THE SOURCE INVERSION WITH ELEMENT SOURCE WAVEFORMS INCLUDING RUPTURE DIRECTIVITY ON EACH SUBFAULT BY CONVOLUTION TECHNIQUE

In order to get knowledge about the physics of earthquake rupturing more precisely and to obtain reliable source process for near-source ground motion simulation, we introduced a convolution method (Ben-Menahem, 1961) which incorporate the effect of moving dislocation over a rectangular area to a point source synthetic into computation of element source waves for the waveform inversion. Therefore, the rupture directivity effect on the entire fault area is fully considered in the waveform inversion. The rupture process inverted using this technique has a smooth slip distribution even inside the subfaults. Obtained moment release history on each subfault directly reflects a slip time function on the subfault because the rupture propagation effect inside each subfault is separated. Validity of this technique is based on the following approximation; the Green’s functions from two point sources are approximately the same after phase correction when the distances between two point sources is much smaller than the distance between the sources and an observation station. The condition to validate the usage of this technique has been found through numerical tests in our previous work. We applied this technique in the waveform inversion for the source process of the 1995 Hyogo-ken Nanbu earthquake. The global characteristics of moment release distributions are similar between two inversion results; one inverted with point source element waveforms and the other with element source waves considering the finite moving dislocation effects inside each subfault. But details like places of peak moment releases differ between these inversion results. Positive correlation between final slip and peak slip velocity are observed.