利用GPS资料反演汶川Mw 7.9级地震滑动分布
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摘要
2008年5月12日,青藏高原东缘龙门山断裂带发生Mw7.9级汶川地震,该地震使得北川—映秀断裂、灌县—江油断裂带发生了同震破裂。本文主要利用"中国地壳运动观测网络"项目组提供的GPS同震位移资料,采用基于敏感度迭代拟合法(SBIF)及分段发震断层模型,分别应用均匀半空间和分层地壳结构两种方法反演分析该次地震的精细同震滑动分布。结果表明:①SBIF反演方法应用于相对较小的GPS数据集仍然可以获得理想的同震滑动分布;②采用考虑分层地壳结构模型的反演结果整体上要优于均匀半空间模型的结果;③同震滑动主要发生在10～19km深度以上,且存在五个滑动峰值区域及北川断裂南西端存在明显的深部滑动区,与震后野外考察结果及余震分布相吻合,同时能够较好地解释GPS观测数据;④青川断裂存在明显的右旋走滑分量,其平均滑动量为1.99m,北川断裂主要发生逆冲滑动,平均滑动量为3.35m,灌县断裂的平均滑动量为0.65m;⑤反演得到的地震矩为8.74×1020Nm(Mw7.90),与地震学结果吻合。
On 2008 May 12,The Mw 7.9 Wenchuan earthquake along the Longmenshan Fault zone,occured at the eastern margin of the Tibetan Plateau,rupturing the Beichuan-Yingxiu and Guanxian-Jiangyou faults.Based on the segmenting fault model,we derive the fine slip distribution by utilizing a sensitivity-based iterative fitting method(SBIF) to GPS datasets mainly from the Crustal Movement Observation Network of China(CMONOC),with the two models of the homogeneous half space and the stratified crustal structure.The results show:①The coseismic slip distribution still can be inversed reasonably by applying a sensitivity-based iterative fitting method to the relatively minor GPS datasets;② The inversion results considering the stratified crustal structure are superior to them from the homogeneous,half space in the mass;③ The coseismic slip is concentrated to above the 10～19 km depth.There exist five slip peak zones and obvious slip distribution at the lower part of SW Beichuan fault,in line with the field investigations and the aftershocks,also can resolve the GPS observations better;④ The Qingchuan fault experienced distinct right-lateral slip,and the magnitude of mean slip is 1.99 m.However,the Beichuan fault mainly experienced thrust slip,and the magnitude of mean slip is 3.35 m.The magnitude of mean slip for Guanxian fault is 0.65 m;⑤ The inversed moment is 8.74×1020Nm(Mw 7.90),consistent with seismic estimates.
On 2008 May 12,The Mw 7.9 Wenchuan earthquake along the Longmenshan Fault zone,occured at the eastern margin of the Tibetan Plateau,rupturing the Beichuan-Yingxiu and Guanxian-Jiangyou faults.Based on the segmenting fault model,we derive the fine slip distribution by utilizing a sensitivity-based iterative fitting method(SBIF) to GPS datasets mainly from the Crustal Movement Observation Network of China(CMONOC),with the two models of the homogeneous half space and the stratified crustal structure.The results show:①The coseismic slip distribution still can be inversed reasonably by applying a sensitivity-based iterative fitting method to the relatively minor GPS datasets;② The inversion results considering the stratified crustal structure are superior to them from the homogeneous,half space in the mass;③ The coseismic slip is concentrated to above the 10～19 km depth.There exist five slip peak zones and obvious slip distribution at the lower part of SW Beichuan fault,in line with the field investigations and the aftershocks,also can resolve the GPS observations better;④ The Qingchuan fault experienced distinct right-lateral slip,and the magnitude of mean slip is 1.99 m.However,the Beichuan fault mainly experienced thrust slip,and the magnitude of mean slip is 3.35 m.The magnitude of mean slip for Guanxian fault is 0.65 m;⑤ The inversed moment is 8.74×1020Nm(Mw 7.90),consistent with seismic estimates.
引文
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[17]ZHAO Zhu,FANJun,ZHENG Sihua,et al.The Crustal Velocity Structure of Longmenshan Fault Belt and the Fine Revised of Hypocentral Location[J].Acta Seis-mologica Sinica,1997,19(6):615-622.(赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,1997,19(6):615-622.)
[18]WANG Chunyong,MOONEY W D,WANG Xili,et al.Study on3-D Velocity Structure of Crust and Upper Man-tle in Sichuan-Yunnan Region,China[J].Acta Seismolog-ica Snica,2002,24(1):1-16.(王椿镛,Mooney W D,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.)
[19]WANG Y.Heart Flow Pattern and Lateral Variations of Lithosphere Strength in China Mainland:Constraints onActive Deformation[J].Physics of the Earth and Planeta-ry Interiors,2001,126:121-146.
[20]ZHANG Chaojun,CAO Jianling,SHI Yaolin.The Vis-cosity Research of Lower Crust of the Qinghai-Tibet Plat-eau from Postseismic Deformation[J].Science in China:D,2008,38(10):1250-1257.(张晁军,曹建玲,石耀霖.从震后形变探讨青藏高原下地壳黏滞系数[J].中国科学:D辑,2008,38(10):1250-1257.)
[2]CMONOC.Coseismic Signals of the2008Ms8.0Wenchuan Earthquake Determined with GPS[J].Science in China:D,2008,38(10):1195-1206.(国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川Ms8.0级地震的同震位移场[J].中国科学:D辑,2008,38(10):1195-1206.)
[3]WANG Q,QI AO X,WANG M,et al.GPS-derived Co-seismic Deformation Associated with the12May2008Wenchuan Earthquake[C]//AGU Fall Meeting2008Eos Trans89(53).San Francisco:American Geophysical U-nion,2008.
[4]HASHI MOTO M,ENOMOTO M,FUKUSHI MA Y,et al.Interferograms of Coseismic Deformation fromthe May12,2008,Sichuan,China,Earthquake obtained by ALOS/PALSAR[C]//AGU Fall Meeting2008Eos Trans,89(53).San Francisco:American Geophysical Union,2008.
[5]GE L,ZHANG K,NG A,et al.Near real-ti me radarinter-ferometric mapping of the12May2008Ms8.0Wenchuan Earthquake in China[C]//AGU Fall Meeting2008Eos Trans,89(53).San Francisco:American Geophysical U-nion,2008.
[6]SUN J,SHEN Z,XU X,et al.Constraining the2008Wenchuan,China Earthquake Rupture Model Using SAR Interferometry Data and an Angular Dislocation Model[C]//AGU Fall Meeting2008Eos Trans,89(53).San Francisco:American Geophysical Union,2008.
[7]LI Zhenhong,ERIC J,TI M WRIGHT F,et al.Fault Trace and Slipin the2008Mw7.9Sichuan,China Earth-quake fromInSARand GPS Observations[C]//AGU Fall Meeting2008Eos Trans,89(53).San Francisco:American Geophysical Union,2008.
[8]PARSONS T,CHENJi,KIRBY E.Stress Changes from the2008Wenchuan Earthquake and Increased Hazard in the Sichuan Basin[J].Nature,2008(454):509-510.
[9]ZHANG Yong,FENG Wangpeng,XU Liheng,et al.The Ti me-spatial Rupture Process of the2008Large Wenchuan Earthquake[J].Science in China:D,2008,38(10):1186-1194.(张勇,冯万鹏,许力生,等.2008年汶川大地震的时空破裂过程[J].中国科学:D辑,2008,38(10):1186-1194.)
[10]WANG Wei min,YAOZhenxing.Reissues for the Rupture process of the Ms8.0Wenchuan Earthquake[R/OL].[2009-02-10].http://www.csi.ac.cn/sichuan/si-chuan080512-110.ht m.(王卫民,姚振兴.再谈汶川8.0级地震震源破裂过程[R/OL].[2009-02-10].http://www.csi.ac.cn/sichuan/sichuan080512-110.ht m.)
[11]OKADA Y.Internal Deformation due to Shear and Ten-sile Faults in a Half-space[J].Bulletin of the Seismologi-cal Society of America.1992,82(2):1018-1040.
[12]WANG R,XI A Y,GROSSER H,et al.The2003Bam(SE Iran)Earthquake,Precise Source Parameters from Satellite Radar Interferometry[J].GJI,2004(159):917-922.
[13]WANG Rongjiang,MOTAGH M,WALTER T R.In-version of Slip Distribution from Co-seismic Deformation Data by a Sensitivity-based Iterative Fitting Method[C]//EGU General Assembly2008.Vienna:EGU,2008.
[14]HUANG Yuan,WU Jianping,ZHANG Tianzhong,et al.the Relocation Research of the8.0Large Wenchuan Earthquake and the Aftershock Sequences[J].Science in China:D,2008,38(10):1242-1249.(黄媛,吴建平,张天中,张东宁.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,2008,38(10):1242-1249.)
[15]SONG Hongbiao.The Comprehensive Interpretation of Geological and Geophysical Data in the Orogenic Belt of Longmen Mountains,China[J].Journal of Chengdu Uni-versity of Technology,1994,21(2):79-88.(宋鸿彪.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,1994,21(2):79-88.)
[16]XU Xi wei,WEN Xueze,CHEN Guihua,et al.The Foundation and Tectonic Significance of Longriba Fault Belt in Bayankara Block[J].Science in China:D,2008,38(10):1242-1249.(徐锡伟,闻学泽,陈桂华,等.巴颜喀拉地块龙日坝断裂带的发现及其大地构造意义[J].中国科学:D辑,2008,38(7):785-796.)
[17]ZHAO Zhu,FANJun,ZHENG Sihua,et al.The Crustal Velocity Structure of Longmenshan Fault Belt and the Fine Revised of Hypocentral Location[J].Acta Seis-mologica Sinica,1997,19(6):615-622.(赵珠,范军,郑斯华,等.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,1997,19(6):615-622.)
[18]WANG Chunyong,MOONEY W D,WANG Xili,et al.Study on3-D Velocity Structure of Crust and Upper Man-tle in Sichuan-Yunnan Region,China[J].Acta Seismolog-ica Snica,2002,24(1):1-16.(王椿镛,Mooney W D,王溪莉,等.川滇地区地壳上地幔三维速度结构研究[J].地震学报,2002,24(1):1-16.)
[19]WANG Y.Heart Flow Pattern and Lateral Variations of Lithosphere Strength in China Mainland:Constraints onActive Deformation[J].Physics of the Earth and Planeta-ry Interiors,2001,126:121-146.
[20]ZHANG Chaojun,CAO Jianling,SHI Yaolin.The Vis-cosity Research of Lower Crust of the Qinghai-Tibet Plat-eau from Postseismic Deformation[J].Science in China:D,2008,38(10):1250-1257.(张晁军,曹建玲,石耀霖.从震后形变探讨青藏高原下地壳黏滞系数[J].中国科学:D辑,2008,38(10):1250-1257.)
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