斜向逆冲断层相关褶皱的正演模型与实例分析
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摘要
斜向逆冲作用在自然界普遍存在,研究斜向逆冲断层相关褶皱的构造几何学特征,识别断层相关褶皱是否存在斜向逆冲有重要意义。文章采用Trishear 4.5、Gocad以及Trishear3D软件构建一系列不同滑移量的断层转折褶皱和断层传播褶皱的二维正演剖面,通过连接一系列不同排列方式的二维剖面建立了三种不同逆冲滑移方向的断层转折褶皱和断层传播褶皱的假三维模型,通过不同假三维模型的比较分析来探讨斜向逆冲断层相关褶皱的构造几何学特征。研究发现,斜向逆冲断层相关褶皱区别于正向逆冲断层相关褶皱的特征主要有两点:①正向逆冲断层相关褶皱层面等高线图上的最高点与后翼等高线中点的连线以及水平切面上的核心点与后翼中点的连线方向均与断层走向垂直,而斜向逆冲断层相关褶皱的最高点以及核心点与后翼中点的连线方向均与断层走向斜交,并且最高点与后翼等高线中点的连线方向或者核心点与后翼中点的连线方向均与逆冲滑移方向一致;②在褶皱平行断层走向纵剖面上,正向逆冲断层相关褶皱各个层面最高点的连线是直立的,而斜向逆冲断层相关褶皱各个层面最高点的连线发生倾斜。通过这两个特征可以判别褶皱是否存在斜向逆冲以及逆冲的方向。将模型分析结果运用到四川盆地西南部三维地震勘探资料所覆盖的邛西背斜和大兴西背斜的实例中。研究结果表明,两个背斜均存在右旋斜向逆冲,逆冲方向与各自断层走向的夹角均为70°左右,邛西背斜和大兴西背斜的逆冲方向分别是NE79°和NE77°左右,这与龙门山南段晚上新世以来的主应力方向以及反演的汶川地震最大主应力方向一致。
Oblique thrusting is widespread in nature and it is important to analyze the structural geometry of oblique-thrust fault-related-fold and identify whether oblique thrusting exists or not. The pseudo-3D models of faultbend-fold and fault-propagation-fold with different slip directions are constructed by linking a series of 2D forward cross-sections which are built by Trishear4. 5,Gocad and Trishear3D programs to discuss the structural geometry of oblique-thrust fault-related-folds. The results indicate that there are two main distinctions between oblique-thrust fault-related-folds and dip-thrust fault-related-folds. One distinction is that the line linking peak point and midpoint of back limb in the contour map or the line linking core point and midpoint of back limb in the horizontal slice of dip-thrust fault-related-folds is perpendicular to fault strike while the similar line is not perpendicular to fault strike in oblique-thrust fault-related-folds and the line is parallel to slip vector. The other distinction is that the line connecting every peak point of all bedding planes on the cross-sections parallel to fault strike is vertical in dip-thrust fault-related-folds while the line would be oblique to horizontal plane if oblique thrusting exists. The two distinctions can be used to identify whether oblique thrusting exists or not and estimate the slip directions of fault-related-folds.Qiongxi and Daxingxi anticline covered by 3D seismic data in the southwest of Sichuan basin are chosen as two examples for the research. This research indicates that oblique thrusting exists in two anticlines and the intersection angles between slip direction and fault strike are both about 70°. The slip vectors of Qiongxi anticline and Daxingxi anticline are about NE79°and NE77°respectively,which is consistent with the stress field of Longmen Shan since the late Pliocene and the most compressive stress direction inferred from coseismic slip of the Wenchuan earthquake.
Oblique thrusting is widespread in nature and it is important to analyze the structural geometry of oblique-thrust fault-related-fold and identify whether oblique thrusting exists or not. The pseudo-3D models of faultbend-fold and fault-propagation-fold with different slip directions are constructed by linking a series of 2D forward cross-sections which are built by Trishear4. 5,Gocad and Trishear3D programs to discuss the structural geometry of oblique-thrust fault-related-folds. The results indicate that there are two main distinctions between oblique-thrust fault-related-folds and dip-thrust fault-related-folds. One distinction is that the line linking peak point and midpoint of back limb in the contour map or the line linking core point and midpoint of back limb in the horizontal slice of dip-thrust fault-related-folds is perpendicular to fault strike while the similar line is not perpendicular to fault strike in oblique-thrust fault-related-folds and the line is parallel to slip vector. The other distinction is that the line connecting every peak point of all bedding planes on the cross-sections parallel to fault strike is vertical in dip-thrust fault-related-folds while the line would be oblique to horizontal plane if oblique thrusting exists. The two distinctions can be used to identify whether oblique thrusting exists or not and estimate the slip directions of fault-related-folds.Qiongxi and Daxingxi anticline covered by 3D seismic data in the southwest of Sichuan basin are chosen as two examples for the research. This research indicates that oblique thrusting exists in two anticlines and the intersection angles between slip direction and fault strike are both about 70°. The slip vectors of Qiongxi anticline and Daxingxi anticline are about NE79°and NE77°respectively,which is consistent with the stress field of Longmen Shan since the late Pliocene and the most compressive stress direction inferred from coseismic slip of the Wenchuan earthquake.
引文
杜义,谢富仁,张效亮,荆振杰.2009.汶川Ms8.0级地震断层滑动机制研究.地球物理学报,2(52):464～473.
管树巍,汪新,杨树锋,赵卫东,徐峰,雷刚林.2003.南天山库车秋里塔格褶皱带三维构造分析.地质论评,49(5):464～473.
何登发,Suppe J,贾承造.2005.断层相关褶皱理论与应用研究新进展.地学前缘,12(4):353～364.
贾东,李一泉,王毛毛,李海滨.2011.断层相关褶皱的三维构造几何学分析:以川西三维地震工区为例.岩石学报,27(3):732～740.
李一泉,贾东,罗良,贾秋鹏,陈竹新,邓飞,孙圣思.2007.川西盐井沟断层传播褶皱的三维构造建模和磁组构分析.地学前缘,4(14):74～84.
李涛,陈杰,黄明达,余松.2009.逆断层型地震地表破裂带滑动矢量计算方法探讨.第四纪研究,29(3):524～533.
魏国齐,李本亮,肖安成,陈汉林,杨树锋.2005.柴达木盆地北缘走滑—冲断构造特征及其油气勘探思路.地学前缘,12(4):397 ～402.
吴珍汉,胡道功,吴中海,叶培盛,周春景.2009.柴达木盆地北缘第四纪左旋斜冲推覆构造运动.第四纪研究,29(3).
徐嘉炜.1995.论走滑断层作用的几个主要问题.地学前缘,2(2):125 ～136.
Allmendinger R W.1998.Inverse and forward numerical modeling of trishear fault-propagation folds.Tectonics,17(4):640～656.
Brown A R.1999.Interpretation of three-dimensional seismic data.American Association of Petroleum Geologists and the Society of Exploration Geophysicists,103～156.
Cooper K and Hardy S.1999.The interaction between fault-related folding and sedimentation in 3D.Thrust Tectonics Conference,Royal Holloway,University of London.Abstract,156.Cristallini E O and Allmendinger R W.2001.Pseudo 3-D modeling of trishear fault-propagation folding.Journal of Structural Geology,23:1～2.
Cristallini E O,Giambiagi L,Allmendinger R W.2004.True threedimensional trishear:A kinematic model for strike-slip and obliqueslip deformation.Geological Society of America Bulletin,116(7～8 ):938～952.
Cardozo N.2008.Trishear in 3D.Algorithms,implementation,and limitations.Journal of Structural Geology,30:327～340.
Erslev E A.1991.Trishear fault-propagation folding.Geology,19:617～620.
Fischer M P and Wilkerson M S.2000.Predicting the orientation of joints from fold shape:Results of pseudo-three-dimensional modeling and curvature analysis.Geology,28(1):15～18.
Hardy S and Ford M.1997.Numerical modeling of trishear faultpropagation folding.Tectonics,16:841～854.
Jia Qiupeng,Jia Dong,Luo Liang,Chen Zhuxin,Li Yiquan,Deng Fei,Sun Shengsi,Li Haibin.2009.Three-dimensional evolutionary models of the Qiongxi structures,Southwestern Sichuan basin,China:Evidence from seismic interpretation and geomorphology.Acta Geologica Sinica,83(2):372～385.
Kaven J O,Maerten F,Pollard D D.2011.Mechanical analysis of fault slip data:Implications for paleostress analysis.Journal of Structural Geology,33(2):78～91.
Keating D P,Fischer M P and Blau H.2012.Physical modeling of deformation patterns in monoclines above oblique-slip faults.Journal of Structural Geology,39:37～51.
Luna L M,Hetland E A.2013.Regional stresses from coseismic slip models of the 2008 Mw 7.9 Wenchuan,China,earthquake.Tectonophysics,584:43～53.
Li Zhigang,Jia Dong,Chen Wei,Yin Hongwei,Li Shiqin,Li Yiquan,Li Haibin,Jian Gaoming,Zhou Xiaojun,Zhang Meng,Shen Li,Sun Chuan,Zhang Yong,Cui Jian.2013.Late Cenozoic east—west crustal shortening in the southern Longmen Shan range front,eastern Tibet:Implications for regional stress field changes.Tectonophysics,under review.
Suppe J.1983.Geometry and Kinematics of fault-bend folding.American Journal of Science,283:684～721.
Scholz C H.1990.The Mechanics of Earthquakes and Faulting.Cambridge University Press,Cambridge,439pp.
Tindall S E and Davis G H.1999.Monocline development by obliqueslip fault-propagation folding:the East Kaibab monocline,Colorado Plateau,Utah.Journal of Structural Geology,21:1303～1320.
Tetreault J,Jones C H,Erslev E,Larson S,Hudson M,Holdaway S.2008.Paleomagnetic and structural evidence for oblique slip in a fault-related-fold,Grayback monocline,Colorado Geological Society of America Bulletin,120(7～8):877～892.
Wilkerson M S,Medwedeff D A and Marshak S.1991.Geometrical modeling of fault-related folds:A pseudo-three-dimensional approach.Journal of Structural Geology,13(7):801～812.
Wang Maomao,Jia Dong,Lin Aiming,Shen Li,Rao Gang,Li Yiquan.2013.Late Holocene activity and historical earthquakes of the Qiongxi thrust fault system in the southern Longmen Shan fold-andthrust belt,eastern Tibetan Plateau.Tectonophysics,584:102～113.
Wang Maomao,Jia Dong,Shaw J H,Hubbard J,Lin Aiming,Li Yiquan,Shen Li.2013.Active fault-related folding beneath an alluvial terrace in the southern Longmen Shan range front,Sichuan basin,China:Implications for seismic hazard.Bulletin of the Seismological Society of America,in press.
Xu Xiwei,Wen Xueze,Yu Guihua,Chen Guihua,Klinger Y,Hubbard J,Shaw J.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 Mw7.9 Wenchuan earthquake,China.Geology,37(6):515～518.
管树巍,汪新,杨树锋,赵卫东,徐峰,雷刚林.2003.南天山库车秋里塔格褶皱带三维构造分析.地质论评,49(5):464～473.
何登发,Suppe J,贾承造.2005.断层相关褶皱理论与应用研究新进展.地学前缘,12(4):353～364.
贾东,李一泉,王毛毛,李海滨.2011.断层相关褶皱的三维构造几何学分析:以川西三维地震工区为例.岩石学报,27(3):732～740.
李一泉,贾东,罗良,贾秋鹏,陈竹新,邓飞,孙圣思.2007.川西盐井沟断层传播褶皱的三维构造建模和磁组构分析.地学前缘,4(14):74～84.
李涛,陈杰,黄明达,余松.2009.逆断层型地震地表破裂带滑动矢量计算方法探讨.第四纪研究,29(3):524～533.
魏国齐,李本亮,肖安成,陈汉林,杨树锋.2005.柴达木盆地北缘走滑—冲断构造特征及其油气勘探思路.地学前缘,12(4):397 ～402.
吴珍汉,胡道功,吴中海,叶培盛,周春景.2009.柴达木盆地北缘第四纪左旋斜冲推覆构造运动.第四纪研究,29(3).
徐嘉炜.1995.论走滑断层作用的几个主要问题.地学前缘,2(2):125 ～136.
Allmendinger R W.1998.Inverse and forward numerical modeling of trishear fault-propagation folds.Tectonics,17(4):640～656.
Brown A R.1999.Interpretation of three-dimensional seismic data.American Association of Petroleum Geologists and the Society of Exploration Geophysicists,103～156.
Cooper K and Hardy S.1999.The interaction between fault-related folding and sedimentation in 3D.Thrust Tectonics Conference,Royal Holloway,University of London.Abstract,156.Cristallini E O and Allmendinger R W.2001.Pseudo 3-D modeling of trishear fault-propagation folding.Journal of Structural Geology,23:1～2.
Cristallini E O,Giambiagi L,Allmendinger R W.2004.True threedimensional trishear:A kinematic model for strike-slip and obliqueslip deformation.Geological Society of America Bulletin,116(7～8 ):938～952.
Cardozo N.2008.Trishear in 3D.Algorithms,implementation,and limitations.Journal of Structural Geology,30:327～340.
Erslev E A.1991.Trishear fault-propagation folding.Geology,19:617～620.
Fischer M P and Wilkerson M S.2000.Predicting the orientation of joints from fold shape:Results of pseudo-three-dimensional modeling and curvature analysis.Geology,28(1):15～18.
Hardy S and Ford M.1997.Numerical modeling of trishear faultpropagation folding.Tectonics,16:841～854.
Jia Qiupeng,Jia Dong,Luo Liang,Chen Zhuxin,Li Yiquan,Deng Fei,Sun Shengsi,Li Haibin.2009.Three-dimensional evolutionary models of the Qiongxi structures,Southwestern Sichuan basin,China:Evidence from seismic interpretation and geomorphology.Acta Geologica Sinica,83(2):372～385.
Kaven J O,Maerten F,Pollard D D.2011.Mechanical analysis of fault slip data:Implications for paleostress analysis.Journal of Structural Geology,33(2):78～91.
Keating D P,Fischer M P and Blau H.2012.Physical modeling of deformation patterns in monoclines above oblique-slip faults.Journal of Structural Geology,39:37～51.
Luna L M,Hetland E A.2013.Regional stresses from coseismic slip models of the 2008 Mw 7.9 Wenchuan,China,earthquake.Tectonophysics,584:43～53.
Li Zhigang,Jia Dong,Chen Wei,Yin Hongwei,Li Shiqin,Li Yiquan,Li Haibin,Jian Gaoming,Zhou Xiaojun,Zhang Meng,Shen Li,Sun Chuan,Zhang Yong,Cui Jian.2013.Late Cenozoic east—west crustal shortening in the southern Longmen Shan range front,eastern Tibet:Implications for regional stress field changes.Tectonophysics,under review.
Suppe J.1983.Geometry and Kinematics of fault-bend folding.American Journal of Science,283:684～721.
Scholz C H.1990.The Mechanics of Earthquakes and Faulting.Cambridge University Press,Cambridge,439pp.
Tindall S E and Davis G H.1999.Monocline development by obliqueslip fault-propagation folding:the East Kaibab monocline,Colorado Plateau,Utah.Journal of Structural Geology,21:1303～1320.
Tetreault J,Jones C H,Erslev E,Larson S,Hudson M,Holdaway S.2008.Paleomagnetic and structural evidence for oblique slip in a fault-related-fold,Grayback monocline,Colorado Geological Society of America Bulletin,120(7～8):877～892.
Wilkerson M S,Medwedeff D A and Marshak S.1991.Geometrical modeling of fault-related folds:A pseudo-three-dimensional approach.Journal of Structural Geology,13(7):801～812.
Wang Maomao,Jia Dong,Lin Aiming,Shen Li,Rao Gang,Li Yiquan.2013.Late Holocene activity and historical earthquakes of the Qiongxi thrust fault system in the southern Longmen Shan fold-andthrust belt,eastern Tibetan Plateau.Tectonophysics,584:102～113.
Wang Maomao,Jia Dong,Shaw J H,Hubbard J,Lin Aiming,Li Yiquan,Shen Li.2013.Active fault-related folding beneath an alluvial terrace in the southern Longmen Shan range front,Sichuan basin,China:Implications for seismic hazard.Bulletin of the Seismological Society of America,in press.
Xu Xiwei,Wen Xueze,Yu Guihua,Chen Guihua,Klinger Y,Hubbard J,Shaw J.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 Mw7.9 Wenchuan earthquake,China.Geology,37(6):515～518.
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