RESEARCH-AND-DEVELOPMENT ON THE MULTICHANNEL SEISMIC-REFLECTION METHOD AND ITS APPLICATIONS TO VARIOUS GEOLOGICAL SITUATIONS IN JAPAN

Recent trends in reflection seismology, mainly on land, are reviewed h ere. Almost all material discussed in this review comes from those pub lished in journals and presented at meetings of some societies related to seismology within the past ten years or so. Notable features of th e past ten years or so are: (1) The development and application of the shallow seismic reflection method with high resolution, which is wide ly being used for detailed research on active faults and for surveys o f the ground properties. (2) Applications of the seismic reflection me thod to various geological situations, such as faulted areas, tectonic areas, volcanic areas, the deep crust, and so on. (3) Trials for cons truction of smaller and easier exploration systems based on personal c omputers, which are now widely being used mainly in universities and a re producing many reflection sections. Although until about ten years ago only a small number of specialists worked on the reflection method , many people who are interested in the reflection method have begun t o work in this area. At present the seismic reflection method covers t he depth range from several meters to a few tens of kilometers. The hi ghest resolution is about 10 m in P-wave surveys and a few meters in S -wave surveys.