Research of the Geiyo Earthquake in 2001

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The conclusions can be summarized as follows :1) It is shown that the earthquake activities of western Japan have became active after western Tottori Earthquake occurred on the afternoon of Octobcr 6, 2000. 2) Estimates of the Q value for two profiles from the Geiyo earthquake, show that the attenuation is lower for the path that pases through the subducting Philippine Sea slab. 3) 3D gravity inversion of basement relief in the Hiroshima plain, western Japan, was performed using precise data measured in and around the plain. It is important to note that an NNE-SSW oriented trough-like depression is revealed to exist along the western edge of the plain, where damage to houses was remarkably severe. 4) On the basis of the questionnaire survey on seismic intensity in whole Chugoku and Shikoku areas mainly affected by this earthquake, the fact that higher seismic intensities than the instrumental ones were estimated in many areas by the questionnaire survey. 5) Collapse of stone retaining … More wall and slope surface collapse in cases of Kure and Kouchi districts respectively were strongly related to topographical and geological features and characteristics of observed earthquake motions. 6) The roof-tile damage of wooden houses in the residential area of hill-side looks to coincide with ground condition of cut or fill. Difference in dynamic characteristics due to micro-tremor measurement has been found between fill and cut. Moreover, the second earthquake resistance diagnosis method must be taken into account of brittle columns or shear-failed columns, in order to lead the results of earthquake resistance diagnosis of two reinforced concrete school buildings and their damage by the earthquake. 7) Although the physical damage to utility lifelines was not catastrophic as a whole, there occurred functional damage spread, which is typical of urban earthquake disaster. 8) Social responses shown by mainly people, local govemments, and private enterprises in Hiroshima prefecture after the earthquake are investigated. Less