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| | Abstract | | The Kego fault runs through the central Fukuoka city. If we have a big earthquake caused by Kego fault, we will suffer the large damage. We have carried out the densed gravity survey at 1484 points, using Scintrex CG-3 and CG-3M gravimeters.We detected some high gradient zones of Bouguer anomaly, which are caused by faults. A high gradient zone of Bouguer anomaly was detected along the Kego fault. And, the triangular low Bouguer anomaly zone is the same zone called Tenjin basin decided by the borehole geological data. We can define that such area have less stability in basement compared with surrounding area. We carried out 2D structural analysis using gravity survey data, then it is estimated the depth of tertiary deposit is presumed to be 150-280m. We suggest that Bouguer anomaly reflects the depth of basement rocks and we can utilize the Bouguer anomaly map for making an earthquake hazard map. |
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