1995年永登5.8级地震多种前兆异常特征
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摘要
研究了１９９５年７月２２日甘肃永登５．８级地震地电、水化学、水动态、地应力、地形变等５种前兆的异常特征，得到如下结论：①该次地震中短期（１年尺度）和短临异常空间分布符合“异常震源地点发震机制主要活断层”之间的特定关系，近２～３年的中期异常集中分布在西秦岭北缘北西向断裂带和海原通渭武都南北向断裂带上；②震前约１年时间尺度震源区发育起来了北北西南南东向挤压变化突出的附加应力场，并引起断层错动；③源兆集中分布在本次地震震源周围，场兆集中分布在上述两条活动断裂带上．源兆占异常的大多数，场兆占少数．在时间上场兆出现在先，源兆在后．
Anomaly characteristics of earth resistivity,hydrochemistry,underground water behaviors,ground stress and deformation during the Yongdeng M S5.8 earthquake in Gansu Province on Jul. 22, 1995 were studied, and so the following conclusions were obtained: ① The spatial distribution of medium short (one year time scale) and short imminent anomalies accords with the special relation of anomaly focal site causitive mechanism active master fault put forth by authors, and the medium period anomaly which lasted about 2 3 years is concentratedly distributed along the NW fault zone on north margin of west Qinling mountain and Haiyuan Tongwei Wudu fault zone. ② The additional compression stress field in the NNW SSE direction come into being during one year before the earthquake, which caused the displacement of the focal fault. ③ The focal precursors are concentratedly distributed around the focal area, while the field precursors occur along the two active master faults mentioned above. Most of anomalies belong to the focal precursors, while a few anomalies are the field precursors. As far as duration time of anomalies,the field precursors appeared more precedently than the focal precursors.
Anomaly characteristics of earth resistivity,hydrochemistry,underground water behaviors,ground stress and deformation during the Yongdeng M S5.8 earthquake in Gansu Province on Jul. 22, 1995 were studied, and so the following conclusions were obtained: ① The spatial distribution of medium short (one year time scale) and short imminent anomalies accords with the special relation of anomaly focal site causitive mechanism active master fault put forth by authors, and the medium period anomaly which lasted about 2 3 years is concentratedly distributed along the NW fault zone on north margin of west Qinling mountain and Haiyuan Tongwei Wudu fault zone. ② The additional compression stress field in the NNW SSE direction come into being during one year before the earthquake, which caused the displacement of the focal fault. ③ The focal precursors are concentratedly distributed around the focal area, while the field precursors occur along the two active master faults mentioned above. Most of anomalies belong to the focal precursors, while a few anomalies are the field precursors. As far as duration time of anomalies,the field precursors appeared more precedently than the focal precursors.
引文
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