1998 Fiscal Year Final Research Report Summary
Study on Concealed Active Fault in the Urban Area of Kobe
| Project/Area Number |
09640543
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Kobe University |
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Principal Investigator |
MIYATA Takao Kobe University Faculty of Science Professor, 理学部, 教授 (00107989)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Hyogoken-Nanbu Earthquake / concealed active fault / Goshukebashi Fault / Ground-penetrating radar / flexure / strongly-damaged lines of lifelines / Kobe urban area |
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| Research Abstract |
We investigated , the relationship between the co-seismic ground damages during the 1995 Hyogoken-Nanbu Earthquake (M_<JMA> 7.2) and the concealed active faults in the urban area of Kobe. The ground damages were estimated from 1307 inclined utility poles and 1,277 dislocated house inlets. We used the ground-penetrating radar (GPR) method with the 200 MHz and 100 MHz antennas for the detailed examination of the concealed active faults, which were found by seismic reflection surveys (Hyogo Prefecture Government, Committee on Earthquake Observation and Research in Kansai Area, etc.). The following results were obtained in the urban area of Kobe : (1) The strong ground damages have the characteristic pattern, distributing as spots and lines. The linear distribution is consistent with w southwestward extension of the well-known Goshukebashi fault in the Rokko Mountains. (2) the two zones of deformation in the Late Pleistocene to Holocene strata such as discontinuity and flexure were found in a subsurface zone of 10 m wide : One is located just over the concealed fault (Oji fault), and the other is at the Mikage flexure beneath the Ishiyagawa River Park, Kobe City. They appeared respectively to the southwestward extension from the Gosukebashi fault and the Mikage flexure. (3) The two deformation zones on the GPR profiles, are in harmony with the strongly-damaged lines of lifelines (utility poles, house inlets etc.) during the earthquake.
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