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

Tatsuhiko Hara

doi:10.1186/bf03353099

Abstract

Abstract 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.

Highlights

It is important to rapidly determine the locations and sizes of earthquakes in order to estimate possible damage, issue tsunami early warnings, and deploy countermeasures to mitigate earthquake disasters
We have developed a technique to determine the magnitudes of large earthquakes rapidly
In order to estimate seismic moments, we used the formula of Ekstrom et al (1992): τ = 2 × 10−8 × Mo1/3, where τ and Mo are the duration over which 95% of the seismic moment is released and seismic mowhere M is an earthquake magnitude, A is the maximum displacement during the estimated duration of highfrequency energy radiation from the arrival time of a Pwave, is the epicentral distance, t is the estimated duration of high-frequency energy radiation

Summary

Introduction

It is important to rapidly determine the locations and sizes of earthquakes in order to estimate possible damage, issue tsunami early warnings, and deploy countermeasures to mitigate earthquake disasters. The determination of the magnitude of an earthquake is one of routine seismological data analyses, for the case of the 26 December 2004 Sumatra earthquake, it took more than 4 h for an estimate of Mw=8.9 to be issued by the Harvard University (Park et al, 2005a). This difficulty in being able to rapidly determine the magnitudes of large earthquakes has led some seismologists to propose new techniques to the rapid quantification of large earthquakes. We measure the duration of high-frequency energy radiation by processing of the first arriving P-waves; we determine the magnitudes using measured durations and maximum displacement amplitudes

Measurement of the Duration of HighFrequency Energy Radiation

Findings

Discussion