云南剑川近场横波特征及其与构造的关系
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摘要
通过对1982年7月3日云南剑川Ms5．4级地震的余震震群近场记录的研究，为该地区存在横波分裂现象及上部地壳存在裂隙各向异性提供了直接的证据．剑川地区地震记录波形复杂，纵、横波视周期差异较大．横波快波偏振主要集中在NE45°和NW55°两个方向．7月20日ML4．8级强余震前后横波快波偏振取向变化显著，各台横波偏振方向震前彼此相对独立；震后整体上趋于有序．前者反映了地震发生前由于震源区应力集中在附近空间形成的应力分布的差异；后者显示出地震发生后由于震源区集中应力的释放带来的上述应力差异在一定空间范围的解除．该结果表明震源附近地区地震横波分裂特征不仅携带着地震处于相对平静期应力场的静态信息，而且也携带着地震发生前后应力场时、空动态变化的重要信息．文中还讨论了剑川地区构造对S波分裂的影响．
In thes paper, the resultS of a study about the aftershocks swarm of an earthquake of magnitude Mss.4 occurred on July 3, 1982, in Jianchuan, Yunnan province, China, was given and the existences of both shear wave splitting and extensive dilatancy anisotropy in the upper crust of Jianchuan area were recognized. The waveforms recorded in Jianchuan area are more complex. The difference of aPParent period betWeen compressional waves and shear waves is bigger and depends on the conditions of the foundation under each station. The shear wave polarization pattern is different from the unique alignment as reported in the other regions of China, and show tWo dominant directions of NE45°and NW55°. The changes of fast shear wave polarization are very obVious before and after the strong aftershock of magnitude ML 4.8 occond on July 20, 1982, which from a relative independence between stations before the shock to a relative regularization in its entirety after the shock represent that there was an intense local difference of the concentrated stress field before the shock and disaPPeared in a certain extent caused by a stress relief during the shock respectively, and also indicated that some important information concerned with the dynamic change of stress field before and after an earthquake were carried by the splitting shear waves obtained from the area near source.
In thes paper, the resultS of a study about the aftershocks swarm of an earthquake of magnitude Mss.4 occurred on July 3, 1982, in Jianchuan, Yunnan province, China, was given and the existences of both shear wave splitting and extensive dilatancy anisotropy in the upper crust of Jianchuan area were recognized. The waveforms recorded in Jianchuan area are more complex. The difference of aPParent period betWeen compressional waves and shear waves is bigger and depends on the conditions of the foundation under each station. The shear wave polarization pattern is different from the unique alignment as reported in the other regions of China, and show tWo dominant directions of NE45°and NW55°. The changes of fast shear wave polarization are very obVious before and after the strong aftershock of magnitude ML 4.8 occond on July 20, 1982, which from a relative independence between stations before the shock to a relative regularization in its entirety after the shock represent that there was an intense local difference of the concentrated stress field before the shock and disaPPeared in a certain extent caused by a stress relief during the shock respectively, and also indicated that some important information concerned with the dynamic change of stress field before and after an earthquake were carried by the splitting shear waves obtained from the area near source.
引文
[1] CRAMPIN, S, Seismic wave propagation though a cracbd solid: polarization as a possible dilatancydiagnostic, Geophys. J. R. astr. Soc., 53, 467-496,1978.
[2] Crampin, S., Geological and industrial implications of extensive-dilatancy anisotropy, Nature, 328,491-496,1987
[3] 姚陈、王培德、陈运泰,卢龙地区 S波偏振与上地壳裂隙各向异性,地球物理学报,35, 305-315, 1992。
[4] Yao Chen, Wang Pei一de, Lu Yu-mei, et al., Interpretation of Shear-wave Splitting in Datong Area, NorthChina, Canadian Journal of Exploration Geophys., 29,341-351,1993.
[5] 高原、郑斯华、孙勇,唐山地区剪切波分裂和地壳裂隙各向异性,地震学报,17, 283-293, 1995.
[6] 雷军、王培德、姚陈、熊杨武、陈运泰,云南剑川小孔径台网地震记录特征与横波分裂,见:中国地球物理学会编,中国地球物理学会年刊,北京:地震出版社,84,1994.
[7] 李白基,云南禄劝地区地震各向异性的初步分析,见:中国地球物理学会编,中国地球物理学会年刊,北京:地震出版社,184,1994.
[8] 王培德,近震源强地面运动研究,见;[博士论文],国家地震局地球物理研究所, 1987.
[9] Gledhill, K. R., Shear waves recorded on Close-Spaced seimographs: Shear-wave Splitting Results,Canadian Journal of Exploration Geohys., 29,285-298,1993.
[10] 王培德、陈运泰、王鸣,中国西南地区近震源强地面运动特征,北京:地震出版社,1993.
[11] 马殿军,1982年7月3日云南剑川地区Ms5.4级地震,见:张肇诚主编,中国震例,北京:地震出版社,92-108,1987.
[12] 何浩生、何科昭、朱照宇等,云南剑川盆地新构造运动特征与云南高原隆起问题,见:地质矿产部青藏高原地质文集编委会编,青藏高原地质文集(17),北京:地质出版社,103-115,1985.
[13] 刘光勋、李方全、李桂荣,我国滇西北地震活动区的活动构造与应力状态,地震地质,8,1-14,1986.
[14] 马瑾,滇西北发震构造条件及其与鲜水河断裂带的对比,地震地质,10,35-43,1988.
[15] 向宏发、虢顺民、冉勇康等,滇西北地区的现代构造应力场,地震地质,8,15-23,1986.
[16] 周瑞奇、董必献,地震活动性,见:国家地震局地质所和云南省地震局编,滇西北地区地震活动断裂,北京:地质出版社,219-235,1990.
[17] Crampin, S., Booth, D. C., Evans, R.C., Evans, R., Peacock, S., Fletcher, J. B., Changes in shear wave splitting atAnza near the bine of the North palm Springs Earthquake,J. Geophys. Res., 95, 11197-11212, 1990.
[18] Xiong Yang-wu, Yao Chen, Fan Hui-ji, The features of shear wave splitting in Lulong in Northern Chinaand its seismic implications,The fifth international workshop on seismic anisotropy, Canada, Mny. 1992.
[2] Crampin, S., Geological and industrial implications of extensive-dilatancy anisotropy, Nature, 328,491-496,1987
[3] 姚陈、王培德、陈运泰,卢龙地区 S波偏振与上地壳裂隙各向异性,地球物理学报,35, 305-315, 1992。
[4] Yao Chen, Wang Pei一de, Lu Yu-mei, et al., Interpretation of Shear-wave Splitting in Datong Area, NorthChina, Canadian Journal of Exploration Geophys., 29,341-351,1993.
[5] 高原、郑斯华、孙勇,唐山地区剪切波分裂和地壳裂隙各向异性,地震学报,17, 283-293, 1995.
[6] 雷军、王培德、姚陈、熊杨武、陈运泰,云南剑川小孔径台网地震记录特征与横波分裂,见:中国地球物理学会编,中国地球物理学会年刊,北京:地震出版社,84,1994.
[7] 李白基,云南禄劝地区地震各向异性的初步分析,见:中国地球物理学会编,中国地球物理学会年刊,北京:地震出版社,184,1994.
[8] 王培德,近震源强地面运动研究,见;[博士论文],国家地震局地球物理研究所, 1987.
[9] Gledhill, K. R., Shear waves recorded on Close-Spaced seimographs: Shear-wave Splitting Results,Canadian Journal of Exploration Geohys., 29,285-298,1993.
[10] 王培德、陈运泰、王鸣,中国西南地区近震源强地面运动特征,北京:地震出版社,1993.
[11] 马殿军,1982年7月3日云南剑川地区Ms5.4级地震,见:张肇诚主编,中国震例,北京:地震出版社,92-108,1987.
[12] 何浩生、何科昭、朱照宇等,云南剑川盆地新构造运动特征与云南高原隆起问题,见:地质矿产部青藏高原地质文集编委会编,青藏高原地质文集(17),北京:地质出版社,103-115,1985.
[13] 刘光勋、李方全、李桂荣,我国滇西北地震活动区的活动构造与应力状态,地震地质,8,1-14,1986.
[14] 马瑾,滇西北发震构造条件及其与鲜水河断裂带的对比,地震地质,10,35-43,1988.
[15] 向宏发、虢顺民、冉勇康等,滇西北地区的现代构造应力场,地震地质,8,15-23,1986.
[16] 周瑞奇、董必献,地震活动性,见:国家地震局地质所和云南省地震局编,滇西北地区地震活动断裂,北京:地质出版社,219-235,1990.
[17] Crampin, S., Booth, D. C., Evans, R.C., Evans, R., Peacock, S., Fletcher, J. B., Changes in shear wave splitting atAnza near the bine of the North palm Springs Earthquake,J. Geophys. Res., 95, 11197-11212, 1990.
[18] Xiong Yang-wu, Yao Chen, Fan Hui-ji, The features of shear wave splitting in Lulong in Northern Chinaand its seismic implications,The fifth international workshop on seismic anisotropy, Canada, Mny. 1992.
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