地壳持续加速变形与地震关系的研究
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摘要
借助岩石破裂实验和理论研究中得到的变形失稳准则 ,探讨了岩体持续加速变形中地震短期前兆信息的定量检测方法 ,讨论了极值变形与地震三要素之间的关系。结合川滇地区倾斜、应变现有观测能力 ,得到了倾斜、应变失稳变化的速度阈值 K- Slope分别为 4 .5 m s/d和 5 0× 10 - 8d。对 1990年至 2 0 0 1年 5月间发生在川滇及临近地区的 9次 5 .8级以上地震 (未包括强震的短期前震和余震 )的统计结果表明 :持续时间在 2 0天以上、速度超过 4 .5 m s/d的加速倾斜之后 ,在 15 0天之内有 8次地震对应 (无虚报 ) ,1次漏报 ;而持续加速应变变化之后 ,有 5次地震对应 ,4次漏报。该结果一方面反映了连续变形对地震的监测能力 ,另一方面也表明持续加速变形中存在速度临界值 ,该临界值体现了自然环境的年变化与孕震条件下变形速度的差异性
On the basis of criterion of deformation instability from rock experiment, this paper has explored the detecting method for short term seismic precursor from CAD, and has discussed the statistic relationships between characteristics of CAD and earthquakes. According to the tilt and strain monitoring ability at stations in Yunnan Sichuan, we obtained the threshold values of tilt and strain for identifying instability, that is 4.5ms/d and 50×10\+\{-8\}/a. respectively.Analyzing the CAD behaviors before 9 earthquakes (short term foreshocks and aftershocks not considered) with magnitude not less than 5.8 occurred from 1990 to May 2001 in Yunnan Sichuan, we have found that 8 earthquakes occurred within 150 days after the CAD with duration more than 20 days and tilt velocity greater than 4.5 ms/d, and without canard, but one earthquake lost. However, because the number of strain observation sites is not enough, only 5 earthquakes occurred after CAD, and before 4 earthquakes CAD have not been observed. So above result implies that the relation between CAD and earthquakes is dependent on the deformation monitoring ability, and there is a velocity threshold value for seismic and aseismic CAD in the area with higher monitoring ability. The velocity threshold value for seismic and aseismic CAD marked K-Slope, which is similar to the parameter K in the instability model of rock rupture experiment. This paper is available for identifying the short term seismic precursor from data with annual components.
On the basis of criterion of deformation instability from rock experiment, this paper has explored the detecting method for short term seismic precursor from CAD, and has discussed the statistic relationships between characteristics of CAD and earthquakes. According to the tilt and strain monitoring ability at stations in Yunnan Sichuan, we obtained the threshold values of tilt and strain for identifying instability, that is 4.5ms/d and 50×10\+\{-8\}/a. respectively.Analyzing the CAD behaviors before 9 earthquakes (short term foreshocks and aftershocks not considered) with magnitude not less than 5.8 occurred from 1990 to May 2001 in Yunnan Sichuan, we have found that 8 earthquakes occurred within 150 days after the CAD with duration more than 20 days and tilt velocity greater than 4.5 ms/d, and without canard, but one earthquake lost. However, because the number of strain observation sites is not enough, only 5 earthquakes occurred after CAD, and before 4 earthquakes CAD have not been observed. So above result implies that the relation between CAD and earthquakes is dependent on the deformation monitoring ability, and there is a velocity threshold value for seismic and aseismic CAD in the area with higher monitoring ability. The velocity threshold value for seismic and aseismic CAD marked K-Slope, which is similar to the parameter K in the instability model of rock rupture experiment. This paper is available for identifying the short term seismic precursor from data with annual components.
引文
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2 NiuAnfu,L iXudong,WuJing.The m ethod ofAF syn-thetic detection of crust deform ation anom aly and its ap-plication in earthquake prediction[J].ActaSeismologicaSinica,1998,11(3),467-472.(inChinese)
3 NiuAnfu,et al.The characteristics of deformationanom aly distribution[J].Earthquake,1999,19(2),149-154.(inChinese)
4 ChenRong.The m echanics capability of crust rock[M].Beijing:SeismicPress,1998.(inChinese)
5 ZhangGuomin,FuZhengxiang.Introduction of earth-quake prediction[M].SciencePress,2001,368-372.(inChinese)
6 MeiShirong,FengDeyi,ZhangGuom in.Introduction ofearthquake prediction inChina[M].Beijing:Seism icPress,1993.(inChinese)
7 ZhouSuoyu,ChenZilin.On the m echanism of short-term precursor and deformation remarks[J].Crust de-formation and earthquake,1993,13(Sup2),16-22.(inChinese
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