Abstract
Although geoinformation pertaining to urban areas is very important, paper-based geological maps do not adequately describe the subsurface geological conditions of urbanized plains. A three-dimensional geological map, available via the Internet, is expected to provide intelligible, highly reliable, and easily utilizable geoinformation for urban areas. In this case, a three-dimensional geological model needs to be constructed on the basis of reliable borehole data using an advanced modeling tool. We are now developing a prototype of a three-dimensional geological map of the northern part of Chiba Prefecture as a new form of urban geoinformation which contributes to estimating the risk of geological disasters.