The Kego fault runs through the central part of Fukuoka-city, extending southward to Kasuga, and Oonojo cities.
In order to estimate the fault activity during the Quaternary time and to clarify the fault's buried Quaternary topography, the author gathered drilling data in the area from Aratsu to Takamiya in Fukuoka-city, and examined the distribution of depth down to the base of the Quaternary strata lying on the Paleogene bedrocks.
The results obtained are as follows.
1. The basement on which the Quaternary strata lie changes in depth remarkably on the line connecting Aratsu and Hirao in Fukuoka-city. The basement on the southwest side of the line is shallower than 10 meters in depth, but on the northeast side, the basement is deeper than 60 meters in depth.
2. The largest difference in depth of the basement between two closely situated study points is as much as 53.0 meters at location b. Moreover, the largest gradient of the averaged slope between two study points is about 77°in the vicinity of location f.
3. It is difficult to assume the steep slope mentioned above has been formed by erosion. Thus, the slope is due to faulting along the Kego fault during the Quaternary time.
4. The Kego fault in Fukuoka-city consists of two echelon-arrange d strands a few meters apart: one is from location a to the west of location b, and the other is from location d to location f. These strands are situated 100 meters southwest to the fault line previously shown in“Fukuoka Jibanzu”.
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