Abstract
The article presents a 3D analysis method by interpolating borehole data to improve the precision of the surface model of the base of the latest Pleistocene to Holocene incised-valley fill, called the Chuseki-so in Japan. The study area is located in the northeastern part of the metropolis, where the northern Tokyo and the southern Nakagawa lowlands meet and are surrounded by adjacent uplands. A borehole database for this area was used for analysis.
The procedure to construct the surface model involves the following steps : (1) generate primary point data of (a) the basal horizon of the Chuseki-so using borehole data, (b) a 3D boundary line between the alluvial lowland and the adjacent Pleistocene upland areas, and (c) the adjacent upland area using a digital elevation model at a 5-m grid resolution; (2) add secondary point data to adjust the geomorphic form of both the valley branches and boundary lines between terraces and cliffs buried by the Chuseki-so; (3) generate point data of each buried river terrace and abrasion platform, and finally; (4) construct the surface model by spatially interpolating the point data generated in steps 1–3.
It is necessary to consider the geologic and geomorphic formation process and evolution of this area so as to improve the form of the surface model of the base of the Chuseki-so and to better understand the geomorphic features of the incised-valley.
