2011年3月11日日本宫城M_W9.1地震的预滑与黏滑震相研究
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摘要
实验室内的岩石黏滑实验表明:黏滑错动过程一般可分为预滑、黏滑和止滑三个阶段,其中黏滑过程往往不是一次单点错动过程,而是由多次黏滑错动过程组成,表现出在断层的不同部位多点黏滑错动的特征。2011年3月11日日本宫城近海发生了M_W9.1大地震。对该地震在全球数字地震仪台网(GSN)的波形记录做了分析,在ERM台(Δ=3.8°)记录的Pn震相前约125.5 s处识别出预滑错动震相Xp;在GSN 98个台的长周期波形记录上识别出三次同震黏滑错动过程中激发出的三个同震黏滑错动震相Xs1、Xs2和Xs3,以及止滑过程中激发出的止滑面波震相XsQ和XsR。根据黏滑实验和观测结果,我们认为ERM台所处的地块在主震前约69.1 s时发生了一次临震预滑错动,激发出了预滑错动震相Xp。主震发生后与弹性破裂过程同时发生了第一次黏滑错动,激发出了黏滑错动震相Xs1;在弹性破裂开始后约27.5 s时发生了第二次黏滑错动,激发出了黏滑错动震相Xs2;在弹性破裂开始后约71.0 s时发生了第三次黏滑错动,激发出了黏滑错动震相Xs3;在弹性破裂开始后约93.1 s时黏滑错动幅度达到峰值Xsm。之后进入止滑阶段,止滑过程激发出了勒夫型长周期面波止滑震相XsQ和瑞雷型长周期面波止滑震相XsR。根据XsQ和XsR震相的周期普遍大于75 s的特征,我们认为XsQ和XsR可能是地幔内传播的面波,并给出XsQ和XsR面波的走时关系。根据主震发生后同震伴随有三个子黏滑错动过程的观测证据,认为此次M_W9.1大地震可能是黏滑错动和弹性破裂共同作用的结果。从地震记录图上识别出Xp震相有助于认识主震前的预滑错动过程,且有一定的前兆意义。研究Xs震相以及XsQ和XsR震相有助于认识同震黏滑错动过程并预判震灾损失。
The results of indoor rock stick-slip experiments show that one stick-slip dislocation process often includes three stages: pre-slip, stick-slip, and stop-slip. In addition, the stick-slip process is not a single point dislocation process; rather, it comprises many stick-slip dislocation processes, showing the characteristic of multi-point stick-slip dislocation in different parts of the fault. An M_W9.1 earthquake occurred near the coast of Tohoku, Japan, on March 11, 2011. After analyzing the waveform records from the Global Seismographic Network(GSN), we identified the Xp phase about 125.5 s prior to the Pn phase from the records of the ERM station(Δ=3.8°). We then identified three stick-slip dislocation phases(Xs1, Xs2, and Xs3) and two stop-slip phases(XsQ and XsR) from the records of 98 stations in GSN. According to the results of stick-slip experiments and observation, we inferred that at the block where the ERM station was located, an impending pre-slip dislocation occurred about 69.1 s prior to the main shock, which excited the Xp phase. Following the main shock, the first stick-slip dislocation occurred during the elastic rupture process. Then, the stick-slip dislocation phase Xs1 was excited. About 27.5 s after the elastic rupture, the second stick-slip dislocation occurred, and the stick-slip dislocation phase Xs2 was excited. About 71.0 s after the elastic rupture, the third stick-slip dislocation occurred, and the stick-slip dislocation phase Xs3 was excited. About 93.1 s after the elastic rupture, the stick-slip dislocation amplitude reached its peak value of Xsm, then entered the stop-slip stage, wherein the stop-slip phase XsQ and XsR were excited. According to the fact that the periods of XsQ and XsR phases are generally greater than 75 s, we suggested that the XsQ and XsR phases may be the surface wave propagating through the mantle. The travel time relationship between XsQ and XsR phases were given. According to the observed evidence that the main shock was accompanied by three sub-stick-slip dislocation events, we suggested that the M_W9.1 earthquake may have resulted from the cooperation of elastic rupture and stick-slip dislocation. Identifying the Xp phase from seismic records is helpful in understanding the pre-slip dislocation process before the main shock, with certain precursory significance. Studying the Xs, XsQ, and XsR phases will be helpful in understanding the coseismic stick-slip dislocation processes, and in judging the earthquake disaster loss.
The results of indoor rock stick-slip experiments show that one stick-slip dislocation process often includes three stages: pre-slip, stick-slip, and stop-slip. In addition, the stick-slip process is not a single point dislocation process; rather, it comprises many stick-slip dislocation processes, showing the characteristic of multi-point stick-slip dislocation in different parts of the fault. An M_W9.1 earthquake occurred near the coast of Tohoku, Japan, on March 11, 2011. After analyzing the waveform records from the Global Seismographic Network(GSN), we identified the Xp phase about 125.5 s prior to the Pn phase from the records of the ERM station(Δ=3.8°). We then identified three stick-slip dislocation phases(Xs1, Xs2, and Xs3) and two stop-slip phases(XsQ and XsR) from the records of 98 stations in GSN. According to the results of stick-slip experiments and observation, we inferred that at the block where the ERM station was located, an impending pre-slip dislocation occurred about 69.1 s prior to the main shock, which excited the Xp phase. Following the main shock, the first stick-slip dislocation occurred during the elastic rupture process. Then, the stick-slip dislocation phase Xs1 was excited. About 27.5 s after the elastic rupture, the second stick-slip dislocation occurred, and the stick-slip dislocation phase Xs2 was excited. About 71.0 s after the elastic rupture, the third stick-slip dislocation occurred, and the stick-slip dislocation phase Xs3 was excited. About 93.1 s after the elastic rupture, the stick-slip dislocation amplitude reached its peak value of Xsm, then entered the stop-slip stage, wherein the stop-slip phase XsQ and XsR were excited. According to the fact that the periods of XsQ and XsR phases are generally greater than 75 s, we suggested that the XsQ and XsR phases may be the surface wave propagating through the mantle. The travel time relationship between XsQ and XsR phases were given. According to the observed evidence that the main shock was accompanied by three sub-stick-slip dislocation events, we suggested that the M_W9.1 earthquake may have resulted from the cooperation of elastic rupture and stick-slip dislocation. Identifying the Xp phase from seismic records is helpful in understanding the pre-slip dislocation process before the main shock, with certain precursory significance. Studying the Xs, XsQ, and XsR phases will be helpful in understanding the coseismic stick-slip dislocation processes, and in judging the earthquake disaster loss.
引文
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[8]李普春,刘力强,郭玲莉,等.黏滑过程中的多点错动[J].地震地质,2013,35(1):125-137.LI Puchun,LIU Liqiang,GUO Lingli,et al.Multi-point Dislocation in Stick-Slip Process[J].Seismology and Geology,2013,35(1):125-137.
[9]BENIOFF H,PRESS F.Progress Report on Long Period Seismographs[J].Geophysical Journal International,1958,1(3):208-215.
[10]KENNETT,B L N.IASPEI 1991地震走时表[M].陈培善,编译.北京:地震出版社,1993:108-130.KENNETT,B L N.IASPEI 1991Seismological Tables[M].CHEN Peishan,Tr.Beijing:Seismological Press,1993:108-130.
[11]许健生,隗永刚,张淑珍.Pdif波在中国CDSN台站的运动学特征[J].地震工程学报,2013,35(3):610-617.XU Jiansheng,WEI Yonggang,ZHANG Shuzhen.The Kinematic Characteristics of Pdif-Waves at CDSN Stations[J].China Earthquake Engineering Journal,2013,35(3):610-617.
[12]JEFFREYS H,BULLEN K E.Seismological Tables London[R].British Association for the Advancement of Science,1940.
[13]ZHANG Y,XU L S,CHEN Y T.Fast Rupture Process Inversion of the 11March 2011Earthquake near the East Coast of Honshu,Japan_[2011-03-11]http//ddsep.cea-igp.ac.cn/rp/2011.
[2]冯德益,潘琴龙,郑斯华,等.长周期形变波及其所反应的短期和临震地震前兆[J].地震学报,1984,6(1):41-57.FENG Deyi,PAN Qinlon,ZHENG Sihua,et al.Long-period Deformational Waves and Short-term and Imminent Earthquake Precursors[J].Acta Seismologica Sinica,1984,6(1):41-57.
[3]高金哲,吕政,张洪艳,等.地震前驱波观测与研究进展[J].华南地震,2005,25(1):53-58.GAO Jinzhe,LZheng,ZHANG Hongyan,et al.Progress in the Observation and Research on Earthquake Precursor Wave[J].South China Journal of Seismology,2005,25(1):53-58.
[4]BRACE W F,BYERLEE J D.Stick-Slip as a Mechanism for Earthquakes[J].Science,1966,153(3739):990-992.
[5]BYERLEE J D,SUMMERS R.Stable Sliding Preceding StickSlip on Fault Surfaces in Granite at High Pressure[J].Pure and Applied Geophysics,1975,113(1):63-68.
[6]车用太,鱼金子,张淑亮,等.山西朔州井水位的“前驱波”记录及其讨论[J].地震学报,2002,24(2):210-216.CHE Yongtai,YU Jinzi,ZHANG Shuliang,et al.The Records of Water Level“Precursors”and Their Discussion in Well Shuozhou,Shanxi Province[J].Acta Seismologica Sinica,2002,24(2):210-216.
[7]郭增建,秦保燕.大震前予位移的讨论[J].西北地震学报,1979,1(2):34-40.GUO Zengjian,QIN Baoyan.A Discussion on Pre-slipping prior to Great Earthquakes[J].Northwestern Seismological Journal,1979,1(2):34-40.
[8]李普春,刘力强,郭玲莉,等.黏滑过程中的多点错动[J].地震地质,2013,35(1):125-137.LI Puchun,LIU Liqiang,GUO Lingli,et al.Multi-point Dislocation in Stick-Slip Process[J].Seismology and Geology,2013,35(1):125-137.
[9]BENIOFF H,PRESS F.Progress Report on Long Period Seismographs[J].Geophysical Journal International,1958,1(3):208-215.
[10]KENNETT,B L N.IASPEI 1991地震走时表[M].陈培善,编译.北京:地震出版社,1993:108-130.KENNETT,B L N.IASPEI 1991Seismological Tables[M].CHEN Peishan,Tr.Beijing:Seismological Press,1993:108-130.
[11]许健生,隗永刚,张淑珍.Pdif波在中国CDSN台站的运动学特征[J].地震工程学报,2013,35(3):610-617.XU Jiansheng,WEI Yonggang,ZHANG Shuzhen.The Kinematic Characteristics of Pdif-Waves at CDSN Stations[J].China Earthquake Engineering Journal,2013,35(3):610-617.
[12]JEFFREYS H,BULLEN K E.Seismological Tables London[R].British Association for the Advancement of Science,1940.
[13]ZHANG Y,XU L S,CHEN Y T.Fast Rupture Process Inversion of the 11March 2011Earthquake near the East Coast of Honshu,Japan_[2011-03-11]http//ddsep.cea-igp.ac.cn/rp/2011.