開析扇状地から知られる地殻変動東海地方を例に (第四紀テクトニクス特集)

概要

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Crustal movements deduced from the deformation of dissected fans are summarized taking those in the Tokai region, the Pacific Coast of Central Japan, as an example. Two Quaternary crustal movements are recognized in this region. One is undulations with axes of NE-SW direction, running en echelon, along the margin of the Akaishi sphenoid. The other is a diagonal upwarping with an axis of NW-SE direction, which is accompanied by the upheaval of the mountainous hinter-land. Vertical movements of the region calculated by the levelling survey during the latest 60 years have also close relation to the above-mentioned crustal movements. The rate of the vertical component of an undulation in the vicinity of Shizuoka in the south Fossa Magna amounts to 3.3mm/year, which corresponds nearly to those of upheaval indicated by the Holocene Numa coastal terrace, south Boso Peninsula, and the seismic upheaval of Oiso district, south Kanto region. The rate of the inclination in the lower courses of Tenryu and Oi rivers is estimated at 2° to 10°/106 years.The undulatory movement can be interpreted as a continuation of the Neogene crustal movement of this region with reference to the evolution of sedimentary basins, though anticlinal elevations and synclinal subsidences of the Quaternary are reciprocal to the underlying Neogene folds in the sense of the up-and down-warping.
日本第四紀学会の論文