|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Data from the ancient shorelines along the present-day coastline of Kyushu Island, Western Japan, show that the island can be divided into several regions on the basis of modes of vertical crustal movements during the past 125,000 years. The heights of the ancient shorelines have been dectermined using paleodepth indicators such as molluscan faunas, trace fossils and sedimentary structures. The chronology of the sediments and of the tectonic events have been deduced from the well-documented history of volcanic ash events (tePhrostratigraphy) of southern Japan.
The difference between the most uplifted and subsided areas in the island during the past 125,000 years is about l90 meters. Although it was previously thought that the whole of Kyushu Island was an uplifting region throughout this time, the present work has shown that there were marked differential movemcnts. North and south west Kyushu Were steadily subsiding areas, but rapid uplift occurred locally in the southern part of the island. A subsiding axis (the Saeki-Sendai Subsiding Axis) crosses the island with a NE-SW trend, and an E-W trending structural depression (the Beppu-Shimabara Graben) is present in central Kyushu.
There is a clear correlation between the present-day coastal landform of the island and the differential tectonic movements that have occurred during the past l25,000 years.