汶川大地震震后重力变化和形变的黏弹分层模拟
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摘要
基于有限矩形位错理论及陈运泰等、JiChen等通过地震波反演的断层模型,结合研究区地壳—上地幔平均波速分层结构,利用PSGRN/PSCMP软件模拟计算了黏弹分层半空间中汶川地震(MS8.0)产生的同震及其震后地表形变和重力变化,同时给出了震后形变和重力变化的年变化率.模拟结果表明,同震形变和重力变化显示出发震断层倾滑逆冲兼具右旋走滑综合特征;其变化主要发生于断层在地表的投影区附近,震后地表重力变化和形变量均不断增大,影响的范围也不断扩张;震后50a间近场年均形变量可达10mm,年均重力变化量可达2×10-8m/s2,而远场年均形变量一般低于2mm,年均重力变化量一般低于0.4×10-8m/s2;形变和重力变化在震后200a内变化较为显著,变化率逐渐减小,水平位移在400a后基本稳定不变,垂直位移、重力变化和大地水准面变化在800a后基本稳定不变.
Using the PSGRN/PSCMP software and the fault model used in seismic wave inversion offered by Chen Yuntai et al and Ji Chen et al, based on the finite rectangular dislocation theory and local layered wave velocity structure of the crust-upper-mantle, surface co- and post-seismic gravity change, deformation and geoid change caused by the MS8.0 Wenchuan earthquake are simulated, and the annual variation rate is also computed. The simulation results indicate that: the co-seismic gravity change and deformation show that the earthquake fault is of the characteristics of thrusting and right-lateral strike-slip. The gravity change and deformation mostly occur on the surface of the fault projection plan, and are increasing after the earthquake, with the influence extent being expanding. The annual average near-field deformation can reach to 10 mm during the 50 years after the earthquake, and the annual average gravity change is 2×10-8 m/s2. To the far field, these annual variation are less than 2 mm and 0.4×10-8 m/s2, respectively. The post-seismic deformation and gravity change increase significantly during the first 200 years. The change rate becomes smaller and smaller. Horizontal displacements will come to be stable 400 years later. Vertical displacement, geoid and gravity change will exist until 800 years after the earthquake.
Using the PSGRN/PSCMP software and the fault model used in seismic wave inversion offered by Chen Yuntai et al and Ji Chen et al, based on the finite rectangular dislocation theory and local layered wave velocity structure of the crust-upper-mantle, surface co- and post-seismic gravity change, deformation and geoid change caused by the MS8.0 Wenchuan earthquake are simulated, and the annual variation rate is also computed. The simulation results indicate that: the co-seismic gravity change and deformation show that the earthquake fault is of the characteristics of thrusting and right-lateral strike-slip. The gravity change and deformation mostly occur on the surface of the fault projection plan, and are increasing after the earthquake, with the influence extent being expanding. The annual average near-field deformation can reach to 10 mm during the 50 years after the earthquake, and the annual average gravity change is 2×10-8 m/s2. To the far field, these annual variation are less than 2 mm and 0.4×10-8 m/s2, respectively. The post-seismic deformation and gravity change increase significantly during the first 200 years. The change rate becomes smaller and smaller. Horizontal displacements will come to be stable 400 years later. Vertical displacement, geoid and gravity change will exist until 800 years after the earthquake.
引文
①王琪等.2008.汶川8级地震后震区GPS应急观测报告.
②李辉等.2008.汶川8级地震后震区重力应急观测报告.
陈国光,许凤桔,周荣军,徐杰,周本刚,黎小刚,叶友青.2007.龙门山断裂带晚第四纪活动性分段的初步研究[J].地震地质,29(3):657--673.
陈学波,吴跃强,杜平山,李金森,吴玉荣,蒋国芳,赵静娴.1988.龙门山构造带两侧地壳速度结构特征[G]∥中国大陆深部构造的研究与进展.北京:地震出版社:97--113.
陈运泰,许力生,张勇,杜海林,冯万鹏,刘超,李春来,张红霞.2008.2008年5月12日汶川特大地震震源特性分析报告[EB/OL].[2008-05-26].http:∥www.csi.ac.cn/sichuan/.
崔作舟,陈纪平,吴苓.1996.花石峡—邵阳深部地壳的结构和构造[M].北京:地质出版社:49--168.
邓明莉,孙和平,徐建桥.2008.GPS数据约束的昆仑MS8.1地震断层的分段模型[J].大地测量与地球动力学,28(4):31--37.
李传友,宋方敏,冉勇康.2004.龙门山断裂带北段晚第四纪活动性讨论[J].地震地质,26(2):248--258.
李国和,王思敬,尚彦军,张强.2000.川滇交界地区地壳结构及现代地壳活动模式[J].地质力学学报,6(2):82--91.
申重阳,李辉,谈洪波.2008.汶川8.0级地震同震重力与形变效应模拟[J].大地测量与地球动力学,28(5):6--12.
孙文科.2008.地震火山活动产生重力变化的理论与观测研究的进展及现状[J].大地测量与地球动力学,4:44--53.
谭凯,李杰,王琪.2007.大地测量约束下的阿尔泰岩石圈流变结构[J].地球物理学报,50(6):1713--1718.
谈洪波,申重阳,李辉.2008.断层位错引起的地表重力变化特征研究[J].大地测量与地球动力学,28(4):54--62.
滕吉文,白登海,杨辉,闫雅芬,张洪双,张永谦,阮小敏.2008.2008汶川MS8.0级地震发生的深层过程和动力学响应[J].地球物理学报,51(5):1385--1402.
汪汉胜.1999.黏弹负荷形变理论的应用[D].武汉:中国科学院测量与地球物理研究所:8--9.
王椿镛,韩渭宾,吴建平,楼海,白志明.2003.松潘—甘孜造山带地壳速度结[J].地震学报,25(3):229--241.
吴建平,明跃红,王椿镛.2006.川滇地区速度结构的区域地震波形反演研究[J].地球物理学报,49(5):1369--1376.
邢乐林,李辉,懂正瑶,何志堂,刘少明,谈洪波.2008.成都地震基准台重复绝对重力测量结果分析[J].大地测量与地球动力学,28(6):38--42.
袁旭东.2007.中国三大震例同震形变的研究[D].武汉:中国科学院测量与地球物理研究所:39--41.
赵珠,范军,郑斯华.1997.龙门山断裂带地壳速度结构和震源位置的精确修定[J].地震学报,19(6):615--622.
周荣军,李勇,Alexander L Densmore,Michael A Ellis,何玉林,王凤林,黎小刚.2006.青藏高原东缘活动构造[J].矿物岩石,26(2):40--51.
Alexander L Densmore,Michael A.2007.Active tectonics of the Beichuan and Pengguan faults at the eastern margin ofthe Tibetan Plateau[J].Tectonics,26,TC4005:1-17.
Huang J L.2007.Lithospheric structure and its relationship to seismic and volcanic activity in southwest China[J].JGeophys Res,107(BIO2255):1--14.
Ji Chen,UCSB,Hayes Gavin.2008.NEIC,Preli minary Result of the May12,2008MW7.9Eastern Sichuan,ChinaEarthquake.[2008-05].http:∥earthquake.usgs.gov/eqcenter/eqinthenews/us2008ryan/.
Longman I M.1963.A Green’s functionfor determiningthe deforation of the Earth under surfaceloadsⅡ:Computationand numerical results[J].J Geophy Res,68:485--496.
Pollitz F F.1996.Coseismic deformation fromearthquake faultingin a layered spherical Earth[J].Geophys J Int,125:1--4.
Rundle J B.1980.Static elastic-gravitational deformation of a layered half space by point couple sources[J].J GeophysRes,85:5355--5363.
Sun W,Okubo S.2002.Effects of the earth’s spherical curvature and radial heterogeneity in dislocation studies—for apoint dislocation[J].Geophys R L,29(12):461--464.
Tal wandl M.1959.Acrustal section across the Puerto Pico Trench[J].J Geophys Res,64(10):1545--1556.
Wang H.1999.Surface vertical displacements potential,perturabtions and gravity changes of a viscoelastic earth modelinduced by inernal point dislocations[J].Geophys J Int,137(2):429--440.
Wang Rongjiang,Lorenzo-Martin F,Roth F.2006.PSGRN/PSCMP-a newcode for caluclation co-and post-seismic de-formation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Computers andGeosciences,32:527--541.
Wang C Y,Han WB,Wu J P.2007.Crustal stuacture beneachthe easton margin of the Tibetan Plateau andits tectonici mplication[J].J Geophys Res,112(B07307):1--21.
②李辉等.2008.汶川8级地震后震区重力应急观测报告.
陈国光,许凤桔,周荣军,徐杰,周本刚,黎小刚,叶友青.2007.龙门山断裂带晚第四纪活动性分段的初步研究[J].地震地质,29(3):657--673.
陈学波,吴跃强,杜平山,李金森,吴玉荣,蒋国芳,赵静娴.1988.龙门山构造带两侧地壳速度结构特征[G]∥中国大陆深部构造的研究与进展.北京:地震出版社:97--113.
陈运泰,许力生,张勇,杜海林,冯万鹏,刘超,李春来,张红霞.2008.2008年5月12日汶川特大地震震源特性分析报告[EB/OL].[2008-05-26].http:∥www.csi.ac.cn/sichuan/.
崔作舟,陈纪平,吴苓.1996.花石峡—邵阳深部地壳的结构和构造[M].北京:地质出版社:49--168.
邓明莉,孙和平,徐建桥.2008.GPS数据约束的昆仑MS8.1地震断层的分段模型[J].大地测量与地球动力学,28(4):31--37.
李传友,宋方敏,冉勇康.2004.龙门山断裂带北段晚第四纪活动性讨论[J].地震地质,26(2):248--258.
李国和,王思敬,尚彦军,张强.2000.川滇交界地区地壳结构及现代地壳活动模式[J].地质力学学报,6(2):82--91.
申重阳,李辉,谈洪波.2008.汶川8.0级地震同震重力与形变效应模拟[J].大地测量与地球动力学,28(5):6--12.
孙文科.2008.地震火山活动产生重力变化的理论与观测研究的进展及现状[J].大地测量与地球动力学,4:44--53.
谭凯,李杰,王琪.2007.大地测量约束下的阿尔泰岩石圈流变结构[J].地球物理学报,50(6):1713--1718.
谈洪波,申重阳,李辉.2008.断层位错引起的地表重力变化特征研究[J].大地测量与地球动力学,28(4):54--62.
滕吉文,白登海,杨辉,闫雅芬,张洪双,张永谦,阮小敏.2008.2008汶川MS8.0级地震发生的深层过程和动力学响应[J].地球物理学报,51(5):1385--1402.
汪汉胜.1999.黏弹负荷形变理论的应用[D].武汉:中国科学院测量与地球物理研究所:8--9.
王椿镛,韩渭宾,吴建平,楼海,白志明.2003.松潘—甘孜造山带地壳速度结[J].地震学报,25(3):229--241.
吴建平,明跃红,王椿镛.2006.川滇地区速度结构的区域地震波形反演研究[J].地球物理学报,49(5):1369--1376.
邢乐林,李辉,懂正瑶,何志堂,刘少明,谈洪波.2008.成都地震基准台重复绝对重力测量结果分析[J].大地测量与地球动力学,28(6):38--42.
袁旭东.2007.中国三大震例同震形变的研究[D].武汉:中国科学院测量与地球物理研究所:39--41.
赵珠,范军,郑斯华.1997.龙门山断裂带地壳速度结构和震源位置的精确修定[J].地震学报,19(6):615--622.
周荣军,李勇,Alexander L Densmore,Michael A Ellis,何玉林,王凤林,黎小刚.2006.青藏高原东缘活动构造[J].矿物岩石,26(2):40--51.
Alexander L Densmore,Michael A.2007.Active tectonics of the Beichuan and Pengguan faults at the eastern margin ofthe Tibetan Plateau[J].Tectonics,26,TC4005:1-17.
Huang J L.2007.Lithospheric structure and its relationship to seismic and volcanic activity in southwest China[J].JGeophys Res,107(BIO2255):1--14.
Ji Chen,UCSB,Hayes Gavin.2008.NEIC,Preli minary Result of the May12,2008MW7.9Eastern Sichuan,ChinaEarthquake.[2008-05].http:∥earthquake.usgs.gov/eqcenter/eqinthenews/us2008ryan/.
Longman I M.1963.A Green’s functionfor determiningthe deforation of the Earth under surfaceloadsⅡ:Computationand numerical results[J].J Geophy Res,68:485--496.
Pollitz F F.1996.Coseismic deformation fromearthquake faultingin a layered spherical Earth[J].Geophys J Int,125:1--4.
Rundle J B.1980.Static elastic-gravitational deformation of a layered half space by point couple sources[J].J GeophysRes,85:5355--5363.
Sun W,Okubo S.2002.Effects of the earth’s spherical curvature and radial heterogeneity in dislocation studies—for apoint dislocation[J].Geophys R L,29(12):461--464.
Tal wandl M.1959.Acrustal section across the Puerto Pico Trench[J].J Geophys Res,64(10):1545--1556.
Wang H.1999.Surface vertical displacements potential,perturabtions and gravity changes of a viscoelastic earth modelinduced by inernal point dislocations[J].Geophys J Int,137(2):429--440.
Wang Rongjiang,Lorenzo-Martin F,Roth F.2006.PSGRN/PSCMP-a newcode for caluclation co-and post-seismic de-formation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Computers andGeosciences,32:527--541.
Wang C Y,Han WB,Wu J P.2007.Crustal stuacture beneachthe easton margin of the Tibetan Plateau andits tectonici mplication[J].J Geophys Res,112(B07307):1--21.
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