream and has increased seismic activity 30-fold, risking dangerous landslides. Though they are needed for water storage for cities, dams are among the most environmentally destructive things that we create. “Clean energy” they are not.
Whatever the rights and wrongs of dam building, induced seismicity is part of a trend affecting human culpability in general. Gradually, over the years, people have taken on more responsibility for what goes wrong in the world. Acts of God have become acts of man. Five hundred years ago, even with unlimited money and power, there would have been little a ruler could do to prevent plague, famine, flood or misery. Now almost every death from infectious disease, hunger or weather, wherever it happens in the world, is in theory preventable.
With knowledge comes responsibility. The destruction of a city by an asteroid that we fail to divert, or the death of a child in Africa to whom we fail to get a dose of oral-rehydration therapy, is on our conscience now as never before. If even some earthquakes might be our fault, it is responsibility we should welcome, because it is better to have rows about who caused or failed to prevent a disaster than to live in a world where disasters are inevitable.
Read the original article on the Wall Street Journal.
Leave a Reply