抄録
Seismic wave records at the surface of sedimentary plain are mainly composed of main phase and surface waves. The informations of input wave record in base rock and S wave velocity distribution to base rock are enough to consider the main phase. And moreover the informations about underground structure to bed rock of all sections of plain are necessary to discuss surface wave which travels from surrounding rock range to observation point. For this items of the Osaka plain, there were some crumbs of informations. In 1988, we tried two explosions at a manmade “Hokko” island in Osaka bay. This paper shows the results: five ground structures and a countour map of depth to base rock of the Osaka plain.
