小浪底水库区震源机制解特征
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摘要
利用小浪底水库台网8个台站的地震波形数据,采用垂直向P波、S波最大振幅比和初动方法测定2009年1月—2012年12月水库区域45次小地震的震源机制。结果表明:该区域45次震源机制中正断层13次、逆断层15次,走滑断层17次;主压应力轴(P轴)总体为NEE方向(220°～230°),与华北地区近水平构造应力场不完全一致,显示了小浪底水库区域受华北构造应力场的控制作用较弱,应该与水库区域地下介质构造复杂和水库蓄水有关。
Based on the first motions of P,SV waves and their amplitude ratio,we calculated focal mechanism solutions of 45times small earthquakes occurred in the Xiaolangdi reservoir area from January 2009to December 2012.The results show that:45focal mechanisms contain 13normal fault types,15thrust fault types and 17strike slip types;the direction of the maximum compressive stress axis(P-axis)is NEESWW(220°～230°),which is not completely consistent with the nearly horizontal tectonic stress field of North China,and indicate the tectonic stress field of North China has less controlling action in the Xiaolangdi Reservoir area.This phenomenon would relate to the complex structure of subsurface media and reservoir water storage.
Based on the first motions of P,SV waves and their amplitude ratio,we calculated focal mechanism solutions of 45times small earthquakes occurred in the Xiaolangdi reservoir area from January 2009to December 2012.The results show that:45focal mechanisms contain 13normal fault types,15thrust fault types and 17strike slip types;the direction of the maximum compressive stress axis(P-axis)is NEESWW(220°～230°),which is not completely consistent with the nearly horizontal tectonic stress field of North China,and indicate the tectonic stress field of North China has less controlling action in the Xiaolangdi Reservoir area.This phenomenon would relate to the complex structure of subsurface media and reservoir water storage.
引文
[1]Kisslinger C,Bowman J R,Koch K.Procedures for computing focal mechanisms from local(SV/P)z data[J].Bulletin of the Seismologi-cal Society of America,1981,87(6):1719-1730.
[2]Snoke J A,Munsey J W,Teague A G,et al.A program for focal mechanism determination by combined use of polarity and SV-P ampli-tude ratio data[J].Earthquake Notes,1984,55(3):15-22.
[3]Snoke J A.Earthquake mechanism[C].James D E.Encyclopedia of Geophysics.New York:Van Nostrand Reinhold Company,1989:239-245.
[4]刘杰,郑斯华,康英,等.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震.2004,24(1):19-26.
[5]倪红玉,刘泽民,沈小七,等.利用FOCMEC方法计算震源机制解的影响因素分析—以九江-瑞昌MS5.7地震为例[J].华北地震科学,2011,(3):1-7.
[6]胡新亮,刁桂苓,马瑾,等.利用数字地震记录的P、S振幅比资料测定小震震源机制解的可靠性分析[J].地震地质,2004,26(2):347-354.
[7]刁桂苓,徐锡伟,陈于高,等.汶川MW7.9和集集MW7.6地震前应力场转换现象及其可能的前兆意义.地球物理学报,2011,54(1):128-136.
[8]李饮祖,靳雅敏,于新昌.华北地区的震源机村与地壳应力场[J].地震学报,1982,4(1):55-61.
[2]Snoke J A,Munsey J W,Teague A G,et al.A program for focal mechanism determination by combined use of polarity and SV-P ampli-tude ratio data[J].Earthquake Notes,1984,55(3):15-22.
[3]Snoke J A.Earthquake mechanism[C].James D E.Encyclopedia of Geophysics.New York:Van Nostrand Reinhold Company,1989:239-245.
[4]刘杰,郑斯华,康英,等.利用P波和S波的初动和振幅比计算中小地震的震源机制解[J].地震.2004,24(1):19-26.
[5]倪红玉,刘泽民,沈小七,等.利用FOCMEC方法计算震源机制解的影响因素分析—以九江-瑞昌MS5.7地震为例[J].华北地震科学,2011,(3):1-7.
[6]胡新亮,刁桂苓,马瑾,等.利用数字地震记录的P、S振幅比资料测定小震震源机制解的可靠性分析[J].地震地质,2004,26(2):347-354.
[7]刁桂苓,徐锡伟,陈于高,等.汶川MW7.9和集集MW7.6地震前应力场转换现象及其可能的前兆意义.地球物理学报,2011,54(1):128-136.
[8]李饮祖,靳雅敏,于新昌.华北地区的震源机村与地壳应力场[J].地震学报,1982,4(1):55-61.
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