Abstract
The Ministry of Education, Culture, Sports, Science and Technology has employed the microtremor survey method (MSM) for conducting the project aimed at determining the subsurface structures in a sedimentary basin for strong ground motion modeling. The project planned as a national research program after the 1995 Kobe earthquake has been put in practice from 1998 to 2004 in the eight examined areas in Hokkaido and Honshu.
This paper reviewed the project report laying stress on the role of the MSM played in determining the subsurface structures, as well as on the effectiveness of the MSM to estimating the subsurface structures effectual for strong ground motion modeling. Through the review, the paper also summarized the present situation of the MSM and some subjects related to its practical application to the subsurface structure estimation.
In addition, taking a serious view of the fact that the unusually high phase velocities of waves have been estimated at a site in Tokyo for frequencies lower than 0.2-0.3 Hz as compared with those to be usually expected, the theory of the present SPAC method was reanalyzed returning to its basics on the assumption that the unexpected phase velocities estimated are due to the wave propagation in which the multimode Rayleigh-wave energy is contaminated.
