Abstract
Attenuation of seismic ground motions is affected by the 3-D attenuation structure. The distribution of seismic intensity, of the 1993 Kushiro-Oki earthquake can not be predicted by conventional attenuation relations. We attempt to explain this phenomenon on the basis of the 3-D attenuation structure of the Japanese islands. We first obtain the 3-D attenuation structure by tomographic inversion of a large quantity of previous seismic intensity data and then simulate the seismic intensity distribution of the 1993 Kushiro-Oki earthquake using the attenuation model. Results are summarized as follows.
(1) The obtained 3-D attenuation structure shows that the Pacific plate and the Philippine Sea plate tend to show High-Q. These results are consistent with the reported results of P wave velocity tomography.
(2) The source acceleration of inland earthquakes whose depths are 0-30km is smaller than that of subduction zone earthquakes at the same depth range.
(3) It is possible to reproduce the seismic intensity distribution of the 1993 Kushiro-Oki earthquake using the obtained 3-D attenuation structure and the relationship between source acceleration and JMA magnitude.
