抄録
High-resolution digital elevation models (DEMs) have been widely adopted as data sets that can be used, together with image processing and geographic information system technology, for geomorphological analysis. For example, shaded relief maps and bird's-eye-view images derived from DEMs are effective ways to depict topographic relief. However, not all geomorphologic features appear in DEMs because they usually consist of digital data derived predominantly from pre-existing topographic maps. Therefore, before conducting geomorphology research with DEMs, a detailed review should be conducted, to determine whether DEM resolution is sufficient to reveal the specific geomorphological features required. The aims of this report are: (1) to discuss the appearance of tectonic landforms on DEMs as they vary with DEM resolution; and (2) to present a case study on a new tool, the digital photogrammetry workstation (DPW), which can be used to construct DEMs with better detail directly from aerial photograph pairs or satellite image pairs. Well-known tectonic landforms around Chino and Fujimi along the Itoigawa-Shizuoka tectonic line are used as examples. This illustrates that 50m-resolution DEM is insufficient to indicate whether a scarp is of tectonic origin, because references such as tectonic bulges or river offsets are too subtle to appear. DEMs with 10-m resolution or better, constructed by using a DPW, might prove to be more useful in research on active faults, with the caveat that a certain amount of manual revision is inevitable when constructing DEMs.
