21
Jun
12

whole lot of shaking

Post from Harry Hutchinson:

Harry Hutchinson

A few weeks ago I found myself in the land of moose, Moosehead, and the Thousand Islands in Upstate New York. So I had to take the one-hour boat ride. I learned that there are indeed well more than a thousand islands in the St. Lawrence River, and they are the remains of very old mountains that have worn down. These small plots of rock and soil rise a few yards above the water and hold houses that don’t slip off.

It’s amazing how things fit together, that the surface of the Earth is stable enough for that and to support as much life as it does—stable enough for civilization.

It was concern over the effect of advanced civilization on the Earth’s stability that led to a recent study by the National Research Council into induced seismicity—that is, earthquake caused by human activity.

Senator Jeff Bingaman of New Mexico, chair of the Senate Energy and Natural Resources Committee, had asked the Energy Secretary, Stephen Chu, to initiate the study, which would look at the issues of seismic activity attributed to energy technologies, specifically geothermal energy, shale gas, enhanced oil recovery, and carbon capture and storage (or, because it’s a mouthful, CCS).

The NRC has found that human activity has been implicated in detectable movement of the Earth. A preliminary draft of the report is available online at the National Academies Press website.

I think it’s, for the most part, reasonably good news for most current practices. In the executive summary, the authors of the report list what they call “three major findings”:

“(1) the process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events;

“(2) injection for disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation; and

 “(3) CCS, due to the large net volumes of injected fluids, may have potential for inducing larger seismic events.”

 The jury is out on CCS because no one has tried it on a grand scale.

A geothermal project at a steam field called the Geysers in northern California is reported to have had 300 to 400 “felt induced events” each year since 2005. Some of them have hit or exceeded a magnitude of 4.0. The explanation is that “the large temperature difference between the injected fluid and the geothermal reservoir results in significant cooling of the hot subsurface reservoir rocks, causing the rocks to contract, reducing confining pressures and allowing the release of local stresses that results in a significant amount of observed induced seismicity.”

Other geothermal sites are linked to ground movement, too, but to a lesser extent. There are 23 active liquid-dominated sites that are linked to 10 to 40 movements a year.

Just Room Enough

Back at the Thousand Islands, there is one particular house, known as “Just Room Enough,” that illustrates the stability of the ground. The story goes that it was built by the owner of the Waldorf-Astoria, George Boldt, as a summer retreat for his mother-in-law, who had no way to get off the island. He dropped her off in the spring and picked her up in the fall. The foundation comes to the water’s edge. The hotelier built a huge complex, a local landmark known as Boldt Castle, a few hundred yards away across the water.

Maybe his mother-in-law enjoyed extended periods of solitude. Maybe not. Maybe Boldt was hoping the island would shake.

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3 Responses to “whole lot of shaking”


  1. 1 Joanna
    July 11, 2012 at 11:58 am

    very interesting concept. HH.

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The Editor

John G. Falcioni is Editor-in-Chief of Mechanical Engineering magazine, the flagship publication of the American Society of Mechanical Engineers.

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