A number of sonic boundaries which have considerable reflection coefficent were detected between the Tertiary and the basement, according to the sonic impedances which were obtained by the velocity measurement of ultra-sonic propagation on drilling cores in the Miike coal field, Kyushu.
It is unquestionable that fair response of reflections is acquired on the surface of the base-rock, near the coal seams such as the Main Seam of the Tooka Formation, the Upper Seam of Nanaura Formation, , Uppermest Seam of Kattachi Formation and so on by the result of velocity loggings and the well shootings.
Utilizing the abovementioned data, the equipment improved by the author was used in the sonic exploration. Thus, particular patterns are presented such as uncomformity, monoclinic structure, fold, lava-flow, agglomerate stock, gravel bed and fault of the Cenozoic Formation in the Ariake Sea.