温州珊溪水库地震S波分裂研究
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摘要
通过对温州珊溪水库地震序列开展了近一年的近场源剪切波分裂参数研究,在进行精确定位并确保所用资料满足剪切波窗要求的基础上,采用互相关系数法,借助遗传算法与人工判读相结合,测量了地震序列的快剪切波偏振方向和快慢剪切波的时间延迟.结果表明,地震序列的S波分裂现象明显,台站记录到的地震快剪切波平均偏振方向与区域最大水平主压应力方向基本一致;温州珊溪水库地区快剪切波平均偏振方向在近N-S向;S波分裂快剪切波偏振方向所表现出的离散和空间差异性,认为可能是由于局部构造影响;目前库区应力场稳定,应力调整已经结束,未来发生强余震的可能性较小.
More than 1000 earthquakes induced by the Shanxi reservoir in Wenzhou,Zhejiang province of China,were recorded by both Zhejiang regional digital seismic network and Shanxi reservoir local digital network during the period from Feb.4 to Oct.31,2006.Using wave form data of these earthquakes we studied S-wave splitting characteristics in the reservoir region.The earthquakes were relocated and the S-wave records with travel paths within S-wave window were selected out for analysis.The fast wave polarity azimuth and the slow wave time delay were determined by using the technique of cross-correlation coefficient analysis.The result indicates that S-waves coming from the reservoir earthquakes show notable splitting.The average fast wave polarization azimuth obtained at different stations generally coincides with the orientation of regional maximum principal stress therein.In Shanxi reservoir region the average polarization azimuth of fast S-wave is nearly in N--S direction.The scattering and spatial variation of the deduced fast S-wave polarity may be attributed to the effect of local structure inhomogeneity.Presently the stress field in the reservoir region has recovered to stable state,and there would be little possibility of occurrence of a next strong earthquake.
More than 1000 earthquakes induced by the Shanxi reservoir in Wenzhou,Zhejiang province of China,were recorded by both Zhejiang regional digital seismic network and Shanxi reservoir local digital network during the period from Feb.4 to Oct.31,2006.Using wave form data of these earthquakes we studied S-wave splitting characteristics in the reservoir region.The earthquakes were relocated and the S-wave records with travel paths within S-wave window were selected out for analysis.The fast wave polarity azimuth and the slow wave time delay were determined by using the technique of cross-correlation coefficient analysis.The result indicates that S-waves coming from the reservoir earthquakes show notable splitting.The average fast wave polarization azimuth obtained at different stations generally coincides with the orientation of regional maximum principal stress therein.In Shanxi reservoir region the average polarization azimuth of fast S-wave is nearly in N--S direction.The scattering and spatial variation of the deduced fast S-wave polarity may be attributed to the effect of local structure inhomogeneity.Presently the stress field in the reservoir region has recovered to stable state,and there would be little possibility of occurrence of a next strong earthquake.
引文
付虹,王绍晋,王赟赟,黄毓珍,龙晓帆.2004.1999年至2001年云南几次中强震前应力场方向动态变化及其预测意义[J].地震研究,27(21):6--11.
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高原,郑斯华,孙勇.1995.唐山地区地壳裂隙各向异性[J].地震学报,17(3):283--293.
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太龄雪,高原,曹凤娟,吴晶,石玉涛,焦明若.2008.辽宁1999年MS5.9岫岩地震的剪切波分裂特征[J].地震学报,30(4):340--354.
王绍晋,龙晓帆.2000.武定6.5级地震前后环境剪应力场动态变化[J].地震研究,23(3):8--13.
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姚陈,王培德,陈运泰.1992.卢龙地区S波偏振与上地壳裂隙各向异性[J].地球物理学报,35(3):305--315.
张永久,高原,石玉涛,程万正.2008.四川地区地震台网的剪切波分裂研究[J].地震学报,30(2):123--134.
Crampin S.1978.Seismic wave propagation through a cracked solid:Polarization as possible dilatancy diagnostic[J].Geophys J R astr Soc,53(3):467--496.
Crampin S,Chastin S.2003.Areviewof shear wave splittinginthe crack-critical crust[J].Geophys J Int,155(1):221--240.
Crampin S,Volti T.2004.Asuccessfully stress forecast earthquake[J].Geophys Jlnt,157(2):578--582.
Crampin S,Gao Y.2006.Areviewof techniques for measuring seismic shear-wave splitting above small earthquakes[J].Phys Earth Planet Interi,159(1/2):1--14.
Iidaka T.2003.Shear-wave splitting analysis of later phases in southwest Japan-a lineament structure detector inside thecrust[J].Earth Planets Space,55(5):277--282.
Okada T,Matsuzawa T,Matsumoto S,Nida K,Ito A,Hasegawa A.1994.Shear wave splitting observedin the south-western part of Fukushi-ma prefecture,northeastern Japan[J].J Phys Earth,42(4):303--319.
Peng Z,Ben Zion Y.2004.Systematic analysis of crustal anisotropy along the Karadere-Duzce branch of the North Ana-tolian fault[J].Geophys Jlnt,159(1):253--274.
高原,冯德益.1995.唐山地区近震S波分裂的观测与研究[J].地震,(3):208--213.
高原,郑斯华,孙勇.1995.唐山地区地壳裂隙各向异性[J].地震学报,17(3):283--293.
高原,郑斯华,王培德.1996.海南省东方地区1992年小震群剪切波分裂研究[J].地球物理学报,39(2):221--232.
高原.2006.利用剪切波分裂研究地壳介质各向异性[J].安徽师范大学学报(自然科学版),29(3):205--211.
华卫,刘杰,陈章立,郑斯华.2006.2003年云南大姚6.2级、6.1级地震序列S波分裂研究[J].地震学报,28(4):357--371.
赖院根,刘启元,陈九辉,刘洁,李顺成,郭飙,黄志斌.2006.首都圈地区横波分裂与地壳应力场特征[J].地球物理学报,49(1):189--196.
李金龙,邹振轩,张震峰.2007.珊溪水库震群的地震定位[J].地震地磁观测与研究,28(1):14--18.
李瑞莎,崔效锋,刁桂苓,张红艳.2008.华北北部地区现今应力场时空变化特征研究[J].地震学报,30(6):21--26.
石玉涛,高原,吴晶,程万正.2006.云南地区地壳介质各向异性:快剪切波偏振特性[J].地震学报,28(6):574--585.
太龄雪,高原,曹凤娟,吴晶,石玉涛,焦明若.2008.辽宁1999年MS5.9岫岩地震的剪切波分裂特征[J].地震学报,30(4):340--354.
王绍晋,龙晓帆.2000.武定6.5级地震前后环境剪应力场动态变化[J].地震研究,23(3):8--13.
吴晶,高原,陈运泰.2008.首都圈东南部地区地壳介质各向异性[J].地震学报,30(1):1--11.
姚陈,王培德,陈运泰.1992.卢龙地区S波偏振与上地壳裂隙各向异性[J].地球物理学报,35(3):305--315.
张永久,高原,石玉涛,程万正.2008.四川地区地震台网的剪切波分裂研究[J].地震学报,30(2):123--134.
Crampin S.1978.Seismic wave propagation through a cracked solid:Polarization as possible dilatancy diagnostic[J].Geophys J R astr Soc,53(3):467--496.
Crampin S,Chastin S.2003.Areviewof shear wave splittinginthe crack-critical crust[J].Geophys J Int,155(1):221--240.
Crampin S,Volti T.2004.Asuccessfully stress forecast earthquake[J].Geophys Jlnt,157(2):578--582.
Crampin S,Gao Y.2006.Areviewof techniques for measuring seismic shear-wave splitting above small earthquakes[J].Phys Earth Planet Interi,159(1/2):1--14.
Iidaka T.2003.Shear-wave splitting analysis of later phases in southwest Japan-a lineament structure detector inside thecrust[J].Earth Planets Space,55(5):277--282.
Okada T,Matsuzawa T,Matsumoto S,Nida K,Ito A,Hasegawa A.1994.Shear wave splitting observedin the south-western part of Fukushi-ma prefecture,northeastern Japan[J].J Phys Earth,42(4):303--319.
Peng Z,Ben Zion Y.2004.Systematic analysis of crustal anisotropy along the Karadere-Duzce branch of the North Ana-tolian fault[J].Geophys Jlnt,159(1):253--274.
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