汶川地震擂鼓地区地表变形特征及其机制探讨
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摘要
基于擂鼓附近地表破裂几何形态的特殊性以及对擂鼓地区地震地表破裂机制存在的不同认识,本文通过野外实际调查测量,并结合已有的文献资料对擂鼓地区地震地表变形特征进行了详细研究。分析结果认为:擂鼓附近几何形态的变化、同震位移量的明显偏小,以及破裂带拐弯处的表层物质发散运动,表明该地区具有一般挤压阶区的特征。由于北川—映秀断裂北段是兼有逆冲运动和右旋走滑运动的断裂,所以相比于一般挤压阶区,擂鼓挤压阶区受到了更强烈的挤压隆升,并且仍受到逆冲引起的撕裂断层作用。擂鼓阶区内形成的滑坡、地表破裂以及鼓包都是局部块体受到强烈挤压作用的结果,而撕裂断层作用影响较小,且完全被挤压隆升变形所掩盖。根据文中的研究并结合已有的深部运动资料,笔者构建了擂鼓挤压阶区三维结构模型。对擂鼓地区的同震变形机制研究不仅有利于我们深入地理解汶川地震的地表破裂过程,也可为断裂阶区内的防震减灾提供理论依据。
The special characteristics of the rupture induced by 5.12 Wenchuan earthquake in Leigu area is discussed based on the field materials and reported surveying data in this paper because of its unique geometric features and different mechanisms presented by different researchers.Investigation results suggested that the obviously smaller co-seismic deformation and the moving characters of the superficial matter in Leigu area match the general features of restraining step-over.But the north segment of Beichuan-Yingxiu Fault's thrust offset is almost equal to its dextral offset,so Leigu restraining step-over(LRS) received more compression than other step-over in the pure strike-slip fault,and the rupture,landslide and pressure ridges were mainly induced by the strong compressional action.Furthermore,the step-over was under the action of the tear fault induced by thrust,but the impact was so small that it was covered by the extruded deformation totally.Combining our research with the materials of deep moving by other geophysical researches,a 3D structural model was introduced to explain the role of Leigu restraining step-over during the forming process of rupture.Our research is not only in favor of the understanding of the process of the Wenchuan earthquake,but also provides the theoretical basis for earthquake disaster prevention in step-over.
The special characteristics of the rupture induced by 5.12 Wenchuan earthquake in Leigu area is discussed based on the field materials and reported surveying data in this paper because of its unique geometric features and different mechanisms presented by different researchers.Investigation results suggested that the obviously smaller co-seismic deformation and the moving characters of the superficial matter in Leigu area match the general features of restraining step-over.But the north segment of Beichuan-Yingxiu Fault's thrust offset is almost equal to its dextral offset,so Leigu restraining step-over(LRS) received more compression than other step-over in the pure strike-slip fault,and the rupture,landslide and pressure ridges were mainly induced by the strong compressional action.Furthermore,the step-over was under the action of the tear fault induced by thrust,but the impact was so small that it was covered by the extruded deformation totally.Combining our research with the materials of deep moving by other geophysical researches,a 3D structural model was introduced to explain the role of Leigu restraining step-over during the forming process of rupture.Our research is not only in favor of the understanding of the process of the Wenchuan earthquake,but also provides the theoretical basis for earthquake disaster prevention in step-over.
引文
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[6]Li Y,Zhou R J,Densmore A L,et al.Surface rupture anddeformation of the Yingxiu-Beichuan fault by the Wenchuanearthquake[J].Acta Geologica Sinica,2008,82(12):1688-1706(in Chinese).
[7]Li HB,Fu X F,Woerd J V,et al.Co-seismic surface rup-ture and dextral-slip oblique thrusting of theMs8.0 Wen-chuan earthquake[J].Acta Geologica Sinica,2008,82(12):1623-1643(in Chinese).
[8]Fu B H,Shi P L,Zhang Z W.Spatial characteristics of thesurface rupture produced by theMs8.0 Wenchuan earth-quake using high-resolution remote sensingi magery[J].ActaGeologica Sinica,2008,82(12):1679-1687(in Chinese).
[9]Liu J,Zhang Z H,Wen L,et al.TheMs8.0 Wenchuanearthquake co-seismic rupture and its tectonic i mplications:An out-of-sequence thrusting event with slip partitioned onmultiple faults[J].Acta Geologica Sinica,2008,82(12):1707-1722(in Chinese).
[10]Liu Z J,Zhang Z H,Wen L,et al.Co-seismic ruptures ofthe 12 May 2008,Ms8.0 Wenchuan earthquake,Sichuan:East-west crustal shortening on oblique,parallel thrusts a-long the eastern edge of Tibet[J].EPSL,2009,286:355-370.
[11]Chen G H,Xu X W,Yu G H,et al.Co-seismic slip and slippartitioning of multi-faults during theMs8.0 2008 Wenchuanearthquake[J].Chinese Journal of Geophysics,2009,52(5):1384-1394(in Chinese).
[12]Yu G H,Xu X W,Klinger Y,et al.Fault-scarpfeatures andcascading-rupture model for the Wenchuan earthquake(Mw7.9),Eastern Tibetan Plateau,China[J].BSSA,2010(inpress).
[13]Yan L,Li Y,Densmore A L,et al.Surface rupture of Leigufault in Beichuan area after Wenchuan earthquake,and itssignificance[J].Quaternary Sciences,2009,29(3):535-545(in Chinese).
[14]Li Y,Huang R Q,Densmore A L,et al.Surface rupture ofXiaoyudong fault caused by Wenchuan earthquake andits ge-ological significance[J].Quaternary Sciences,2009,29(3):502-512(in Chinese).
[15]Zhang J L,Shen X H,Xu Y R,et al.Surface rupture fea-tures and segmentation of theMs8.0 Wenchuan earthquake[J].Earthquake,2009,29(1):149-163(in Chinese).
[16]Wei Z Y,He H L,Dong S P,et al.Rupture analysis of theWenchuan earthquake at two observation stations by geome-try and kinematics[J].Seismology and Geology,2008,30(4):1023-1032(in Chinese).
[17]Project Teamof CMONOC.The co-seismic displacement fieldof WenchuanMs8.0 earthquake,measured by GPS[J].Sci-ence in China:Series D,2008,38(10):1195-1206(in Chi-nese).
[18]Wang W M,Zhao L F,Li J,et al.Rupture process of theMs8.0 Wenchuan earthquake of Sichuan,China[J].ChineseJournal of Geophysics,2008,51(5):1403-1410(in Chi-nese).
[19]Wang H,Ran Y K,Chen L C,et al.The investigation ofhorizontal shortening and amount of reverse-faulting fromtrenching across the surface rupture of the 2008Mw7.9 Wen-chuan earthquake,China[J].Tectonophysics,2010,491:10-21(in press).
[20]Sibson R H.Stopping of earthquake ruptures at dilatationalfault jogs[J].Nature,1985,316:248-251.
[21]Duman T Y,Emre O,Dogan A,et al.Step-over and bendstructures along the 1999 Duzce earthquake surface rupture,North Anatolianfault,Turkey[J].Bulletin of the Seismolog-ical Society of America,2005,94(4):1250-1262.
[22]Escalona A,Mann P.Tectonic controls of the right-lateralBurro Negro tear fault on Paleogene structure and stratigra-phy,northeastern Maracaibo basin[J].AAPG Bulletin,2006,90(4):479-504.
[23]Dennis.International Tectonic Dictionary[M].Translated byYan Jiaqi.Beijing:Geological Publishing House,1983:81-82(in Chinese).
[2]徐锡伟,闻学泽,叶建青,等.汶川Ms8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):594-629.
[3]徐锡伟,陈桂华,于贵华,等.5.12汶川地震地表破裂基本参数的再论证及其构造内涵分析[J].地球物理学报,2010(待刊).
[6]李勇,周荣军,Densmore A L,等.映秀—北川断裂的地表破裂与变形特征[J].地质学报,2008,82(12):1688-1706.
[7]李海兵,付小方,Woerd J V,等.汶川地震(Ms8.0)地表破裂及其同震右旋斜向逆冲作用[J].地质学报,2008,82(12):1623-1643.
[8]付碧宏,时丕龙,张志武.四川汶川Ms8.0大地震地表破裂带的遥感影像解译[J].地质学报,2008,82(12):1679-1687.
[9]刘静,张智慧,文力,等.汶川8级大地震同震破裂的特殊性及构造意义:多条平行断裂同时活动的反序型逆冲地震事件[J].地质学报,2008,82(12):1707-1722.
[11]陈桂华,徐锡伟,于贵华,等.2008年汶川Ms8.0地震多断裂破裂的近地表同震滑移及滑移分解[J].地球物理学报,2009,52(5):1384-1394.
[13]闫亮,李勇,Densmore A L,等.北川地区擂鼓断裂在汶川地震中的地表破裂及其意义[J].第四纪研究,2009,29(3):535-545.
[14]李勇,黄润秋,Densmore A L,等.龙门山小鱼洞断裂在汶川地震中的地表破裂及地质意义[J].第四纪研究,2009,29(3):502-512.
[15]张军龙,申旭辉,徐岳仁,等.汶川8级大地震的地表破裂特征及分段[J].地震,2009,29(1):149-163.
[16]魏占玉,何宏林,董绍鹏,等.从两个地表破裂点的几何学与运动学特征分析汶川地震的破裂方式[J].地震地质,2008,30(4):1023-1032.
[17]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.
[18]王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.
[23]Dennis.国际构造地质词典[M].阎嘉祺译.北京:地质出版社,1983:81-82.
[2]Xu X W,Wen X Z,Ye J Q,et al.TheMs8.0 Wenchuanearthquake surface ruptures andits seismogenic structure[J].Seismology and Geology,2008,30(3):594-629(in Chi-nese).
[3]Xu X W,Chen G H,Yu G H,et al.Reevaluation of surfacerupture parameters of the 5.12 Wenchuan earthquake anditstectonic i mplication for Tibetan uplift[J].Chinese Journal ofGeophysics,2010(in press)(in Chinese).
[4]Xu X W,Wen X Z,Yu G H,et al.Co-seismic reverse-andoblique-slip surface faulting generated by the 2008Mw7.9Wenchuan earthquake,China[J].Geology,2009,37(6):515-518.
[5]Xu X,Yu G,Chen G,et al.Parameters of coseismic reverse-and oblique-slip surface ruptures of the 2008 Wenchuan earth-quake,eastern Tibetan Plateau[J].Acta Geologica Sinica,2009,83(4):673-684.
[6]Li Y,Zhou R J,Densmore A L,et al.Surface rupture anddeformation of the Yingxiu-Beichuan fault by the Wenchuanearthquake[J].Acta Geologica Sinica,2008,82(12):1688-1706(in Chinese).
[7]Li HB,Fu X F,Woerd J V,et al.Co-seismic surface rup-ture and dextral-slip oblique thrusting of theMs8.0 Wen-chuan earthquake[J].Acta Geologica Sinica,2008,82(12):1623-1643(in Chinese).
[8]Fu B H,Shi P L,Zhang Z W.Spatial characteristics of thesurface rupture produced by theMs8.0 Wenchuan earth-quake using high-resolution remote sensingi magery[J].ActaGeologica Sinica,2008,82(12):1679-1687(in Chinese).
[9]Liu J,Zhang Z H,Wen L,et al.TheMs8.0 Wenchuanearthquake co-seismic rupture and its tectonic i mplications:An out-of-sequence thrusting event with slip partitioned onmultiple faults[J].Acta Geologica Sinica,2008,82(12):1707-1722(in Chinese).
[10]Liu Z J,Zhang Z H,Wen L,et al.Co-seismic ruptures ofthe 12 May 2008,Ms8.0 Wenchuan earthquake,Sichuan:East-west crustal shortening on oblique,parallel thrusts a-long the eastern edge of Tibet[J].EPSL,2009,286:355-370.
[11]Chen G H,Xu X W,Yu G H,et al.Co-seismic slip and slippartitioning of multi-faults during theMs8.0 2008 Wenchuanearthquake[J].Chinese Journal of Geophysics,2009,52(5):1384-1394(in Chinese).
[12]Yu G H,Xu X W,Klinger Y,et al.Fault-scarpfeatures andcascading-rupture model for the Wenchuan earthquake(Mw7.9),Eastern Tibetan Plateau,China[J].BSSA,2010(inpress).
[13]Yan L,Li Y,Densmore A L,et al.Surface rupture of Leigufault in Beichuan area after Wenchuan earthquake,and itssignificance[J].Quaternary Sciences,2009,29(3):535-545(in Chinese).
[14]Li Y,Huang R Q,Densmore A L,et al.Surface rupture ofXiaoyudong fault caused by Wenchuan earthquake andits ge-ological significance[J].Quaternary Sciences,2009,29(3):502-512(in Chinese).
[15]Zhang J L,Shen X H,Xu Y R,et al.Surface rupture fea-tures and segmentation of theMs8.0 Wenchuan earthquake[J].Earthquake,2009,29(1):149-163(in Chinese).
[16]Wei Z Y,He H L,Dong S P,et al.Rupture analysis of theWenchuan earthquake at two observation stations by geome-try and kinematics[J].Seismology and Geology,2008,30(4):1023-1032(in Chinese).
[17]Project Teamof CMONOC.The co-seismic displacement fieldof WenchuanMs8.0 earthquake,measured by GPS[J].Sci-ence in China:Series D,2008,38(10):1195-1206(in Chi-nese).
[18]Wang W M,Zhao L F,Li J,et al.Rupture process of theMs8.0 Wenchuan earthquake of Sichuan,China[J].ChineseJournal of Geophysics,2008,51(5):1403-1410(in Chi-nese).
[19]Wang H,Ran Y K,Chen L C,et al.The investigation ofhorizontal shortening and amount of reverse-faulting fromtrenching across the surface rupture of the 2008Mw7.9 Wen-chuan earthquake,China[J].Tectonophysics,2010,491:10-21(in press).
[20]Sibson R H.Stopping of earthquake ruptures at dilatationalfault jogs[J].Nature,1985,316:248-251.
[21]Duman T Y,Emre O,Dogan A,et al.Step-over and bendstructures along the 1999 Duzce earthquake surface rupture,North Anatolianfault,Turkey[J].Bulletin of the Seismolog-ical Society of America,2005,94(4):1250-1262.
[22]Escalona A,Mann P.Tectonic controls of the right-lateralBurro Negro tear fault on Paleogene structure and stratigra-phy,northeastern Maracaibo basin[J].AAPG Bulletin,2006,90(4):479-504.
[23]Dennis.International Tectonic Dictionary[M].Translated byYan Jiaqi.Beijing:Geological Publishing House,1983:81-82(in Chinese).
[2]徐锡伟,闻学泽,叶建青,等.汶川Ms8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):594-629.
[3]徐锡伟,陈桂华,于贵华,等.5.12汶川地震地表破裂基本参数的再论证及其构造内涵分析[J].地球物理学报,2010(待刊).
[6]李勇,周荣军,Densmore A L,等.映秀—北川断裂的地表破裂与变形特征[J].地质学报,2008,82(12):1688-1706.
[7]李海兵,付小方,Woerd J V,等.汶川地震(Ms8.0)地表破裂及其同震右旋斜向逆冲作用[J].地质学报,2008,82(12):1623-1643.
[8]付碧宏,时丕龙,张志武.四川汶川Ms8.0大地震地表破裂带的遥感影像解译[J].地质学报,2008,82(12):1679-1687.
[9]刘静,张智慧,文力,等.汶川8级大地震同震破裂的特殊性及构造意义:多条平行断裂同时活动的反序型逆冲地震事件[J].地质学报,2008,82(12):1707-1722.
[11]陈桂华,徐锡伟,于贵华,等.2008年汶川Ms8.0地震多断裂破裂的近地表同震滑移及滑移分解[J].地球物理学报,2009,52(5):1384-1394.
[13]闫亮,李勇,Densmore A L,等.北川地区擂鼓断裂在汶川地震中的地表破裂及其意义[J].第四纪研究,2009,29(3):535-545.
[14]李勇,黄润秋,Densmore A L,等.龙门山小鱼洞断裂在汶川地震中的地表破裂及地质意义[J].第四纪研究,2009,29(3):502-512.
[15]张军龙,申旭辉,徐岳仁,等.汶川8级大地震的地表破裂特征及分段[J].地震,2009,29(1):149-163.
[16]魏占玉,何宏林,董绍鹏,等.从两个地表破裂点的几何学与运动学特征分析汶川地震的破裂方式[J].地震地质,2008,30(4):1023-1032.
[17]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.
[18]王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.
[23]Dennis.国际构造地质词典[M].阎嘉祺译.北京:地质出版社,1983:81-82.
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