| Calculation of the parameters of georesistivi－ty anisotropy and case history of earthquake precursors |
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| 引用本文： | 钱复业,赵玉林,黄燕妮.Calculation of the parameters of georesistivi－ty anisotropy and case history of earthquake precursors[J].地震学报(英文版),1996,9(4):617-627. |
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| 作者姓名： | 钱复业 赵玉林 黄燕妮 |
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| 作者单位： | FU YEQIAN 1)，YU LINZHAO 1) and YAN NIHUANG 2) 1) Institute of Geophysics，State Seismological Bureau，Beijing 100081，China 2) State Committee for Family Planning，Beijing 100088，China |
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| 摘 要： | Ｃａｌｃｕｌａｔｉｏｎｏｆｔｈｅｐａｒａｍｅｔｅｒｓｏｆｇｅｏｒｅｓｉｓｔｉｖｉ┐ｔｙａｎｉｓｏｔｒｏｐｙａｎｄｃａｓｅｈｉｓｔｏｒｙｏｆｅａｒｔｈｑｕａｋｅｐｒｅｃｕｒｓｏｒｓＦＵ－ＹＥＱＩＡＮ１）（钱复业），ＹＵ－ＬＩＮＺＨＡＯ１）（赵玉林）ａ...
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| 收稿时间： | 23 January 1995 |
| 修稿时间： | 30 April 1996 |
Calculation of the parameters of georesistivity anisotropy and case history of earthquake precursors |
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| FU YEQIAN ,YU LINZHAO and YAN NIHUANG Institute of Geophysics,State Seismological Bureau,Beijing ,China State Committee for Family Planning,Beijing ,China.Calculation of the parameters of georesistivity anisotropy and case history of earthquake precursors[J].Acta Seismologica Sinica(English Edition),1996,9(4):617-627. |
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| Authors: | FU YEQIAN YU LINZHAO and YAN NIHUANG Institute of Geophysics State Seismological Bureau Beijing China State Committee for Family Planning Beijing China |
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| Institution: | (1) Institute of Geophysics, State Seismological Bureau, 100081 Beijing, China;(2) State Committee for Family Planning, 100088 Beijing, China |
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| Abstract: | This paper has discussed the effective resistivity ellipse and the paradoxical phenomenon of anisotropy. Two cases have been
discussed, namely: there are three measuring lines at arbitrary angles with one another and there are two mutually perpendicular
measuring lines and an additional measurement of the transversal effective resistivity. For these cases, the paper has given
the methods for quantitatively calculating the parameters of georesistivity anisotropy. The formulae given include those for
calculating the azimuth (of the principal axis of minimum resistivityρ
1, the average resistivity (ρ
1
ρ
3)1/2, (ρ
2
ρ
3)1/2, and the anisotropy coefficientλ = (ρ
2/ρ
1)1/2. As a case history, the data observed by the Datong geoelectricity station have been processed with reference to the results
ofin situ resistivity measurement in media subjected to shear. The results of analysis have led to the following understandings. Before
and after the DatongM
S6. 1 earthquake on October 19, 1989, the abnormal rise of NE-trending georesistivity and abnormal fall of NW-trending georesistivity
observed at the Datong and Yangyuan stations were caused by the pure shear acting on the medium. The major principal compression
was in NE-direction, which made an acute angle with the strike of the seismic fault plane, and thus there was a greater shear
stress but very small normal stress so that the fault was likely to slide but the earthquake was only of moderate magnitude.
The states of stress in medium were the same before and after earthquake and therefore the georesistivity precursor was of
the same sign as that of co-seismic variations.
Contribution No. 96A0082. Institute of Geophysics, SSB, China.
This project is supported by the Chinese Joint Seismological Science Foundation. |
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| Keywords: | effective resistivity ellipse paradox of anisotropy Datong M S6 1 earthquake geoelectric precursor pure shear |
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