岫岩地震序列的平均波速比前兆异常
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摘要
主要利用辽宁数字地震台网的数据并补充部分模拟台网的资料,得到岫岩地震序列1999年11月~2000年5月2级以上地震的P、S波到时,共计包含302个事件接近12000个到时数据,纵、横波到时差约4~32s,选取同时被5个或5个以上台站所记录到的地震,由最小二乘法计算平均波速比。为了保证结果的可靠性,计算每次地震的平均波速比所使用台站的数目在20个左右;全部拟合结果的相关系数超过0.99,标准误差s小于1,s的均值为0.48。全部地震波速比的平均值是1.71,稍低于线弹性体的比值1.73。分析认为:事件通过相对定位法修订震源位置,绝大多数地震的震源深度在10~12km。那么地震波射线经过的路径是从此深度到地表台站,平均波速比所反映的是地壳上层的状态。波速比的滑动平均值在1999年11月29日的5.4级主震和2000年1月12日的5.0级强余震前出现连续低值的异常现象。讨论认为5级震前的异常变化结果可信。
The arrival times of P and S wave for the over M2 earthquakes in the series of Xiuyan earthquake from Nov.of 1999 to May of 2000 are obtained with the data recorded by Liaoning Digital Seismic Network and some other analogue networks.The results contain 302 events and nearly 12000 arrival times,in which the arrival time difference is about 4-32s.The mean VP/VS ratio is calculated with least squares method when 5 or over 5 records are selected.In order to ensure the reliability of the results,the number of stations that used in calculation for each earthquake is at about 20.The correlation coefficient of the fitting results is over 0.99,standard error s is less than 1,and mean s is 0.48.The mean value of the total VP/VS ratios is 1.71,which is a little lower than the ratio 1.73 of linear elastic body.The depth of hypocenter for most earthquakes located with relative locating method is at about 10-12km.The path of seismic wave ray was from this depth to the surface station,and the state that mean VP/VS ratio reflected was that of the upper crust.The moving average value of VP/VS ratio showed continuously low value anomaly both before the M5.4 main shock occurred on Nov.29,1999 and the M5.0 strong aftershock occurred on Jan.10,2000.We believe these anomalies are credible.
The arrival times of P and S wave for the over M2 earthquakes in the series of Xiuyan earthquake from Nov.of 1999 to May of 2000 are obtained with the data recorded by Liaoning Digital Seismic Network and some other analogue networks.The results contain 302 events and nearly 12000 arrival times,in which the arrival time difference is about 4-32s.The mean VP/VS ratio is calculated with least squares method when 5 or over 5 records are selected.In order to ensure the reliability of the results,the number of stations that used in calculation for each earthquake is at about 20.The correlation coefficient of the fitting results is over 0.99,standard error s is less than 1,and mean s is 0.48.The mean value of the total VP/VS ratios is 1.71,which is a little lower than the ratio 1.73 of linear elastic body.The depth of hypocenter for most earthquakes located with relative locating method is at about 10-12km.The path of seismic wave ray was from this depth to the surface station,and the state that mean VP/VS ratio reflected was that of the upper crust.The moving average value of VP/VS ratio showed continuously low value anomaly both before the M5.4 main shock occurred on Nov.29,1999 and the M5.0 strong aftershock occurred on Jan.10,2000.We believe these anomalies are credible.
引文
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[13]张成科,张先康,赵金仁,等.渤海湾及其邻区壳幔速度结构研究与综述[J].地震学报,2002,24(4):428-435.
[14]祝治平,张先康,盖玉杰,等.邢台震源区及其邻近地区地壳上地幔速度结构研究[J].地震学报,1992,27(3):328-334.
[15]Jinli Huang,Dapeng Zhao,Crustal heterogeneity and seismotectonics of the region around Beijing,China[J].Tectonophysics,2004,385,159-180.
[16]于湘伟,陈运泰,王培德.京津唐地区中上地壳三维P波速度结构[J].地震学报,2003,25(1):1-14.
[17]傅征祥,程燕.北京和张家口地区地壳平均波速比的联合测定[J].地震,1988,(4):28-34.
[18]嘉世旭,刘昌铨.邢台震源区波速比异常与地震的关系[J].地震学报,1996,39(supp):205-215.
[19]栗生平,傅征祥.华北地区地震带分段波速比平均值的测定,见:国家地震局科技发展司,中国大陆2005年前强震危险性预测研究[M].北京:地震出版社,1997,96-99.
[20]黎晓明,张晓东.应用多台法测定华北地区地壳的平均波速比[J].地震,2004,24(1):163-169.
[21]张学民,刁桂苓,束沛镒,等.华北地区地下介质波速比值(Vp/Vs)研究[J].地震地质,2004,26(2),305-317.
[22]张学民,刁桂苓,束沛镒.鄂尔多斯块体及其东南缘剪切波速度结构与波速比研究[J].中国地震,2004,20(1):53-67.
[23]高常波,钟以章.1999年辽宁海城-岫岩6.6级地震地质构造背景和发震构造[J].地震地质,2000,22(4):405-412.
[24]吕培苓,杨智娴,王晓青,丁香,窦爱霞.1999年岫岩地震序列研究[J].地震,2004,24(4):45-50.
[25]陈学忠,郭铁栓,朱令人.一次大陆强震前震成核的实例[J].地震学报,2001,23(2):21321-6.
[26]王伟君,刘杰.1999年岫岩地震序列尾波Qc变化过程[J].地震.2004.24(4):37-44.
[27]刘元生,刘贵和,佟凤兰.辽河盆地地下流体异常与岫岩Ms5.6地震[J].西北地震学报,2000,22(3):241-246.
[2]Semenov,A.N.Variations of the travel time of transverse and longitudinal waves before violent earthquakes[J].Izv.Acad.Sci.USSR,Phys.Solid Earth 1969,3:245-258.
[3]Aggarwal,Y.P.,Sykes,L.R.,Simpson,D.W.,and Richards,P.G.Spatial and temporal variations ofts/tp and in P wave residuals atBlue Mountion Lake,New York:Application to earthquake prediction.J.Grophys.Res.1973,80:718-732.
[4]Nur,A.Dilatancy,pore fluids,and premonitory variations in tp/ts travel times[J].Bull.Seismol.Soc.Am.1972,62:1217-1222.
[5]McMvilly,T.V.and Johnson,L.R.Stability of p and s velocities from central California quarry blasts[J].Bull.Seismol.Soc.Am.1974,64:343-353.
[6]Mogi,K.Earthquake Prediction[M].Tokyo:Academic press.1985.
[7]冯德益.地震波速异常[M].北京:地震出版社,1981,21-23,3-637.
[8]梅世蓉,冯德益,张国民,等.中国地震预报概论[M].北京:地震出版社,1993,78-80.
[9]陆远忠,陈章立.地震预报的地震学方法[M].北京:地震出版社,1985,175-196.
[10]蔡静观,张喜玲,李永莉,等.云南地区近期强震孕育过程中波速比突变的时空演化特征[J].地震学报,1997,19(5):535-541.
[11]顾瑾平,虞雪君,盛国英.滇西地区波速比的试验研究[J].地震研究,1987,10(5):561-574.
[12]张天中,刘庆芳,武巴特尔.线性度量误差模型和波速比模拟计算,陈运泰等主编,中国大陆地震学与地球内部物理学研究进展[M].北京:地震出版社,2004,723-726.
[13]张成科,张先康,赵金仁,等.渤海湾及其邻区壳幔速度结构研究与综述[J].地震学报,2002,24(4):428-435.
[14]祝治平,张先康,盖玉杰,等.邢台震源区及其邻近地区地壳上地幔速度结构研究[J].地震学报,1992,27(3):328-334.
[15]Jinli Huang,Dapeng Zhao,Crustal heterogeneity and seismotectonics of the region around Beijing,China[J].Tectonophysics,2004,385,159-180.
[16]于湘伟,陈运泰,王培德.京津唐地区中上地壳三维P波速度结构[J].地震学报,2003,25(1):1-14.
[17]傅征祥,程燕.北京和张家口地区地壳平均波速比的联合测定[J].地震,1988,(4):28-34.
[18]嘉世旭,刘昌铨.邢台震源区波速比异常与地震的关系[J].地震学报,1996,39(supp):205-215.
[19]栗生平,傅征祥.华北地区地震带分段波速比平均值的测定,见:国家地震局科技发展司,中国大陆2005年前强震危险性预测研究[M].北京:地震出版社,1997,96-99.
[20]黎晓明,张晓东.应用多台法测定华北地区地壳的平均波速比[J].地震,2004,24(1):163-169.
[21]张学民,刁桂苓,束沛镒,等.华北地区地下介质波速比值(Vp/Vs)研究[J].地震地质,2004,26(2),305-317.
[22]张学民,刁桂苓,束沛镒.鄂尔多斯块体及其东南缘剪切波速度结构与波速比研究[J].中国地震,2004,20(1):53-67.
[23]高常波,钟以章.1999年辽宁海城-岫岩6.6级地震地质构造背景和发震构造[J].地震地质,2000,22(4):405-412.
[24]吕培苓,杨智娴,王晓青,丁香,窦爱霞.1999年岫岩地震序列研究[J].地震,2004,24(4):45-50.
[25]陈学忠,郭铁栓,朱令人.一次大陆强震前震成核的实例[J].地震学报,2001,23(2):21321-6.
[26]王伟君,刘杰.1999年岫岩地震序列尾波Qc变化过程[J].地震.2004.24(4):37-44.
[27]刘元生,刘贵和,佟凤兰.辽河盆地地下流体异常与岫岩Ms5.6地震[J].西北地震学报,2000,22(3):241-246.
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