A new approach for estimation of seismic moment from back projection analysis

Abstract:

Recently, array back projection analysis is used for source process analysis of many earthquakes. The back projection analysis is very useful in analyzing large and/or complex fault processes, however, the physical meaning of obtained image is still not clear. To improve this problem, we introduce a new approach as follows. First, we stack seismic waveforms observed by a seismic array in a frequency range that is lower than the corner frequency of an earthquake of which Mo is known. Second, we calculate energy of stacked waveforms. Comparing Mo and the energy of stacked waveform, we obtain a transfer coefficient between Mo and the energy. If radiation pattern at the source and geometric attenuation on the ray path are corrected, it is expected that this coefficient has a unique value for the array. Once we obtained this transfer coefficient of the array, we can estimate Mo of other earthquakes from the product of the transfer coefficient and energy of stacked waveforms. For higher frequency range, we can calculate the transfer coefficient by using scaling law of earthquakes like w-square model. We will analyze middle class earthquakes by using this approach and report the results.