While large-scale active fault maps are being published to present important informations for the earthquake disaster mitigation, it is necessary to estimate the accuracy of locality information shown on the maps. When the locations are digitized based on topographical maps of 1: 25,000, it is impossible to eliminate an error of about 20m which came from the accuracy of the based maps. In order to improve the accuracy of the data, we propose here a methodology for making digital locality information by use of photogrammetrical system.
As it is necessary to observe original landforms deformed prior to land modifications, aerial photographs taken in 1940s' by the U. S. Armed Forces are often used for active fault mapping. However, the photographs have been much distorted, and the mapping by the photographs are often problematic and some countermeasures should be considered carefully. By utilizing the method presented here, the error of locality information can be minified within 5-7m horizontally.
