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Appendix E: Earthquake Size Estimates and Negative Earthquake Magnitudes
Pages 211-216

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From page 211...
... Using borehole seismic arrays located within a few hundred meters of an earthquake source, very small earthquakes can be recorded. These events are smaller than the baseline magnitude of "0" originally designed by Richter, therefore the range of event sizes continues into the negative magnitude range (Figure E.1)
From page 212...
... The seismic moment is a routine measurement describing the strength of an earthquake and is defined as Mo = μSd where μ is the shear modulus, S is the surface area of the fault, and d is the average displacement along the fault. The moment magnitude, Mw, is related to seismic moment by the Hanks and Kanamori (1979)
From page 213...
... This relationship is often referred to as the GutenbergRichter magnitude frequency relationship. Differences in the slope b reveal information about the potential size and expected number of the events in a population of earthquakes.
From page 214...
... The hydraulic fracture microseismic magnitudes are typically very small (less than M 0) , hence the lack of larger microseismic events on this b value example.
From page 215...
... during a hydraulic fracture treatment. The fracturing well is shown by the pink line and is deviated away from a central wellhead location and extends vertically through the reservoir section; the injection location is labeled "Perforations." The data were recorded and analyzed using borehole receivers (marked Geophones)

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