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BOX 1.3
Statement of Task

The study will focus on areas of interest related to CCS, enhanced geothermal systems, production from shale gas, and EOR, and will

1. summarize the current state-of-the-art knowledge on the possible scale, scope, and consequences of seismicity induced during the injection of fluids related to energy production, including lessons learned from other causes of induced seismicity;

2. identify gaps in knowledge and the research needed to advance the understanding of induced seismicity, its causes, effects, and associated risks;

3. identify gaps and deficiencies in current hazard assessment methodologies for induced seismicity and research needed to close those gaps; and

4. identify and assess options for interim steps toward best practices, pending resolution of key outstanding research questions.

we, as humans, perceive or feel and the extent of damage to structures and facilities. The intensity of an earthquake depends on factors such as distance from the earthquake source and local geologic conditions, as well as earthquake magnitude. Throughout this work we refer to earthquake magnitudes using the moment-magnitude scale (Hanks and Kanamori, 1979), which is a scale preferred by seismologists because it is theoretically related to the amount of energy released by the Earth’s crust. The common symbol used to indicate moment magnitude is M.9

The earthquake magnitude scale spans a truly immense range of energy releases. For example, an earthquake of M 8 does not represent energy release that is four times greater than an earthquake of M 2; rather, an M 8 releases 792 million times greater energy than an M 2. For tectonic (“natural”) earthquakes, magnitude is also closely tied to the earthquake rupture area, which is defined as the surface area of the fault affected by sudden slip during an earthquake. A great earthquake of M 8 typically has a fault-surface rupture area of 5,000 to 10,000 km2 (equivalent to ~1,931 to 3,861 square miles or about the size of Delaware,


9 The moment magnitude scale, designated M, is the conventional scale now in use worldwide because it is related to the energy or “work” done by the Earth’s crust in creating the earthquake. An earthquake magnitude scale was first published by Richter (1936) and was based on the amplitudes of ground motions recorded on standard seismometers in Southern California. The desire was to assign a numerical magnitude value to earthquakes that was logarithmically proportional to the amount of energy released in the Earth’s crust, although it was recognized by Richter that the available data were inadequate for developing a direct correlation with energy. The original scale for Southern California achieved widespread use, was designated “Richter” or local magnitude, and was adapted for other areas with modifications to account for regional differences in earthquake wave attenuation. The moment magnitude has the ability to represent the energy released by very large earthquakes. Moment magnitude, where available, has been used throughout the report.

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