四川及邻区地壳流与动力特征研究
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摘要
利用四川地震台网区域地震台站和布设于该地区的流动地震台站的宽频带地震资料,采用接收函数反演等方法,对四川及邻区地壳流动与动力作用特征进行研究。结果表明,四川盆地地壳及上地幔速度显著高于青藏高原东缘。盆地中地壳vS值达3.6~3.8km/s,上地幔vS值为4.5~4.8 km/s,且地壳内无低速层,岩性上显示为刚强的地块。青藏高原东缘各台站的vS断面最显著的特征是速度值很小,中地壳vS平均值为3.0~3.4 km/s,上地幔vS值为4.0~4.5km/s。地壳内普遍存在低速层,大部份低速层位于深度20~40km的中地壳,在深度为10~20km的上地壳及40~60km的下地壳中,也出现少量的低速层。受印度板块向北推移的影响,青藏高原东缘在向东运动的过程中受到坚硬的四川盆地的阻挡,产生向南及南东运动。这些运动过程的产生是由于研究区受到较为复杂的力的作用。正是在这些力的作用下,青藏高原东缘成为地质构造复杂、地震活动强烈的地区。低速的地壳流受到刚强的四川盆地的阻挡出现拆层现象,并拆分为向上及向下的2或3支分流。向上的分流侵入上地壳引起地表隆升,形成陡峭的高峰。向下的分流侵入下地壳以至上地幔,使地壳加厚莫霍界面下沉。青藏高原东缘地壳流主要沿活动断裂带上分布。它从青藏高原东缘中部羌塘地块流出,主流沿北西南东的鲜水河断裂带流动,然后转向南北沿安宁河及小江断裂向南。在研究区域的北部,还有1支北东向及东西向到龙门山的地壳流。
On the basis of the broadband data of regional seismic stations from the Sichuan Seismic Network and the mobile seismic stations,the receiver function inversion method was adopted for studying the characteristics of crustal flow and dynamic effects in Sichuan and its adjacent area. The results showed that the crust and upper mantle velocity in the Sichuan basin is significantly higher than the eastern edge of the Qinghai-Tibetan plateau. The earth 's crust velocity vSis from 3. 6 to 3. 8km / s,and the upper mantle velocity vSis from 4. 0 to 4. 5km / s.And there is no low-velocity layer in the crust. The lithology showed a nature of strong block. In the eastern edge of Qinghai-Tibetan plateau,the velocity vSis in low speed,the average velocity vsin earth's crust is from 3. 0 to 3. 4km / s,and the upper mantle velocity vSfrom 4. 0 to 4. 5km /s. Low-velocity layer appear frequently in the crust. Most of the low-velocity layers are located in the intermediate crust with the depth of 20 km to 40 km. A small number of low-velocity layers appear in the upper crust of 10 km ~ 20 km and lower crust of 40 km ~ 60 km. Affected by the Indian Plate northward,the eastern margin of the Qinghai-Tibetan plateau moved in the eastward direction. It was blocked in hard Sichuan Basin. The movement is in the southeastward and southward direction. The movement process is produced by the complicated force in the research area. Because of this,the eastern margin of the Qinghai-Tibetan plateau become complicated geological structure and intense seismic activity area. Low speed crustal flow by strong Sichuan Basin barrier is delaminated into two or three shunts upward and downward. The shunts into upper crust uplift the surface,forming steep peaks. The downward flow intrudes into lower crust and the upper mantle. It makes the crust thickened and Moho sinking. Crust flow is mainly distributed along the active faults of the eastern margin of the Qinghai-Tibetan plateau. In the eastern margin,mainstream flow is from central Qiangtang block,and along the NW-SE direction along the Xianshuihe fault,then turned south and has two branches: a southward branch along the Anninghe fault and Xianshuihe fault,the other along the Nujiang River fault,Lancangjiang River fault zone to the south. In the research area in the north,there is a NE and EW crustal flow to the Longmenshan Mountain fault.
On the basis of the broadband data of regional seismic stations from the Sichuan Seismic Network and the mobile seismic stations,the receiver function inversion method was adopted for studying the characteristics of crustal flow and dynamic effects in Sichuan and its adjacent area. The results showed that the crust and upper mantle velocity in the Sichuan basin is significantly higher than the eastern edge of the Qinghai-Tibetan plateau. The earth 's crust velocity vSis from 3. 6 to 3. 8km / s,and the upper mantle velocity vSis from 4. 0 to 4. 5km / s.And there is no low-velocity layer in the crust. The lithology showed a nature of strong block. In the eastern edge of Qinghai-Tibetan plateau,the velocity vSis in low speed,the average velocity vsin earth's crust is from 3. 0 to 3. 4km / s,and the upper mantle velocity vSfrom 4. 0 to 4. 5km /s. Low-velocity layer appear frequently in the crust. Most of the low-velocity layers are located in the intermediate crust with the depth of 20 km to 40 km. A small number of low-velocity layers appear in the upper crust of 10 km ~ 20 km and lower crust of 40 km ~ 60 km. Affected by the Indian Plate northward,the eastern margin of the Qinghai-Tibetan plateau moved in the eastward direction. It was blocked in hard Sichuan Basin. The movement is in the southeastward and southward direction. The movement process is produced by the complicated force in the research area. Because of this,the eastern margin of the Qinghai-Tibetan plateau become complicated geological structure and intense seismic activity area. Low speed crustal flow by strong Sichuan Basin barrier is delaminated into two or three shunts upward and downward. The shunts into upper crust uplift the surface,forming steep peaks. The downward flow intrudes into lower crust and the upper mantle. It makes the crust thickened and Moho sinking. Crust flow is mainly distributed along the active faults of the eastern margin of the Qinghai-Tibetan plateau. In the eastern margin,mainstream flow is from central Qiangtang block,and along the NW-SE direction along the Xianshuihe fault,then turned south and has two branches: a southward branch along the Anninghe fault and Xianshuihe fault,the other along the Nujiang River fault,Lancangjiang River fault zone to the south. In the research area in the north,there is a NE and EW crustal flow to the Longmenshan Mountain fault.
引文
蔡学林、曹家敏、朱介寿等,2008,龙门山岩石圈地壳三维结构及汶川大地震成因浅析,成都理工大学学报(自然科学版),35(4),357~365。
曹颖、吴小平、沈娅宏等,2013,由震源机制解资料研究川滇地区构造应力场,地震研究,36(2),165~172。
崔作舟、卢德源,陈纪平等,1996,花石峡-邵阳深部地壳结构和构造,49~168,北京:地质出版社。
嘉世旭、张先康、赵金仁等,2009,若尔盖盆地及周缘褶皱造山带地壳结构———深地震测深结,中国科学:D辑,39(9),1200~1208。
刘启元、Rainer Kind、李顺,1996,接收函数复谱比的最大或然性估计及非线性反演,地球物理学报,39(4),502~511。
马杏垣,1989,中国岩石圈动力学图集,1~68,北京:中国地图出版社。
钱晓东、秦嘉政、刘丽芳,2011,云南地区现代构造应力场研究,地震地质,33(2),91~106。
王椿镛、吴建平、楼海等,2003,川西藏东地区的地壳P波速度结构,中国科学:D辑,33(增刊),181~189。
王庆良、崔笃信、王文萍等,2008,川西地区现今垂直地壳运动研究,中国科学:D辑,38(5),598~610。
王阎昭、王恩宁、沈正康,2008,基于GPS资料约束反演川滇地区主要断裂现今活动速率,中国科学:D辑,38(5),582~597。
张培震,2008,青藏高原东缘川西地区的现今构造变形、应变分配与深部动力过程,中国科学:D辑,38(9),1041~1056。
赵国泽、陈小斌、王立凤等,2008,青藏高原东边缘地壳“管流”层的电磁探测证据,科学通报,53(3),345~350。
郑度、姚檀栋,2004,青藏高原隆升与环境效应,北京:科学出版社。
朱介寿,2008,汶川地震的岩石圈深部结构与动力学背景,成都理工大学学报(自然科学版),35(4),348~356。
Bai D,Unsworth M J,Meju M A,et al,2010,Crustal deformation of the eastern Tibetan Plateau revealed by magnetotelluricimaging,Nat Geosci,3,358~362,doi:10.1038/ngeo830.
Burchfiel B C,Chen Z,Liu Y,et al,1995,Tectonics of the Longmen Shan and adjacent regions,Central China,InternationalGeology Reviews,37,661~735.
Burchfiel B C,Royden L H,Van der Hilst R D,et al,2008,A geological and geophysical context for the Wenchuan earthquakeof 12 May 2008,Sichuan,the People’s Republic of China,GSA Today,18,4~11,doi:10.1130/GSATG18A.1.
Clark M K,Royden L H,2000,Topographic ooze:building the Eastern margin of Tibet by lower crustal flow,Geology,28(8),703~706.
Clark M,Royden L,Burchfiel B C,et al,2003,Late Cenozoic uplift of southeastern Tibet:implication for lower crustal flow,Geophys Res Abs,5,12969.
Clark M K,Schoenbohm L M,Royden L H,et al,2004,Surface uplift,tectonics,and erosion of eastern Tibet from large-scaledrainage patterns,Tectonics,23,TC1006,doi:10.1029/2002TC001402.
Clark M K,Bush J W M,Royden L H,2005,Dynamic topography produced by lower crustal flow against reheological strengthheterogeneities bordering the Tibetan Plateau,Geophys J Int,162,575~590,doi:10.1111/j.1365-246X.2005.02580.x.
Gan W,Zhang P,Shen Z K,et al,2007,Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements,J Geophys Res,112,B08416,doi:10.1029/2005 JB004120.
Huang Z W,Su Y,Peng Y,et al,2003,Rayleigh wave tomography of china and adjacent regions,J Geophys Res,108(B2),2073,doi:10.1029/2001JB001696.
Kirby E,Reiners P W,Krol M A,et al,2002,Late Cenozoic evolution of the eastern margin of the Tibetan Plateau:Inferencesfrom 40Ar/39Ar and(U-Th)/He thermochronology,Tectonics,21(1),10.1029/2000TC001246.
Kirby E,Whipple K X,Tang W,et al,2003,Distribution of active rock uplift along the eastern margin of the Tibetan Plateau:Inferences from bedrock channel longitudinal profiles,J Geophys Res,108(B4),2217,doi:10.1029/2001JB000861.
Langston C A,1977,The effect of planar dipping structure on source and receiver responses for constant ray parameter,BullSeism Soc Am,67(4),1029~1050.
Owans T J,Zandt G,Taylor S R,1984,Seismic evidence for ancient rift beneath the Cumberland plateau,Tennessee:A detailedanalysis of broadband teleseismic P waveforms,J Geophys Res,89(B9),7783~7795.
Richardson N J,Densmore A L,Seward D,et al,2008,Extraordinary denudation in the Sichuan Basin:Insights from lowtemperature thermochronology adjacent to the eastern margin of the Tibetan Plateau,J Geophys Res,113,B04409,doi:10.1029/2006JB004739.
Royden L H,Burchfiel B C,King W R,et al,1997,Surface deformation and lower crustal flow in eastern Tibet,Science,276,788~790,doi:10.1126/Science.276.5313.788.
Scchoenbohm I M,Burchfiel B C,Chen Z,2006,Propagation of surface uplift,lower crustal flow and Cenozoic tectonics of thesoutheast margin of the Tibetan plateau,Geology,34(10),813~816.
Shen Z K,Lu J,Wang M,2005,Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau,JGeophys Res,110,B11409,doi:10.1029/2004JB003421.
Vinnik L P,1977,Detection of waves converted from P to SV in the mantle,Phys Earth Planet Int,15,39~45.
Wang Z,Zhao D,Wang J,2010,Deep structure and seismogenesis of the north-south seismic zone in southwest China,J GeophysRes,115,B12334,doi:10.1029/2010JB007797.
Westaway R,1995,Crustal volume balance during the India-Eurasia collision and altitude of the Tibetan plateau:A workinghypothesis,J Geophys Res,100,B8,15173~15192.
曹颖、吴小平、沈娅宏等,2013,由震源机制解资料研究川滇地区构造应力场,地震研究,36(2),165~172。
崔作舟、卢德源,陈纪平等,1996,花石峡-邵阳深部地壳结构和构造,49~168,北京:地质出版社。
嘉世旭、张先康、赵金仁等,2009,若尔盖盆地及周缘褶皱造山带地壳结构———深地震测深结,中国科学:D辑,39(9),1200~1208。
刘启元、Rainer Kind、李顺,1996,接收函数复谱比的最大或然性估计及非线性反演,地球物理学报,39(4),502~511。
马杏垣,1989,中国岩石圈动力学图集,1~68,北京:中国地图出版社。
钱晓东、秦嘉政、刘丽芳,2011,云南地区现代构造应力场研究,地震地质,33(2),91~106。
王椿镛、吴建平、楼海等,2003,川西藏东地区的地壳P波速度结构,中国科学:D辑,33(增刊),181~189。
王庆良、崔笃信、王文萍等,2008,川西地区现今垂直地壳运动研究,中国科学:D辑,38(5),598~610。
王阎昭、王恩宁、沈正康,2008,基于GPS资料约束反演川滇地区主要断裂现今活动速率,中国科学:D辑,38(5),582~597。
张培震,2008,青藏高原东缘川西地区的现今构造变形、应变分配与深部动力过程,中国科学:D辑,38(9),1041~1056。
赵国泽、陈小斌、王立凤等,2008,青藏高原东边缘地壳“管流”层的电磁探测证据,科学通报,53(3),345~350。
郑度、姚檀栋,2004,青藏高原隆升与环境效应,北京:科学出版社。
朱介寿,2008,汶川地震的岩石圈深部结构与动力学背景,成都理工大学学报(自然科学版),35(4),348~356。
Bai D,Unsworth M J,Meju M A,et al,2010,Crustal deformation of the eastern Tibetan Plateau revealed by magnetotelluricimaging,Nat Geosci,3,358~362,doi:10.1038/ngeo830.
Burchfiel B C,Chen Z,Liu Y,et al,1995,Tectonics of the Longmen Shan and adjacent regions,Central China,InternationalGeology Reviews,37,661~735.
Burchfiel B C,Royden L H,Van der Hilst R D,et al,2008,A geological and geophysical context for the Wenchuan earthquakeof 12 May 2008,Sichuan,the People’s Republic of China,GSA Today,18,4~11,doi:10.1130/GSATG18A.1.
Clark M K,Royden L H,2000,Topographic ooze:building the Eastern margin of Tibet by lower crustal flow,Geology,28(8),703~706.
Clark M,Royden L,Burchfiel B C,et al,2003,Late Cenozoic uplift of southeastern Tibet:implication for lower crustal flow,Geophys Res Abs,5,12969.
Clark M K,Schoenbohm L M,Royden L H,et al,2004,Surface uplift,tectonics,and erosion of eastern Tibet from large-scaledrainage patterns,Tectonics,23,TC1006,doi:10.1029/2002TC001402.
Clark M K,Bush J W M,Royden L H,2005,Dynamic topography produced by lower crustal flow against reheological strengthheterogeneities bordering the Tibetan Plateau,Geophys J Int,162,575~590,doi:10.1111/j.1365-246X.2005.02580.x.
Gan W,Zhang P,Shen Z K,et al,2007,Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements,J Geophys Res,112,B08416,doi:10.1029/2005 JB004120.
Huang Z W,Su Y,Peng Y,et al,2003,Rayleigh wave tomography of china and adjacent regions,J Geophys Res,108(B2),2073,doi:10.1029/2001JB001696.
Kirby E,Reiners P W,Krol M A,et al,2002,Late Cenozoic evolution of the eastern margin of the Tibetan Plateau:Inferencesfrom 40Ar/39Ar and(U-Th)/He thermochronology,Tectonics,21(1),10.1029/2000TC001246.
Kirby E,Whipple K X,Tang W,et al,2003,Distribution of active rock uplift along the eastern margin of the Tibetan Plateau:Inferences from bedrock channel longitudinal profiles,J Geophys Res,108(B4),2217,doi:10.1029/2001JB000861.
Langston C A,1977,The effect of planar dipping structure on source and receiver responses for constant ray parameter,BullSeism Soc Am,67(4),1029~1050.
Owans T J,Zandt G,Taylor S R,1984,Seismic evidence for ancient rift beneath the Cumberland plateau,Tennessee:A detailedanalysis of broadband teleseismic P waveforms,J Geophys Res,89(B9),7783~7795.
Richardson N J,Densmore A L,Seward D,et al,2008,Extraordinary denudation in the Sichuan Basin:Insights from lowtemperature thermochronology adjacent to the eastern margin of the Tibetan Plateau,J Geophys Res,113,B04409,doi:10.1029/2006JB004739.
Royden L H,Burchfiel B C,King W R,et al,1997,Surface deformation and lower crustal flow in eastern Tibet,Science,276,788~790,doi:10.1126/Science.276.5313.788.
Scchoenbohm I M,Burchfiel B C,Chen Z,2006,Propagation of surface uplift,lower crustal flow and Cenozoic tectonics of thesoutheast margin of the Tibetan plateau,Geology,34(10),813~816.
Shen Z K,Lu J,Wang M,2005,Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau,JGeophys Res,110,B11409,doi:10.1029/2004JB003421.
Vinnik L P,1977,Detection of waves converted from P to SV in the mantle,Phys Earth Planet Int,15,39~45.
Wang Z,Zhao D,Wang J,2010,Deep structure and seismogenesis of the north-south seismic zone in southwest China,J GeophysRes,115,B12334,doi:10.1029/2010JB007797.
Westaway R,1995,Crustal volume balance during the India-Eurasia collision and altitude of the Tibetan plateau:A workinghypothesis,J Geophys Res,100,B8,15173~15192.
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