Verification of the Debate on the Takamatsu Crater

Abstract

 The Takamatsu crater is a buried depression structure found by a low gravity anomaly in the southern part of the Takamatsu Plain, northeast Shikoku, Japan (Kono et al, 1991). The Takamatsu crater had been proposed as the first impact crater in Japan and a huge underground reservoir. The debate on the origin and estimation of groundwater of the Takamatsu crater had been continued since 1994, and has ended in 2004. The author has estimated the origin and groundwater of the Takamatsu crater by the CSAMT method and borehole logs. They suggest that the Takamatsu crater is cauldron origin. Limited pumping tests in the cauldron have shown that the pumping capacity was 100-150t/day. Therefore the Takamatsu crater cannot be a huge underground water reservoir. The author has refuted almost every time against one-sided opinions reported by mass media and has explained from the viewpoint of engineering geology. This might prevent troubles and lost the credit with the citizen.