四川芦山7.0地震和汶川8.0地震震源区地壳岩石圈变形特征分析
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摘要
地壳和岩石圈变形特征研究对于深入了解中强地震的深部孕震环境具有重要科学意义.本文联合P和S波远震接收函数偏移成像结果,对发生过芦山7.0地震和汶川8.0地震的龙门山断裂带及附近区域地壳和岩石圈结构进行分析.结果揭示出在青藏高原向四川盆地过渡的龙门山断裂带,Moho面和岩石圈底界面(LAB)呈现出强烈变形,特别是芦山地震和汶川地震震源区下方地壳出现了错断、下凹,岩石圈也呈现下凹变形特征.这种地壳及岩石圈变形所代表的高应力的积累可能是汶川和芦山地震发生的重要深部地球动力学背景.
Study of the crustal and lithospheric deformation is important to understanding of the deep environment of moderate and major earthquakes. In this work, the P and S receiver functions from the Sichuan seismic network are jointly used to study the crustal and lithospheric structures beneath the Lushan 7.0 earthquake on 20 April 2013 and Wenchuan 8.0 earthquake on 12 May 2008. The results indicate that there is strong deformation of the Moho and LAB (lithosphere-asthenosphere boundary) beneath the transition region from the Tibetan plateau to the Sichuan basin. The offset and downward warping of the Moho are observed beneath the Lushan and Wenchuan earthquakes with the sinking LAB. Such intense deformation may imply the accumulation of high stresses, which is probably the important geodynamic context of the Lushan and Wenchuan earthquakes.
Study of the crustal and lithospheric deformation is important to understanding of the deep environment of moderate and major earthquakes. In this work, the P and S receiver functions from the Sichuan seismic network are jointly used to study the crustal and lithospheric structures beneath the Lushan 7.0 earthquake on 20 April 2013 and Wenchuan 8.0 earthquake on 12 May 2008. The results indicate that there is strong deformation of the Moho and LAB (lithosphere-asthenosphere boundary) beneath the transition region from the Tibetan plateau to the Sichuan basin. The offset and downward warping of the Moho are observed beneath the Lushan and Wenchuan earthquakes with the sinking LAB. Such intense deformation may imply the accumulation of high stresses, which is probably the important geodynamic context of the Lushan and Wenchuan earthquakes.
引文
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[13]刘启元,李昱,陈九辉等.汶川MS8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009,52(2):309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan MS8.0earthquake:preliminary study of the S-wave velocitystructure of the crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
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[15]楼海,王椿镛,吕智勇等.2008年汶川Ms8.0级地震的深部构造环境——远震P波接收函数和布格重力异常的联合解释.中国科学D辑:地球科学,2008,38(10):1207-1220.Lou H,Wang C Y,LüZ Y,et al.Deep tectonic setting ofthe 2008 Wenchuan Ms8.0 earthquake in southwesternChina-Joint analysis of teleseismic P-wave receiver functionsand Bouguer gravity anomalies.Science in China Series D-Earth Sciences,2009,52(2)166-179,doi:10.1007/s11430-009-0009-z.
[16]王椿镛,楼海,吕智勇等.青藏高原东部地壳上地幔S波速度结构:下地壳流的深部环境.中国科学D辑:地球科学,2008,38(1):22-32.Wang C Y,Lou H,LüZ Y,et al.S-wave crustal and uppermantle′s velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow.Science in ChinaSeries D-Earth Sciences,2008,51(2):263-274,doi:10.1007/s11430-008-0008-5.
[17]沈旭章,梅秀苹,杨辉.汶川地震破裂带地壳速度结构研究.地球物理学进展,2011,26(2):477-488,doi:10.3969/j.issn.1004-2903.2011.02.012.Shen X Z,Mei X P,Yang H.Study on the crustal structuresbeneath Wenchuan earthquake rupture zone.Progress inGeophysics(in Chinese),2011,26(2):477-488,doi:10.3969/j.issn.1004-2903.2011.02.012.
[18]Zhang Z J,Wang Y H,Chen Y,et al.Crustal structureacross Longmenshan fault belt from passive source seismicprofiling.Geophysical Research Letter,2009,36(17):L17310.
[19]Pan S Z,Niu F L.Large contrasts in crustal structure andcomposition between the Ordos plateau and the NE Tibetanplateau from receiver function analysis.Earth Planet.Sci.Lett.,2011,303(3-4):291-298.
[20]Zhang Z J,Yuan X H,Chen Y,et al.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letters,2010,292(3-4):254-264.
[21]Zhang Z J,Deng Y F,Teng J W,et al.An overview of thecrustal structure of the Tibetan plateau after 35years of deepseismic soundings.Journal of Asia Earth Sciences,2011,40(4):977-989.
[22]Zhang Z J,Klemperer S,Bai Z M,et al.Crustal structure ofthe Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,2011,19(4):994-100.
[23]Hu J F,Yang H Y,Xu X Q,et al.Lithospheric structureand crust-mantle decoupling in the southeast edge of theTibetan Plateau.Gondwana Research,2012,22(3-4):1060-1067,doi:./10.1016/j.gr.2012.01.003.
[24]Chen Y,Zhang Z J,Sun C Q,et al.Crustal anisotropy fromMoho converted Ps wave splitting analysis and geodynamicimplications beneath the eastern margin of Tibet andsurrounding regions.Gondwana Research,2012,doi:10.1016/j.gr.2012.04.003.
[25]Shen X Z,Mei X P,Zhang Y S.The crustal and upper-mantle structures beneath the northeastern margin of Tibet.Bull.Seismol.Soc.Am.,2011,101(6):2782-2795,doi:10.1785/0120100112.
[26]Tian X,Wu Q,Zhang Z,et al.Joint imaging by teleseismicconverted and multiple waves and its applicaton in theINDEPTH—III passive seismic array.Geophys.Res.Lett.,2005,32:L21315,doi:10.1029/2005GL023686.
[27]Tian X B,Zhao D P,Zhang H S,et al.Mantle transitionzone topography and structure beneath the central Tien Shanorogenic belt.J.Geophys.Res.,2010,115(B10):B10308,doi:10.1029/2008JB006229.
[28]Tian X B,Teng J W,Zhang H S,et al.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Physics ofthe Earth and Planetary Interiors,2011,184(3-4):186-193,doi:10.1016/j.pepi.2010.11.007.
[29]Wittlinger G,Farra V.Converted waves reveal a thick andlayered tectosphere beneath the Kalahari super-craton.EarthPlanet.Sci.Lett.,2007,254(3-4):404-415.
[30]Yuan X H,Ni J,Kind R,et al.Lithospheric and uppermantle structure of southern Tibet from a seismologicalpassive source experiment.J.Geophys.Res.,1997,102(B12):27491-27500.
[31]柳畅,朱伯靖,石耀霖.粘弹性数值模拟龙门山断裂带应力积累及大震复发周期.地质学报,2012,86(1):157-169.Liu C,Zhu B J,Shi Y L.Stress accumulation of theLongmenshan fault and recurrence interval of Wenchuanearthquake based on viscoelasticity simulation.ActaGeologica Sinica(in Chinese),2012,86(1):157-169.
[32]郑秀芬,欧阳飚,张东宁等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52(5):1412-1417,doi:10.3969/j.issn.0001-5733.2009.05.031.Zheng X F,Ouyang B,Zhang D N,et al.Technical systemconstruction of Data Backup Centre for China SeismographNetwork and the data support to researches on the Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2009,52(5):1412-1417,doi:10.3969/j.issn.0001-5733.2009.05.031.
[33]Wessel P,Smith W H F.New version of the generic mappingtools.Eos Trans.Am.Geophys.Union.,1995,76(33):329.
10.6038/cjg20130434.Liu J,Yi G X,Zhang Z W,et al.Introduction to theLushan,Sichuan M7.0earthquake on 20April 2013.ChineseJ.Geophys.(in Chinese),2013,56(4):1404-1407,doi:
10.6038/cjg20130434.
[2]张勇,许力生,陈运泰.芦山4.20地震破裂过程及其致灾特征初步分析.地球物理学报,2013,56(4):1408-1411,doi:10.6038/cjg20130435.Zhang Y,Xu L S,Chen Y T.Rupture process of the Lushan4.20earthquake and preliminary analysis on the disaster-causing mechanism.Chinese J.Geophys.(in Chinese),2013,56(4):1408-1411,doi:10.6038/cjg20130435.
[3]王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震震源破裂过程反演初步结果.地球物理学报,2013,56(4):1412-1417,doi:10.6038/cjg20130436.Wang W M,Hao J L,Yao Z X.Preliminary result forrupture process of Apr.20,2013,Lushan Earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2013,56(4):1412-1417,doi:10.6038/cjg20130436.
[4]曾祥方,罗艳,韩立波等.2013年4月20日四川芦山MS7.0地震:一个高角度逆冲地震.地球物理学报,2013,56(4):1418-1424,doi:10.6038/cjg20130437.Zeng X F,Luo Y,Han L B,et al.The Lushan MS7.0earthquake on 20 April 2013:A high-angle thrust event.Chinese J.Geophys.(in Chinese),2013,56(4):1418-1424,doi:10.6038/cjg20130437.
[5]张培震,徐锡伟,闻学泽等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4):1066-1073.Zhang P Z,Xu X W,Wen X Z,et al.Slip rates andrecurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May 12Wenchuan earthquake,2008,Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(4):1066-1073.
[6]Royden L H,Burchfiel B C,King R W,et al.Surfacedeformation and lower crustal flow in eastern Tibet.Science,1997,276(5313):788-790.doi:10.1029/2002TC001402.
[7]Clark M K,Royden L H.Topographic ooze:building theeastern margin of Tibet by lower crustal flow.Geology,2000,28(8):703-706.doi:10.1130/0091-7613.
[8]石玉涛,高原,张永久等.松潘—甘孜地块东部、川滇地块北部与四川盆地西部的地壳剪切波分裂.地球物理学报,2013,56(2):481-494.doi:10.6038/cjg20130212.Shi Y T,Gao Y,Zhang Y J,et a1.Shear-wave splitting inthe crust in Eastern Songpan-Garzêblock,Sichuan-Yunnanblock and Western Sichuan Basin.Chinese J.Geophys.(inChinese),2013,56(2):481-494,doi:10.6038/cjg20130212.
[9]高原,王琼,赵博涛等.龙门山断裂带中南段的一个破裂空段—芦山地震的震后效应.中国科学(D辑:地球科学),2013,43(6):1038-1046.Gao Y,Wang Q,Zhao B T,et al.A rupture blank zone inmiddle south part of Longmenshan Faults:Effect afterLushan MS7.0 earthquake of 20 April 2013in Sichuan,China.Science China:Earth Sciences,2013,doi:10.1007/s11430-013-4646-x.
[10]Wang C Y,Han W B,Wu J P,et al.Crustal structurebeneath the eastern margin of the Tibetan Plateau and itstectonic implications.J.Geophys.Res.,2007,112(B7):B07307,doi:10.1029/2005JB003873.
[11]Xu L L,Rondenay S,van der Hilst R D.Structure of thecrust beneath the southeastern Tibetan Plateau fromteleseismic receiver functions.Phys.Earth Planet.Inter.,2007,165(3-4):176-193.
[12]Burchfiel B C,Royden L H,van der Hilst R D,et al.Ageological and geophysical context for the Wenchuanearthquake of 12 May 2008,Sichuan,People′s Republic ofChina.GSA Today,2008,18(7):4-11,doi:10.1130/GSATG18A.1.
[13]刘启元,李昱,陈九辉等.汶川MS8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009,52(2):309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan MS8.0earthquake:preliminary study of the S-wave velocitystructure of the crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
[14]雷建设,赵大鹏,苏金蓉等.龙门山断裂带地壳精细结构与汶川地震发震机理.地球物理学报,2009,52(2):339-345.Lei J S,Zhao D P,Su J R,et al.Fine seismic structureunder the Longmenshan fault zone and the mechanism of thelarge Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):339-345.
[15]楼海,王椿镛,吕智勇等.2008年汶川Ms8.0级地震的深部构造环境——远震P波接收函数和布格重力异常的联合解释.中国科学D辑:地球科学,2008,38(10):1207-1220.Lou H,Wang C Y,LüZ Y,et al.Deep tectonic setting ofthe 2008 Wenchuan Ms8.0 earthquake in southwesternChina-Joint analysis of teleseismic P-wave receiver functionsand Bouguer gravity anomalies.Science in China Series D-Earth Sciences,2009,52(2)166-179,doi:10.1007/s11430-009-0009-z.
[16]王椿镛,楼海,吕智勇等.青藏高原东部地壳上地幔S波速度结构:下地壳流的深部环境.中国科学D辑:地球科学,2008,38(1):22-32.Wang C Y,Lou H,LüZ Y,et al.S-wave crustal and uppermantle′s velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow.Science in ChinaSeries D-Earth Sciences,2008,51(2):263-274,doi:10.1007/s11430-008-0008-5.
[17]沈旭章,梅秀苹,杨辉.汶川地震破裂带地壳速度结构研究.地球物理学进展,2011,26(2):477-488,doi:10.3969/j.issn.1004-2903.2011.02.012.Shen X Z,Mei X P,Yang H.Study on the crustal structuresbeneath Wenchuan earthquake rupture zone.Progress inGeophysics(in Chinese),2011,26(2):477-488,doi:10.3969/j.issn.1004-2903.2011.02.012.
[18]Zhang Z J,Wang Y H,Chen Y,et al.Crustal structureacross Longmenshan fault belt from passive source seismicprofiling.Geophysical Research Letter,2009,36(17):L17310.
[19]Pan S Z,Niu F L.Large contrasts in crustal structure andcomposition between the Ordos plateau and the NE Tibetanplateau from receiver function analysis.Earth Planet.Sci.Lett.,2011,303(3-4):291-298.
[20]Zhang Z J,Yuan X H,Chen Y,et al.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letters,2010,292(3-4):254-264.
[21]Zhang Z J,Deng Y F,Teng J W,et al.An overview of thecrustal structure of the Tibetan plateau after 35years of deepseismic soundings.Journal of Asia Earth Sciences,2011,40(4):977-989.
[22]Zhang Z J,Klemperer S,Bai Z M,et al.Crustal structure ofthe Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,2011,19(4):994-100.
[23]Hu J F,Yang H Y,Xu X Q,et al.Lithospheric structureand crust-mantle decoupling in the southeast edge of theTibetan Plateau.Gondwana Research,2012,22(3-4):1060-1067,doi:./10.1016/j.gr.2012.01.003.
[24]Chen Y,Zhang Z J,Sun C Q,et al.Crustal anisotropy fromMoho converted Ps wave splitting analysis and geodynamicimplications beneath the eastern margin of Tibet andsurrounding regions.Gondwana Research,2012,doi:10.1016/j.gr.2012.04.003.
[25]Shen X Z,Mei X P,Zhang Y S.The crustal and upper-mantle structures beneath the northeastern margin of Tibet.Bull.Seismol.Soc.Am.,2011,101(6):2782-2795,doi:10.1785/0120100112.
[26]Tian X,Wu Q,Zhang Z,et al.Joint imaging by teleseismicconverted and multiple waves and its applicaton in theINDEPTH—III passive seismic array.Geophys.Res.Lett.,2005,32:L21315,doi:10.1029/2005GL023686.
[27]Tian X B,Zhao D P,Zhang H S,et al.Mantle transitionzone topography and structure beneath the central Tien Shanorogenic belt.J.Geophys.Res.,2010,115(B10):B10308,doi:10.1029/2008JB006229.
[28]Tian X B,Teng J W,Zhang H S,et al.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Physics ofthe Earth and Planetary Interiors,2011,184(3-4):186-193,doi:10.1016/j.pepi.2010.11.007.
[29]Wittlinger G,Farra V.Converted waves reveal a thick andlayered tectosphere beneath the Kalahari super-craton.EarthPlanet.Sci.Lett.,2007,254(3-4):404-415.
[30]Yuan X H,Ni J,Kind R,et al.Lithospheric and uppermantle structure of southern Tibet from a seismologicalpassive source experiment.J.Geophys.Res.,1997,102(B12):27491-27500.
[31]柳畅,朱伯靖,石耀霖.粘弹性数值模拟龙门山断裂带应力积累及大震复发周期.地质学报,2012,86(1):157-169.Liu C,Zhu B J,Shi Y L.Stress accumulation of theLongmenshan fault and recurrence interval of Wenchuanearthquake based on viscoelasticity simulation.ActaGeologica Sinica(in Chinese),2012,86(1):157-169.
[32]郑秀芬,欧阳飚,张东宁等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52(5):1412-1417,doi:10.3969/j.issn.0001-5733.2009.05.031.Zheng X F,Ouyang B,Zhang D N,et al.Technical systemconstruction of Data Backup Centre for China SeismographNetwork and the data support to researches on the Wenchuanearthquake.Chinese J.Geophys.(in Chinese),2009,52(5):1412-1417,doi:10.3969/j.issn.0001-5733.2009.05.031.
[33]Wessel P,Smith W H F.New version of the generic mappingtools.Eos Trans.Am.Geophys.Union.,1995,76(33):329.
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