俯冲带耦合作用对苏门答腊地区应变场影响的三维数值模拟
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摘要
采用有限元方法模拟了俯冲带耦合作用对巽他弧及其邻区的影响.根据模拟结果,对比GPS、地震和地质学观测数据,定量分析了苏门答腊及其周边地区的应变强度和主应变方向的分布特征,据此探讨了该区构造特征、地震发生模式与耦合面积之间的关系.模型由具有黏弹性性质的岩石圈和软流圈上地幔组成,其中岩石圈包括了大陆岩石圈和大洋岩石圈以及俯冲至上地幔中的俯冲板片.研究结果如下:(1)通过对不同俯冲带耦合面积模拟,发现苏门答腊前弧伴随耦合面积的增加应变强度逐渐增大,而增大的应变强度又影响了其周边地区的应变分布特征,因此整个苏门答腊前弧呈现出明显的分段性,这与该区地震破裂模式有较好的对应.(2)苏门答腊北部地区主应变方向与南部相比存在一定的差异,该差异是俯冲带的俯冲方向、俯冲速度、俯冲形态以及不同区域间耦合面积共同作用的结果.(3)虽然苏门答腊2004年地震主震区处于弱耦合状态,但从本文模拟的结果中可以看到,在俯冲作用下该区依然存在垂直向下的位移,这为地震激发海啸提供了有利的构造环境.
The effect of subduction coupling zone on the Sunda fore-arc and its surrounding area is modeled using finite element analysis.Based on the simulation results,which are compared with GPS survey,seismological data and geological analysis,we quantitatively analyze the distribution of strain intensity and direction of principal strain of the Sumatra and its surrounding area.Then, the relationship between the area of subduction coupling zone and tectonic evolution is discussed accordingly.The model consists of lithosphere and upper mantle of athenosphere with viscoplasticity properties.The lithosphere includes the continental lithospheric,the oceanic lithospheric and subducted slabs.The results are as follows:(1) by adjusting the area of subduction coupling zone,we find out that with coupling area increasing,the value of strain intensity tends to increase.Meanwhile,the distribution of strain field in the other areas can be affected by increase of strain intensity.Therefore,the Sumatra fore-arc shows an obvious segmentation of strain intensity,which corresponds to the rupture pattern of the Sumatra earthquake belt.(2) There is a difference in principal direction of strain between the north and the south of Sumatra,which results from the integrated effects of various subduction velocity, direction,configuration and coupling area in different regions along the subduction zone.(3) Although the northern Sumatra is in a weak coupling condition based on our simulation results, there still exists a vertical negative displacement influenced by the subduction.This result shows that this area is a tectonic environment of the development of tsunami after earthquake.
The effect of subduction coupling zone on the Sunda fore-arc and its surrounding area is modeled using finite element analysis.Based on the simulation results,which are compared with GPS survey,seismological data and geological analysis,we quantitatively analyze the distribution of strain intensity and direction of principal strain of the Sumatra and its surrounding area.Then, the relationship between the area of subduction coupling zone and tectonic evolution is discussed accordingly.The model consists of lithosphere and upper mantle of athenosphere with viscoplasticity properties.The lithosphere includes the continental lithospheric,the oceanic lithospheric and subducted slabs.The results are as follows:(1) by adjusting the area of subduction coupling zone,we find out that with coupling area increasing,the value of strain intensity tends to increase.Meanwhile,the distribution of strain field in the other areas can be affected by increase of strain intensity.Therefore,the Sumatra fore-arc shows an obvious segmentation of strain intensity,which corresponds to the rupture pattern of the Sumatra earthquake belt.(2) There is a difference in principal direction of strain between the north and the south of Sumatra,which results from the integrated effects of various subduction velocity, direction,configuration and coupling area in different regions along the subduction zone.(3) Although the northern Sumatra is in a weak coupling condition based on our simulation results, there still exists a vertical negative displacement influenced by the subduction.This result shows that this area is a tectonic environment of the development of tsunami after earthquake.
引文
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[5] Hall R.Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific:computer-based reconstructions and animations.J.Asian Earth Sci.,2002,20(4) :353～434
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[12] Shapiro N M,Michael H R,Engdah E R.Structural context of the great Sumatra-Andaman Islands earthquake.Geophys.Res.Lett.,2008,35,L05301,doi:10． 1029/2008GL033381
[13] Deplus C,Diament M,Hebert H,et al.Direct evidence of active deformation in the eastern Indian Ocean plate.Geology,1998,26:131～134
[14] Hebert H,Villemant B,Deplus C,et al.Contrasting geophysical and geochemical signatures of a volcano at the axis of the Wharton fossil ridge(N-E Indian Ocean).Geophys.Res.Lett.,1999,26:1053～1056
[15] Malod J A,Kemal B M.The Sumatra margin:oblique subduction and lateral displacement of the accretionary prism.In:Hall R,Blundell D J eds.Tectonic Evolution of Southeast Asia.Geol.Soc.Special Publication,1996,106:19～28
[16] Baroux E,Avouac J P,Bellier O,et al.Slip-partitioning and fore-arc deformation at the Sunda Trench,Indonesia.Terra Nova,1998,10(3) :139～144
[17] McCaffrey R,Zwick P,Bock Y,et al.Strain partitioning during oblique plate convergence in northern Sumatra:geodetic and seismologic constraints and numerical modeling.J.Geophys.Res.,2000,105(28) :363～376
[18] McCaffrey R.Oblique plate convergence,slip vectors,and fore arc deformation.J.Geophys.Res.,1992,97(B6) :8905～8912
[19] Curray J R,Moore D G,Lawver L A,et al.Tectonics of the Andaman Sea and Burma.In:Watkins J S,Montaert L,Doclerson P ed.Geological and Geophysical Investigations of Continental Margins.Mem.Am.Assoc.Pet.Geol.,1979,29:189～198
[20] Rodolfo K S.Bathymetry and Marine geology of Andaman Basin,and tectonics implications for Southeast Asia.Geol.Soc.Am.Bull.,1996,80:1203～1230
[21] Maung H.Transcurrent movements in the Burma-Andaman sea region.Geology,1987,15:911～912
[22] Jarrad R D.Relations among subduction parameters.Rev.Geophys.,1986,24:217～284
[23] Lawyer L A,Curray J R.Evolution of the Andaman sea.Eos,Trans.Am.Geophys.Union,1981,62:1044
[24] 陶春辉,戴黎明,孙耀等.印尼附近海域地震海啸发生的构造背景综述.海洋学研究,2008,26(2) :59～66 Tao C H,Dai L M,Sun Y,et al.Summary on the tectonic setting of the area around Indonesia where earthquake tsunami happened.Journal of Marine Sciences(in Chinese),2008,26(2) :59～66
[25] Billen I B,Gurnis M.A low viscosity wedge in subduction zones.Earth Planet.Sci.Lett.,2001,193:227～236
[26] Radhakrishna M,Lasitha S,Mukhopadhyay M.Seismicity,gravity anomalies and lithospheric structure of the Andaman arc,NE Indian Ocean.Tectonophysics,2008,460:248～262
[27] Kennetta B L N,Cumminsb P R.The relationship of the seismic source and subduction zone structure for the 2004 December 26 Sumatra Andaman earthquake.Earth Planet.Sci.Lett.,2005,239:1～8
[28] Mitchell A H G.Phanerozoic plate boundaries in mainland SE Asia,the Himalayas and Tibet.J.Geol.Soc.London,1981,138:109～122
[29] Maung H.The active tectonics in the eastern Himalayan syntaxis and surrounding region.Geology,1989,15:903～906
[30] Posacev M,Taylor D,Leeuwen T,et al.Tectonic controls of vulcanism and complex movements along the Sumatra fault system.Geol.Soc.Malaysia Bull.,1973,6:43～60
[31] Tjia H D.Tectonic depressions along the transcurrent Sumatra fault zone.Geol.Indonesia,1977,4:13～27
[32] Wang J,Ye Z R,He J K.Three-dimensional mechanical modeling of large-scale crustal deformation in China constrained by the GPS velocity field.Tectonophysics,2008,446:51～56
[33] He J K,Jean C.Slip rates of the Altyn Tagh,Kunlun and Karakorum faults(Tibet)from 3D mechanical modeling.Earth Planet.Sci.Lett.,2008,274:50～58
[34] 钟增球,索书田,张利等.岩石塑性流变学--大别-苏鲁高压超高压变质带的构造学.中国地质大学出版社,2007． 8～10 Zhong Z Q,Suo S T,Zhang L,et al.Plastic Rheology of Rocks-A Structural Study on the Dabie-Sulu UHP and HP Metamorphic Belts(in Chinese).China University of Geosciences Press,2007． 8～10
[35] 石耀霖,曹建玲.中国大陆岩石圈等效粘滞系数的计算和讨论.地学前缘,2008,15(3) :82～95 Shi Y L,Cao J L.Effective viscosity of China continental lithosphere.Earth Science Frontiers(in Chinese),2008,15(3) :82～95
[36] 郑勇,傅容珊,熊熊.中国大陆及周边地区现代岩石圈演化动力学模拟.地球物理学报,2006,49(2) :415～427 Zheng Y,Fu R S,Xiong X.Dynamic simulation of lithospheric evolution from the modern China mainland and its surrounding areas.Chinese J.Geophys.(in Chinese),2006,49(2) :415～427
[37] Karato S,Wu P.Rheology of the upper mantle:a synthesis.Science,1993,260:771～778
[38] Freed A M,Burgmann R.Evidence of power-law flow in the Mojave desert mantle.Nature,2004,430:548～551
[39] Franco D,Govers R,Wortel R.Numerical comparison of different convergent plate contacts:subduction channel and subduction fault.Geophys.J.Int.,2007,271(1) :435～450
[40] Chamot-Rooke N,Pichona X L.GPS determined eastward Sunda land motion with respect to Eurasia confirmed by earthquakes slip vectors at Sunda and Philippine trenches.Earth Planet.Sci.Lett.,1999,173:439～455
[41] Gero W M,Yu Y Q,Zhu S Y.Crustal motion and block behaviour in SE-Asia from GPS measurements.Earth Planet.Sci.Lett.,2001,187:239～244
[42] Mosher D C,Austin J A,Fisher J.Deformation of the northern Sumatra accretionary prism from high-resolution seismic reflection profiles and ROV observations.Marine Geol.,2008,252:89～99
[43] Malod J A,Komar Karta,Besier M O.From normal to oblique subduction:tectonic relationships between Java and Sumatra.Jour.Southeast Asia.Earth Sci.,1995,12(2) :85～93
[44] Giancarlo S.Geodynamics of the Wadati-Benioff zone earthquakes:The 2004 Sumatra earthquake and other great earthquakes.Geofisica Internacional,2007,46(1) :19～50
[45] Ghose R,Yoshioka S,Oike K.Three-dimensional numerical simulation of the subduction dynamics in the Sunda arc region,Southeast Asia.Tectonophysics,1990,181:223～255
[2] Wiens D A,DeMets C,Gordan R G,et al.A diffuse plate boundary model for Indian Ocean tectonics.Geophys.Res.Lett.,1985,12:429～432
[3] DeMets C,Gordon R G,Argus G F,et al.Current plate motions.Am.Assoc.pet.Geol.Bull.,1990,57:2452～2456
[4] Anne R,Hrafnkell K,Rob D,et al.4-D evolution of SE Asia's mantle from geological reconstructions and seismic tomography.Earth Planet.Sci.Lett.,2004,221:103～115
[5] Hall R.Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific:computer-based reconstructions and animations.J.Asian Earth Sci.,2002,20(4) :353～434
[6] Curray J R,Moore D G,Lawver L A,et al.Tectonics of the Andaman Sea and Burma.In..Watkins J,Montadert L,Dickerson P W eds.Geological and Geophysical Investigations of Continental Margins.American Association Petroleum Geologists,1979,Memoir 29:189～198
[7] Curray J R.Tectonics and history of the Andaman Sea region.J.Asian Earth Sci.,2005,25:187～232
[8] Khan P K,Chakraborty P P.Two-phase opening of Andaman Sea:a new seismotectonic insight.Earth Planet.Sci.Lett.,2005,229:259～271
[9] 朱守彪,邢会林,谢富仁等.地震发生过程的有限单元法模拟--以苏门答腊俯冲带上的大地震为例.地球物理学报,2008,51(2) :460～468 Zhu S B,Xing H L,Xie F R,et al.Simulation of earthquake processes by finite element method:The case of megathrust earthquakes on the Sumatra subduction zone.Chinese J.Geophys.(in Chinese),2008,51(2) :460～468
[10] Grevemeyer I,Tiwari V M.Overriding plate controls spatial distribution of megathrust earthquakes in the Sunda-Andaman subduction zone.Earth Planet.Sci.Lett.,2006,251:199～208
[11] Chlieh M,Avouac J P,Sieh K,et al.Heterogeneous coupling of the Sumatran megathrust constrained by geodetic and paleogeodetic measurements.J.Geophys.Res.,2008,113,B05305,doi:10． 1029/2007JB004981
[12] Shapiro N M,Michael H R,Engdah E R.Structural context of the great Sumatra-Andaman Islands earthquake.Geophys.Res.Lett.,2008,35,L05301,doi:10． 1029/2008GL033381
[13] Deplus C,Diament M,Hebert H,et al.Direct evidence of active deformation in the eastern Indian Ocean plate.Geology,1998,26:131～134
[14] Hebert H,Villemant B,Deplus C,et al.Contrasting geophysical and geochemical signatures of a volcano at the axis of the Wharton fossil ridge(N-E Indian Ocean).Geophys.Res.Lett.,1999,26:1053～1056
[15] Malod J A,Kemal B M.The Sumatra margin:oblique subduction and lateral displacement of the accretionary prism.In:Hall R,Blundell D J eds.Tectonic Evolution of Southeast Asia.Geol.Soc.Special Publication,1996,106:19～28
[16] Baroux E,Avouac J P,Bellier O,et al.Slip-partitioning and fore-arc deformation at the Sunda Trench,Indonesia.Terra Nova,1998,10(3) :139～144
[17] McCaffrey R,Zwick P,Bock Y,et al.Strain partitioning during oblique plate convergence in northern Sumatra:geodetic and seismologic constraints and numerical modeling.J.Geophys.Res.,2000,105(28) :363～376
[18] McCaffrey R.Oblique plate convergence,slip vectors,and fore arc deformation.J.Geophys.Res.,1992,97(B6) :8905～8912
[19] Curray J R,Moore D G,Lawver L A,et al.Tectonics of the Andaman Sea and Burma.In:Watkins J S,Montaert L,Doclerson P ed.Geological and Geophysical Investigations of Continental Margins.Mem.Am.Assoc.Pet.Geol.,1979,29:189～198
[20] Rodolfo K S.Bathymetry and Marine geology of Andaman Basin,and tectonics implications for Southeast Asia.Geol.Soc.Am.Bull.,1996,80:1203～1230
[21] Maung H.Transcurrent movements in the Burma-Andaman sea region.Geology,1987,15:911～912
[22] Jarrad R D.Relations among subduction parameters.Rev.Geophys.,1986,24:217～284
[23] Lawyer L A,Curray J R.Evolution of the Andaman sea.Eos,Trans.Am.Geophys.Union,1981,62:1044
[24] 陶春辉,戴黎明,孙耀等.印尼附近海域地震海啸发生的构造背景综述.海洋学研究,2008,26(2) :59～66 Tao C H,Dai L M,Sun Y,et al.Summary on the tectonic setting of the area around Indonesia where earthquake tsunami happened.Journal of Marine Sciences(in Chinese),2008,26(2) :59～66
[25] Billen I B,Gurnis M.A low viscosity wedge in subduction zones.Earth Planet.Sci.Lett.,2001,193:227～236
[26] Radhakrishna M,Lasitha S,Mukhopadhyay M.Seismicity,gravity anomalies and lithospheric structure of the Andaman arc,NE Indian Ocean.Tectonophysics,2008,460:248～262
[27] Kennetta B L N,Cumminsb P R.The relationship of the seismic source and subduction zone structure for the 2004 December 26 Sumatra Andaman earthquake.Earth Planet.Sci.Lett.,2005,239:1～8
[28] Mitchell A H G.Phanerozoic plate boundaries in mainland SE Asia,the Himalayas and Tibet.J.Geol.Soc.London,1981,138:109～122
[29] Maung H.The active tectonics in the eastern Himalayan syntaxis and surrounding region.Geology,1989,15:903～906
[30] Posacev M,Taylor D,Leeuwen T,et al.Tectonic controls of vulcanism and complex movements along the Sumatra fault system.Geol.Soc.Malaysia Bull.,1973,6:43～60
[31] Tjia H D.Tectonic depressions along the transcurrent Sumatra fault zone.Geol.Indonesia,1977,4:13～27
[32] Wang J,Ye Z R,He J K.Three-dimensional mechanical modeling of large-scale crustal deformation in China constrained by the GPS velocity field.Tectonophysics,2008,446:51～56
[33] He J K,Jean C.Slip rates of the Altyn Tagh,Kunlun and Karakorum faults(Tibet)from 3D mechanical modeling.Earth Planet.Sci.Lett.,2008,274:50～58
[34] 钟增球,索书田,张利等.岩石塑性流变学--大别-苏鲁高压超高压变质带的构造学.中国地质大学出版社,2007． 8～10 Zhong Z Q,Suo S T,Zhang L,et al.Plastic Rheology of Rocks-A Structural Study on the Dabie-Sulu UHP and HP Metamorphic Belts(in Chinese).China University of Geosciences Press,2007． 8～10
[35] 石耀霖,曹建玲.中国大陆岩石圈等效粘滞系数的计算和讨论.地学前缘,2008,15(3) :82～95 Shi Y L,Cao J L.Effective viscosity of China continental lithosphere.Earth Science Frontiers(in Chinese),2008,15(3) :82～95
[36] 郑勇,傅容珊,熊熊.中国大陆及周边地区现代岩石圈演化动力学模拟.地球物理学报,2006,49(2) :415～427 Zheng Y,Fu R S,Xiong X.Dynamic simulation of lithospheric evolution from the modern China mainland and its surrounding areas.Chinese J.Geophys.(in Chinese),2006,49(2) :415～427
[37] Karato S,Wu P.Rheology of the upper mantle:a synthesis.Science,1993,260:771～778
[38] Freed A M,Burgmann R.Evidence of power-law flow in the Mojave desert mantle.Nature,2004,430:548～551
[39] Franco D,Govers R,Wortel R.Numerical comparison of different convergent plate contacts:subduction channel and subduction fault.Geophys.J.Int.,2007,271(1) :435～450
[40] Chamot-Rooke N,Pichona X L.GPS determined eastward Sunda land motion with respect to Eurasia confirmed by earthquakes slip vectors at Sunda and Philippine trenches.Earth Planet.Sci.Lett.,1999,173:439～455
[41] Gero W M,Yu Y Q,Zhu S Y.Crustal motion and block behaviour in SE-Asia from GPS measurements.Earth Planet.Sci.Lett.,2001,187:239～244
[42] Mosher D C,Austin J A,Fisher J.Deformation of the northern Sumatra accretionary prism from high-resolution seismic reflection profiles and ROV observations.Marine Geol.,2008,252:89～99
[43] Malod J A,Komar Karta,Besier M O.From normal to oblique subduction:tectonic relationships between Java and Sumatra.Jour.Southeast Asia.Earth Sci.,1995,12(2) :85～93
[44] Giancarlo S.Geodynamics of the Wadati-Benioff zone earthquakes:The 2004 Sumatra earthquake and other great earthquakes.Geofisica Internacional,2007,46(1) :19～50
[45] Ghose R,Yoshioka S,Oike K.Three-dimensional numerical simulation of the subduction dynamics in the Sunda arc region,Southeast Asia.Tectonophysics,1990,181:223～255
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