Wednesday, January 04, 2012

How Humans Cause (and Prevent) Earthquakes

The best-known case is the earthquake caused by the Zipingpu Dam, in China’s Sichuan province, in 2008. Zipingpu held 42.3 billion cubic feet of water, the weight of which precipitated what Klose says is the largest human-triggered earthquake to date: a 7.9-magnitude quake that killed nearly 80,000 people. Klose estimates that Zipingpu, with nearly 320 million tons of water pressing down on a fault line, contributed enough stress to trigger the quake through a process called impoundment. “If you push your finger on top of a paper plate, the plate will bend,” he says. “That same effect works on all the tectonic plates on the Earth’s crust.” The quake occurred two years after the dam’s completion, and its epicenter was a mere three miles from the structure.

Authorities in Basel, Switzerland, shut down the city’s geothermal plant after a 3.4 quake in 2006. Tapping geothermal energy involves boring into rock miles beneath the Earth’s crust in search of steam as a source of energy. Engineers in areas without much water, such as Basel, sometimes create boreholes by way of hydraulic fracturing, or “fracking,” which involves forcefully injecting water to create fissures. Fracking can generate small tremors, but the real damage may happen as excess liquid pools in the cracks between rocks, making them less stable. Although dams have caused some 76 earthquakes, mining is responsible for at least 137 earthquakes, over half the number of man-made quakes to date.

In 1989 a 5.6-magnitude earthquake hit Newcastle, Australia, the direct result of coal mining. Extracting millions of tons of coal added stress to the fault lines, but the real danger resulted from the water that was extracted during mining. For each ton of coal produced, Klose estimates, 4.3 times as much water was pumped out of the ground, a necessary step to prevent flooding inside the mine. But removing so much water dramatically altered the stability of the earth surrounding the mine. Klose says the earthquake caused $3.5 billion in damage—an amount that nearly equaled the profit of all the coal produced by the mine over its 200-year history. _PopSci
More here

Other human-caused micro-quakes have occurred via deep well injection of fluids, and by experimental deep hydraulic fracturing into crystalline rock (such as granite) near faults. It should be noted that shale fracturing -- such as is done for oil & gas production -- has not produced a causal link to earthquakes.

The recent small quakes in the Youngstown, Ohio area are associated with deep well injection of waste fluids -- a completely different process from shale fracturing.

Unfortunately, a large part of the news media has reported the quakes as having been caused by shale fracturing -- which is not the case. This type of skanky behaviour by news media is nothing new, but one has to wonder whether it is caused by ignorance or by willful deception.

We expect the faux environmental and green sites to misreport such events -- out of both ignorance and willful deception, depending upon the outlet. But in the case of the Ohio micro-quakes, normally careful sites such as,, and other mainstream outlets produced news copy that was not fit for a third grade newsletter, due to the inaccuracies. This is a troubling trend that should be watched very carefully.

It has been shown for decades that deep fluid injection into the crust can induce micro-quakes, if it takes place near known and discovered faults. And of all energy-related drilling, the type most closely associated with inducing micro-quakes is geothermal -- both enhanced and the geyser type. Deep CO2 injection is likewise liable to induce micro-quakes. Shale fracturing is probably the least likely cause of micro-quakes due to the more shallow nature and due to the type of rock involved.

But if one wishes to be absolutely sure that one is not performing shale fracturing near a fault zone, a thorough seismic survey (for about $10 million) can be done prior to any drilling. Clearly a less expensive method of reassuring the panicky public, skankstream media, and less than honest environmental media is needed.

Scientific research is the best antidote to the type of superstitions being purveyed by the modern skankstream.

Some European experience:
The data generally support the view that injection in sedimentary rocks tends to be less seismogenic than in crystalline rocks. In both cases, the presence of faults near the wells that allow pressures to penetrate significant distances vertically and laterally can be expected to increase the risk of producing felt events. All cases of injection into crystalline rocks produce seismic events, albeit usually of non-damaging magnitudes, and all crystalline rock masses were found to be critically stressed, regardless of the strength of their seismogenic responses to injection. Thus, these data suggest that criticality of stress, whilst a necessary condition for producing earthquakes that would disturb (or be felt by) the local population, is not a sufficient condition. The data considered here are not fully consistent with the concept that injection into deeper crystalline formations tends to produce larger magnitude events. The data are too few to evaluate the combined effect of depth and injected fluid volume on the size of the largest events. Injection at sites with low natural seismicity, defined by the expectation that the local peak ground acceleration has less than a 10% chance of exceeding 0.07 g in 50 years, has not produced felt events. _Geothermics

Enhanced geothermal drilling is a far greater micro-earthquake hazard than is any drilling or fracturing in porous shale for oil & gas. But even so, it is best to avoid overreacting to the risk, but rather to plan deep drilling and hydraulic fracturing of crystalline rock very carefully, to minimise risks.
The risk of overreaction to the risks inherent in deep geothermal projects is very real. The establishment of an overly harsh regulatory framework would penalize the geothermal industry in comparison to other energy sectors that carry a recognized risk of inducing seismicity, such as gas extraction or coal mining.

From their outset, EGS projects need to be thought of both as pilot projects with scientific unknowns and as commercial ventures with technological and financial risks. Companies need to have allocated enough of their budget to scientific investigations not directly related to the exploitation of heat. Local authorities need to avoid being enticed by the promises of alternative energy, and to remember to ask the right questions. Risk evaluations need to be done before — not after — these projects begin. _Nature
In such cases where the risks are small but clear, appropriate care must be used in conjunction with any deep geothermal drilling, or deep well injections -- particularly near fault zones.

But the risks of shale drilling and fracturing are completely different -- and orders of magnitude smaller -- than the risks of drilling and fracturing crystalline rock such as granite. If regulatory agencies rush in to ban economically important procedures which have been demonstrated to be safe over decades of experience and geological testing, they will be doing a grave disservice to their constituents.

Labels: , , ,


Post a Comment

Subscribe to Post Comments [Atom]

<< Home

Newer Posts Older Posts