Research on the method to determine the seismic radiated energy and its application in Wenchuan M8. 0 earthquake

The radiated seismic energy is a characteristic quantity about quantification of the source, and its determination is an important fundamental problem in the quantitative study of the earthquake. In this study, based on the point source model, we carried out a research on the determination method of radiated seismic energy, derived the theoretical formulas, and developed a software system for measuring it using far-field vertical P-wave records independently, which can quickly determine the radiated seismic energy of shallow earthquakes of M >= 5. 5 worldwide. The scientificity and accuracy of the method and software are verified by using the example of the Wenchuan M8. 0 earthquake. The results show that : (1) The radiated seismic energy of the Wenchuan earthquake is 2. 84 X 10(16) J, and the distribution of radiated seismic energy of each station has no obvious dependence on the epicenter distance and azimuth, indicating that theoretical Green's function has an important impact on eliminating the path effect. (2) The energy magnitude M-e of the Wenchuan earthquake is 8. 04. The correction of the focal mechanism can make the standard deviation of M, smaller and the result more stable. (3) The seismic moment of the Wenchuan earthquake obtained by inversion is 8. 97X10(20) N . m, which is converted into a moment magnitude M-w of 7. 9, and M-e is 0. 14 higher than M-w, indicating that the seismic radiated energy of the Wenchuan earthquake is high. (4) The energy-moment ratio of the Wenchuan earthquake is 3. 17 X 10(5), which is about 2. 6 times the average energy-moment ratio of global shallow earthquakes and about 4 times the average of the global thrust earthquakes. It shows that the release efficiency of seismic radiated energy of the Wenchuan earthquake is high. Taking the logarithm of the energy-moment ratio, the slowness coefficient can be obtained as -4. 50. The slowness coefficient is more direct perceived to show the release efficiency of the seismic radiated energy, which is more suitable for promotion among the general public. (5) New seismic parameters, such as seismic radiated energy, energy magnitude, energy-moment ratio, slowness coefficient, and equivalent magnitude difference, can quantitatively represent the dynamic characteristics of the source, and are of great significance for the rapid assessment of seismic disasters.