1996 Fiscal Year Final Research Report Summary
Measurement of AE and electric potential changes of rock samples under cyclic loading
| Project/Area Number |
07640559
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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 |
固体地球物理学
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| Research Institution | College of Industrial Technology, Nihon University |
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Principal Investigator |
MOGI Kiyoo Nihon University, College of Industrial Technology, Professor, 生産工学部, 教授 (40012893)
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| Co-Investigator(Kenkyū-buntansha) |
OGURA Koichi Nihon University, College of Industrial Technology, Professor, 生産工学部, 教授 (60059681)
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| Project Period (FY) |
1995 – 1996
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| Keywords | cyclic loading / electric potential / AE / rock fracture / tension crack / earthquake precursor |
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| Research Abstract |
There are a number of reports that changes in geoelectric potential and anomalous radiation of geoelectromagnetic waves have been observed befor major earthquakes. If these phenomena are earthquake precursors, they may be useful for earthquake prediction. Therefore, clarification of the mechanism of changes in geoelectric potential is an important problem.
In previous studies, measurements of electric potential related to rock fracture have been carried out under the monotonously increasing compressive stress in laboratory. In the present experiment, AE and electric potential from a rock sample were measured under the cyclic loading. A rectangular granite sample ruptured after 2300 cyclic loading of bending type.
The experimental results are summarized as follows : (1) Electric potential signals (EP) occur simultaneously with AE events. (2) EP and AE rapidly increase just before the main rupture. (3) EP signals with large amplitude occur together with large AE events. (4) AE and EP mainly occur in the stage in which the stress is increasing and reaches at the highest level in each cycle.
According to our previous study, new cracks appear and extend in the stage in which the stress is increasing and reaches at the highest level. Therefore, the present result shows that EP occurs by the generation of a new crack and its extension.
The result that EP rapidly increase just before the main rupture suggests that the geoelectric potential may be useful as a precursory phenomena.
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