Measurement of the duration of high-frequency energy radiation and its application to determination of the magnitudes of large shallow earthquakes

We have developed an algorithm to measure the duration of high-frequency energy radiation by processing the first arriving P -waves and then applied it to analyses of 69 large shallow earthquakes that occurred between 1995 and 2006. We compared our estimates to time differences between centroid and origin times in the Harvard CMT catalog and found that there was a good correlation between them, thereby suggesting that the measured durations are good estimates of source durations. We show that it is possible to determine magnitudes consistent with moment magnitudes in the Harvard CMT catalog using the durations of high-frequency energy radiation and maximum displacement amplitudes of the first arriving P -waves.