Estimating Radiated Seismic Energy over 17 Orders of Magnitude

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This research investigated the scaling of radiated seismic energy as a function of earthquake size. Radiated energy has only recently been studied and previous reliable estimates are few. However, new instrumentation, such as K-Net in Japan allows more reliable estimates. So this research provides new results about the estimates of radiated energy of earthquakes.There were 3 main studies.1. Energy estimates for shallow (0-50 km) moderate (M4-6) earthquakes in Japan. We analyzed 115 earthquakes. To make reliable estimates of energy, station corrections for several hundred K-Net sites were determined. We found that the energy is approximately proportional to the moment. However, since the magnitude range is limited, it is difficult to see any trend from just these data. These results are similar to results for shallow earthquakes in California.2. We compared of energy estimates of shallow and deep earthquakes. 32 shallow and 37 deep events from Hokkaido and Tohoku were analyzed. To make reliable energy estimates, site corrections and path attenuation were determined for this data set. When comparing energies of shallow and deep earthquakes, the shallow earthquakes show an increase of energy to moment ratio, as a function of earthquake size. While for deep earthquakes the energy to moment ratio is constant as a function of earthquake size.3. We did some detailed work on aftershocks of the 1994 Northridge, California earthquake. This works confirms that for shallow earthquakes in California, the ratio of energy to moment increases as a function of earthquake size.