安庆4.8级地震的余震S波分裂研究
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摘要
利用安徽数字地震台网安庆台记录的地震波形资料,运行Matlap S波分裂程序,对2011年1月19日安徽安庆4.8级地震的余震序列开展S波分裂研究。结果表明,快S波偏振方向有两个优势取向,分别为N73°E和N94°E,初步判断为区域应力场导致的EDA裂隙系各向异性结果。其中快S波N73°E偏振方向与区域应力场的主压应力方向N74°E基本相同,而快S波N94°E偏振方向稍有偏差,可能是由于4.8级主震产生的应力扰动引起的。慢S波延迟时间在0.82～10.92范围内变化,平均为2.84,主震后,延迟时间明显下降,可能反映了震后应力的释放过程,而几次较大余震前则处于上升高值状态,可能反映了较大余震前的应力积累过程。
Using Anqing M4.8 earthquake sequence data recorded by Anqing station of Anhui Digital Seismic Network,by matlap shear wave splitting order,making shear wave splitting study on aftershocks sequence of M4.8 Anqing Earthquake on January 19 2011.The results show that there are two preferred polarization directions from the fast shear wave.N73°E and N94°E respectively,which were resulted from the anisotropy of the stress-induced cracks(EDA).The polarization direction for the fast shear wave N73°E was in accord with principal compression stress axis N74°E of the source stress field.But the polarization direction for the fast shear wave N94°E was different,which may be due to the stress disturbance imposed by the M4.8 mainshock on regional background stress field.The time delay of shear wave splitting from 0.82ms/km to 10.92ms/km and the average of the whole process was 2.84ms/km.After mainshock,the time delay of shear wave splitting dropped apparently,which may reflect the release of the principal compression stress.The time delay of shear wave splitting rose with higher values of state before some larger aftershock,which may reflect the accumulation of the principal compression stress before shocks.
Using Anqing M4.8 earthquake sequence data recorded by Anqing station of Anhui Digital Seismic Network,by matlap shear wave splitting order,making shear wave splitting study on aftershocks sequence of M4.8 Anqing Earthquake on January 19 2011.The results show that there are two preferred polarization directions from the fast shear wave.N73°E and N94°E respectively,which were resulted from the anisotropy of the stress-induced cracks(EDA).The polarization direction for the fast shear wave N73°E was in accord with principal compression stress axis N74°E of the source stress field.But the polarization direction for the fast shear wave N94°E was different,which may be due to the stress disturbance imposed by the M4.8 mainshock on regional background stress field.The time delay of shear wave splitting from 0.82ms/km to 10.92ms/km and the average of the whole process was 2.84ms/km.After mainshock,the time delay of shear wave splitting dropped apparently,which may reflect the release of the principal compression stress.The time delay of shear wave splitting rose with higher values of state before some larger aftershock,which may reflect the accumulation of the principal compression stress before shocks.
引文
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[10]孙业君,周云好.2011年1月19日安徽安庆M4.8地震的震源机制[J].国际地震动态,2011,387(3):27-28.
[11]郑先进,刘东旺.2010.安徽地区应力场分区特征及中强震前震源机制的一致性研究[J].华北地震科学,28(1):16-20.
[2]Aki K,Defazio T,Reasenberg P,et a1.1970.An active experiment with earthquake fault for an estimationof the in situstress[J].Bull Seism Soc Amer,60:1315～1336.
[3]Crampin S.1978.Seismic wave propagation through a cracked solid:polarization as possible dilatancydiagnostic[J].Geophys J R astr Soc,53:467～496.
[4]高原,郑斯华.1994.唐山地区剪切波分裂研究(Ⅱ)-相关函数分析法[J].中国地震,10(9):22～32.
[5]Crampin S,Evans R,Ucer B.1985.Analysis of records of local earthquakes:The Turkish DulatancyProjects(TDP1 and TDP2)[J].Geophys J,83:1-16.
[6]Crampin S and Booth D C.1985.Shear-wave polarizations near the North Anatohan fault,Ⅱ.Interpretanion interns of earth-induced anisotropy[J].Geophys J.83.75-92.
[7]倪晓寅.2007年顺昌M4.9地震余震的剪切波分裂现象[J].地震地磁观测与研究,2009,30(6):1-5
[8]黄腾浪.新丰江地震S波偏振的初步研究[J].华南地震,2001,21(4):22-26.
[9]顾浩鼎.前兆震群和S波偏振[J].地震学报,1980,2(4):342-355.
[10]孙业君,周云好.2011年1月19日安徽安庆M4.8地震的震源机制[J].国际地震动态,2011,387(3):27-28.
[11]郑先进,刘东旺.2010.安徽地区应力场分区特征及中强震前震源机制的一致性研究[J].华北地震科学,28(1):16-20.
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