Geoscience Reference
In-Depth Information
best practices for mitigating induced seismicity risk in Chapter 6. Chapter 7 contains the
report's findings, conclusions, proposed actions, and research recommendations, including
identification of information and knowledge gaps and research and monitoring needs. The
remainder of this chapter briefly reviews earthquakes and their measurement, introduces the
four energy technologies that are the subject of this report, and presents several historical
examples of induced seismic activity related to energy development.
The significance of understanding and mitigating the effects of induced seismicity re-
lated to energy technologies has been recognized by other groups as well, both internation-
ally and domestically. The International Partnership for Geothermal Technology Working
Group on Induced Seismicity 6 under the auspices of the International Energy Agency, for
example, has been addressing the issue as it relates specifically to geothermal energy devel-
opment. International professional societies such as the Society of Petroleum Engineers
and the Society of Exploration Geophysicists are coordinating a public technical workshop
on the topic. 7 Within the United States, government agencies such as the Department of
Energy and U.S. Geological Survey have also been engaged in explicit efforts to understand
and address induced seismicity in technology development. The Environmental Protection
Agency has been facilitating a National Technical Working Group on Injection Induced
Seismicity 8 since mid-2011 and anticipates releasing a report that will contain technical
recommendations directed toward minimizing or managing injection-induced seismicity.
EARTHQUAKES AND THEIR MEASUREMENT
The process of earthquake generation is analogous to a rubber band stretched to the
breaking point that suddenly snaps and releases the energy stored in the elastic band.
Earthquakes result from slip along faults that release tectonic stresses that have grown
high enough to exceed a fault's breaking strength. Strain energy is released by the Earth's
crust during an earthquake in the form of seismic waves, friction on the causative fault,
and, for some earthquakes, crustal elevation changes. Seismic waves can travel great dis-
tances; for large earthquakes they can travel around the globe. Ground motions observed
at any location are a manifestation of these seismic waves. Seismic waves can be measured
in different ways: earthquake magnitude is a measure of the size of an earthquake or the
amount of energy released at the earthquake source, while earthquake intensity is a measure
of the level of ground shaking at a specific location. The distinction between earthquake
magnitude and intensity is important because intensity of ground shaking determines what
6 See http://internationalgeothermal.org/; http://www.iea-gia.org/documents/Switzerland_Inducedseismicity_IPGT_
IEA_201105031.pdf
7 See http://www.spe.org/events/12aden/documents/12ADEN_Brochure.pdf
8 See http://www.gwpc.org/meetings/uic/2012/proceedings/09McKenzie_Susie.pdf; P. Dellinger, presentation to the
committee, September 2011.
 
Search WWH ::




Custom Search