抄録
The Hoyo straits lies between Shikoku island and Kyushu island.
We are now planning to construct the Shinkansen tunnel under this straits (the undersea length is about 14km). The geological investigation for this project was started in 1975. The main points of the investigation are as follows:
a. Land approach portion: Geological survey seismic prospecting, boring, magnetic prospecting
b. Undersea portion: Submarine observation, dredging, sonic-prospecting, undersea boring
At present, the geological investigation is still continuing, but so far have revealed that the area is underlain with green schist of palaeozoic formations and diluvial unconsolidated seabed deposits.
To continue these, next points should be studied in further detail
a. The placement and characteristics of faults.
b. The distribution and thickness of unconsolidated seabed deposits.
