Crustal Structure of the Japanese Islands Revealed by Explosion Seismic Observations

Abstract

The Research Group for Explosion Seismology of Japan, founded in 1950, have continuously conducted many explosion seismic observations in various regions of the Japanese Islands. Active investigations of the Group have provided important data about the crustal structure beneath the Japanese Islands which is quite useful as the most basic information for various researches of geosciences. After ages of the cradle in 1950's, the Group experienced large scale investigations under the International Upper Mantle Project and the International Geodynamics Project in 1960's and 1970's, and general features of crustal structure beneath the Japanese Islands became clear through the investigations in this period. Since 1979, the Group has conducted the investigations under the Japanese Earthquake Prediction Project in order to accumulate basic data for earthquake prediction researches. The series of these investigations have been conducted through highly dense observations, and the obtained data have revealed quite complex structure of the crust beneath the Japanese Islands. Application of some of data processing techniques in reflection survey to those data also revealed clear images of the subducted Philippine Sea plate beneath the Japanese Islands.