结合波形互相关的双差定位方法在2008年汶川地震余震序列中的应用
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摘要
选取了汶川地震主震后的2008年5月12日—2009年8月31日,震级为3.0≤MS≤5.0的余震4 240次.利用波形互相关方法得到其P波到时,用双差定位方法对其进行定位,最终得到了2 441次重新定位的结果.统计定位误差(两倍标准偏差)在E--W方向为0.4 km,N--S方向为0.4 km,垂直方向为0.7 km.定位结果表明,汶川地震的余震深度集中在10—20 km,震中分布与龙门山中央断裂带的走向关系密切.沿龙门山断裂的地震分布具有明显的分段性,西南段呈水平带状分布,东北段接近垂直分布,且在北川附近存在深度突变.这与龙门山断裂的地震在西南段多表现为逆冲,东北段多表现为走滑的现象相吻合.在深度剖面上地震的空间分布存在分立的特征,通过对比前人在此地区浅层的地震剖面资料,发现地震空间分布与已探知的浅部断层有较好的对应关系.
We collected seismic records of 4240 3.0≤MS≤5.0 aftershocks of the 2008 Wenchuan earthquake for the period of 12 May 2008 to 31 August 2009.By using waveform cross-correlation and double-difference method,2441 events of them were relocated.The errors are 0.4 km in horizontal and 0.7 km in vertical direction,respectively.It is found that the depth of aftershocks concentrate in 10—20 km range,and the epicenters distribute close to the strike of the central Longmenshan fault.The aftershock epicenters spread in horizontal belt for southwestern section of the aftershock zone,and in vertical belt for northeastern section.The aftershock depth abruptly change from 20 km to 10 km near Beichuan.This implies that the spatial distribution of aftershocks show different characteristics along Longmenshan fault,confirming the previous viewpoint that the fault is thrust in SW,while strike-slip in NE.Comparison of the aftershock relocation result with the existing shallow seismic exploration profiles reveals that the aftershock belts well match the known shallow geological active faults.
We collected seismic records of 4240 3.0≤MS≤5.0 aftershocks of the 2008 Wenchuan earthquake for the period of 12 May 2008 to 31 August 2009.By using waveform cross-correlation and double-difference method,2441 events of them were relocated.The errors are 0.4 km in horizontal and 0.7 km in vertical direction,respectively.It is found that the depth of aftershocks concentrate in 10—20 km range,and the epicenters distribute close to the strike of the central Longmenshan fault.The aftershock epicenters spread in horizontal belt for southwestern section of the aftershock zone,and in vertical belt for northeastern section.The aftershock depth abruptly change from 20 km to 10 km near Beichuan.This implies that the spatial distribution of aftershocks show different characteristics along Longmenshan fault,confirming the previous viewpoint that the fault is thrust in SW,while strike-slip in NE.Comparison of the aftershock relocation result with the existing shallow seismic exploration profiles reveals that the aftershock belts well match the known shallow geological active faults.
引文
黄媛,吴建平,张天中,张东宁.2008.汶川8.0级大地震及其余震序列重定位研究[J].中国科学:D辑,38(10):1242--1249.
黄媛.2008.结合波形互相关技术的双差算法在地震定位中的应用探讨[J].国际地震动态,(4):29--34.
黄媛,杨建思,张天中.2006.2003年新疆巴楚-伽师地震序列的双差法重新定位研究[J].地球物理学报,49(1):162--169.
黄耘,李清河,张元生,孙业君,沈红会,金淑梅.2008.江苏及邻区地震重新定位和构造特征分析[J].地球物理学报,51(1):175--185.
宋鸿彪.1994.龙门山造山带地质和地球物理资料的综合解释[J].成都理工学院学报,21(2):79--88.
吴建平,黄媛,张天中,明跃红,房立华.2009.汶川MS8.0级地震余震分布及周边区域P波三维速度结构研究[J].地球物理学报,52(2):320--328.
徐旭辉.1993.川西龙门山前缘地质地球物理解释[J].石油实验地质,15(1):60--73.
杨智娴,陈运泰,郑月军,于湘伟.2003.双差地震定位算法在我国中西部地区地震精确定位中的应用[J].中国科学:D辑,46(增刊):181--188.
杨智娴,陈运泰.2004.用双差地震定位法再次精确测定1998年张北-尚义地震序列的震源参数[J].地震学报,26(2):115--120.
张瑞青,吴庆举,李永华,丁志峰,曾融生.2008.汶川中强余震震源深度的确定及其意义[J].中国科学:D辑,38(10):1234--1241.
赵翠萍.2006.1997-2003年伽师震源区特征的地震学方法研究[D].北京:中国地震局地球物理研究所:1--166.
赵珠,范军,郑斯华,长谷川昭,堀内茂木.1997.龙门山断裂带地壳速度结构和震源位置的精确测定[J].地震学报,19(6):615--622.
郑钰,杨建思.2008.双差算法的剖析及参数对定位的影响[J].地震地磁观测与研究,29(3):85--93.
Hauksson E,Shearer P.2005.Southern California hypocenter relocation with waveformcross-correlation,part1:Re-sults using the double-difference method[J].Bull Seism Soc Amer,95(3):896--903.
Richards P G,Waldhauser F,Schaff D,Kim W Y.2006.The applicability of modern methods of earthquake location.Pure Appl Geophys,163(2--3):351--372.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Waldhauser F,Schaff D P.2008.Large-scale relocation of two decades of Northern California seismicity using cross-cor-relation and double-difference methods[J].J Geophys Res,113,B08311,doi:10.1029/2007JB005479.
Yang Z X,Waldhauser F,Chen Y T,Richards P G.2005.Double-difference relocation of earthquakesin central-westernChina,1992-1999[J].Journal of Seismology,9(2):241--264.
黄媛.2008.结合波形互相关技术的双差算法在地震定位中的应用探讨[J].国际地震动态,(4):29--34.
黄媛,杨建思,张天中.2006.2003年新疆巴楚-伽师地震序列的双差法重新定位研究[J].地球物理学报,49(1):162--169.
黄耘,李清河,张元生,孙业君,沈红会,金淑梅.2008.江苏及邻区地震重新定位和构造特征分析[J].地球物理学报,51(1):175--185.
宋鸿彪.1994.龙门山造山带地质和地球物理资料的综合解释[J].成都理工学院学报,21(2):79--88.
吴建平,黄媛,张天中,明跃红,房立华.2009.汶川MS8.0级地震余震分布及周边区域P波三维速度结构研究[J].地球物理学报,52(2):320--328.
徐旭辉.1993.川西龙门山前缘地质地球物理解释[J].石油实验地质,15(1):60--73.
杨智娴,陈运泰,郑月军,于湘伟.2003.双差地震定位算法在我国中西部地区地震精确定位中的应用[J].中国科学:D辑,46(增刊):181--188.
杨智娴,陈运泰.2004.用双差地震定位法再次精确测定1998年张北-尚义地震序列的震源参数[J].地震学报,26(2):115--120.
张瑞青,吴庆举,李永华,丁志峰,曾融生.2008.汶川中强余震震源深度的确定及其意义[J].中国科学:D辑,38(10):1234--1241.
赵翠萍.2006.1997-2003年伽师震源区特征的地震学方法研究[D].北京:中国地震局地球物理研究所:1--166.
赵珠,范军,郑斯华,长谷川昭,堀内茂木.1997.龙门山断裂带地壳速度结构和震源位置的精确测定[J].地震学报,19(6):615--622.
郑钰,杨建思.2008.双差算法的剖析及参数对定位的影响[J].地震地磁观测与研究,29(3):85--93.
Hauksson E,Shearer P.2005.Southern California hypocenter relocation with waveformcross-correlation,part1:Re-sults using the double-difference method[J].Bull Seism Soc Amer,95(3):896--903.
Richards P G,Waldhauser F,Schaff D,Kim W Y.2006.The applicability of modern methods of earthquake location.Pure Appl Geophys,163(2--3):351--372.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Waldhauser F,Schaff D P.2008.Large-scale relocation of two decades of Northern California seismicity using cross-cor-relation and double-difference methods[J].J Geophys Res,113,B08311,doi:10.1029/2007JB005479.
Yang Z X,Waldhauser F,Chen Y T,Richards P G.2005.Double-difference relocation of earthquakesin central-westernChina,1992-1999[J].Journal of Seismology,9(2):241--264.
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