海山俯冲过程中的变形特征——物理模拟和数值模拟证据
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摘要
文章通过物理模拟和数值模拟相结合的方法,探讨了海山在俯冲过程中自身出现的变化特征。结果表明,海山在增生楔体中俯冲时,主要变化特征表现为其上覆的大洋沉积物的刮落,唯有海山尾部的洋壳有小部分大洋沉积物得以保存;当海山开始进入俯冲通道时,海山逐渐由向陆壳之下硬挤入变为向地幔挠曲,而向地幔的挠曲变形为海山进入俯冲提供了充足的空间并使俯冲洋壳的俯冲角度增加。俯冲挠曲过程有效降低了陆壳与海山之间的耦合度,从而降低大震的发生概率。此外,文章也对多手段研究俯冲带变形的尝试进行了探讨。
Using sandbox experiment and numerical simulation,we discussed deformation of a subducting seamount. Our results showed that the deformation mainly concentrated at the overlain ocean sediment when a seamount subducted beneath the accretionary wedge. The sediment was scraped into wedge,while the part in the tailing of the seamount was well stored. After the seamount entered the subduction channel,the oceanic crust began to bend downward. The bending provided more space for seamount subduction and caused the subduction angle increased. Above described subduction process decreased the coupling between seamount and continental crust,leading to occurrences of megathrust earthquakes largely reduced. This study also represented an attempt to investigate deformation of a subduction zone by multi-methods.
Using sandbox experiment and numerical simulation,we discussed deformation of a subducting seamount. Our results showed that the deformation mainly concentrated at the overlain ocean sediment when a seamount subducted beneath the accretionary wedge. The sediment was scraped into wedge,while the part in the tailing of the seamount was well stored. After the seamount entered the subduction channel,the oceanic crust began to bend downward. The bending provided more space for seamount subduction and caused the subduction angle increased. Above described subduction process decreased the coupling between seamount and continental crust,leading to occurrences of megathrust earthquakes largely reduced. This study also represented an attempt to investigate deformation of a subduction zone by multi-methods.
引文
李付成,孙珍,张云帆,等,2012.海山的倾斜俯冲对上覆板块变形的影响[J].地球物理学进展,27:1406-1415.LI F C,SUN Z,ZHANG Y F,et al,2012.Influence of oblique seamount subduction on the deformation of upper plate[J].Progress in Geophys,27(4):1406-1415.
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朱守彪,邢会林,谢富仁,等,2008.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[J].地球物理学报,51:460-468.ZHU S B,XING H L,XIE F R,et al,2008.Simulation of earthquake processes by finite element method:The case of megathrust earthquakes on the Sumatra subduction zone[J].Chinese Journal of Geophysics,2008,51(2):460-468.
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BANGS N L B,GULICK S P S,SHIPLEY T H,2006.Seamount subduction erosion in the Nankai Trough and its potential impact on the seismogenic zone[J].Geology,34:701.
BILEK S L,2007.Influence of subducting topography on earthquake rupture[J].The Seismogenic Zone of Subduction Thrust Faults:123-146.
CLOOS M,1992.Thrust-type subduction-zone earthquakes and seamount asperities:A physical model for seismic rupture[J].Geology,20:601.
COULBOURN W T,HILL P J,BERGERSEN D D,1989.Machias Seamount,Western Samoa:Sediment remobilization,tectonic dismemberment and subduction of a guyot[J].Geo-marine letters,9:119-125.
DOMINGUEZ S,LALLEMAND S,MALAVIEILLE J,et al,1998.Upper plate deformation associated with seamount subduction[J].Tectonophysics,293:207-224.
DOMINGUEZ S,MALAVIEILLE J,LALLEMAND S,2000.Deformation of accretionary wedges in response to seamount subduction:Insights from sandbox experiments[J].Tectonics,19:182-196.
FRYER P,AMBOS E L,HUSSONG D M,1985.Origin and emplacement of Mariana forearc seamounts[J].Geology,13:774.
GAO X,WANG K,2014.Strength of stick-slip and creeping subduction megathrusts from heat flow observations[J].Science,345:1038-1041.
IGARASHI T,MATSUZAWA T,HASEGAWA A,2003.Repeating earthquakes and interplate aseismic slip in the northeastern Japan subduction zone[J].Journal of Geophysical Research:Solid Earth(1978-2012),108.
KELLEHER J,MCCANN W,1976.Buoyant zones,great earthquakes,and unstable boundaries of subduction[J].Journal of Geophysical Research,81:4885-4896.
KODAIRA S,2000.Subducted Seamount Imaged in the Rupture Zone of the 1946 Nankaido Earthquake[J].Science,289:104-106.
LALLEMAND S E,SCHN RLE P,MALAVIEILLE J,1994.Coulomb theory applied to accretionary and nonaccretionary wedges:Possible causes for tectonic erosion and/or frontal accretion[J].Journal of Geophysical Research:Solid Earth(1978-2012),99:12033-12055.
LI F,SUN Z,HU D,et al,2013.Crustal structure and deformation associated with seamount subduction at the north Manila Trench represented by analog and gravity modeling[J].Marine Geophysical Research,34:393-406.
MATSUZAWA T,IGARASHI T,HASEGAWA A,2002.Characteristic small earthquake sequence off Sanriku,northeastern Honshu,Japan[J].Geophysical Research Letters,29:38-1-38-4.
NISHIZAWA A,KANEDA K,WATANABE N,et al,2009.Seismic structure of the subducting seamounts on the trench axis:Erimo Seamount and Daiichi-Kashima Seamount,northern and southern ends of the Japan Trench[J].Earth Planets Space,61:e5-e8.
ORD A,1991.Deformation of rock:a pressure-sensitive,dilatant material[J].Pure and Applied Geophysics,137:337-366.
PARK J O,TSURU T,KANEDA Y,et al,1999.A subducting seamount beneath the Nankai accretionary prism off Shikoku,southwestern Japan[J].Geophysical Research Letters,26:931-934.
PEDLEY K L,BARNES P M,PETTINGA J R,et al,2010.Seafloor structural geomorphic evolution of the accretionary frontal wedge in response to seamount subduction,Poverty Indentation,New Zealand[J].Marine Geology,270:119-138.
POLYANSKY O,KOROBEYNIKOV S,BABICHEV A,et al,2014.Numerical modeling of mantle diapirism as a cause of intracontinental rifting[J].Izvestiya,Physics of the Solid Earth,50:839-852.
SINGH S C,HANANTO N,MUKTI M,et al,2011.Aseismic zone and earthquake segmentation associated with a deep subducted seamount in Sumatra[J].Nature Geoscience,4:308-311.
SUN Z,ZHOU D,ZHONG Z,et al,2006.Research on the dynamics of the South China Sea opening:Evidence from analogue modeling[J].Science in China Series D:Earth Sciences,49:1053-1069.
WATTS A B,KOPPERS A A,ROBINSON D P,2010.Seamount subduction and earthquakes[J].Oceanography,23(1):166-173.
YAMAZAKI T,OKAMURA Y,1989.Subducting seamounts and deformation of overriding forearc wedges around Japan[J].Tectonophysics,160:207-229.
李家彪,金翔龙,阮爱国,等,2004.马尼拉海沟增生楔中段的挤入构造[J].科学通报,49(10):1000-1008.LI J B,JIN X L,RUAN A G,et al,2004.Diapiric structure of accretionary middle piece in Manila trench[J].Chinese Science Bulletin,49(10):1000-1008.
朱守彪,邢会林,谢富仁,等,2008.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[J].地球物理学报,51:460-468.ZHU S B,XING H L,XIE F R,et al,2008.Simulation of earthquake processes by finite element method:The case of megathrust earthquakes on the Sumatra subduction zone[J].Chinese Journal of Geophysics,2008,51(2):460-468.
ABERCROMBIE R E,ANTOLIK M,FELZER K,et al,2001.The 1994 Java tsunami earthquake:Slip over a subducting seamount[J].Journal of Geophysical Research:Solid Earth(1978-2012),106:6595-6607.
BABA T,HORI T,HIRANO S,et al,2001.Deformation of a seamount subducting beneath an accretionary prism:Constraints from numerical simulation[J].Geophysical Research Letters,28:1827-1830.
BANGS N L B,GULICK S P S,SHIPLEY T H,2006.Seamount subduction erosion in the Nankai Trough and its potential impact on the seismogenic zone[J].Geology,34:701.
BILEK S L,2007.Influence of subducting topography on earthquake rupture[J].The Seismogenic Zone of Subduction Thrust Faults:123-146.
CLOOS M,1992.Thrust-type subduction-zone earthquakes and seamount asperities:A physical model for seismic rupture[J].Geology,20:601.
COULBOURN W T,HILL P J,BERGERSEN D D,1989.Machias Seamount,Western Samoa:Sediment remobilization,tectonic dismemberment and subduction of a guyot[J].Geo-marine letters,9:119-125.
DOMINGUEZ S,LALLEMAND S,MALAVIEILLE J,et al,1998.Upper plate deformation associated with seamount subduction[J].Tectonophysics,293:207-224.
DOMINGUEZ S,MALAVIEILLE J,LALLEMAND S,2000.Deformation of accretionary wedges in response to seamount subduction:Insights from sandbox experiments[J].Tectonics,19:182-196.
FRYER P,AMBOS E L,HUSSONG D M,1985.Origin and emplacement of Mariana forearc seamounts[J].Geology,13:774.
GAO X,WANG K,2014.Strength of stick-slip and creeping subduction megathrusts from heat flow observations[J].Science,345:1038-1041.
IGARASHI T,MATSUZAWA T,HASEGAWA A,2003.Repeating earthquakes and interplate aseismic slip in the northeastern Japan subduction zone[J].Journal of Geophysical Research:Solid Earth(1978-2012),108.
KELLEHER J,MCCANN W,1976.Buoyant zones,great earthquakes,and unstable boundaries of subduction[J].Journal of Geophysical Research,81:4885-4896.
KODAIRA S,2000.Subducted Seamount Imaged in the Rupture Zone of the 1946 Nankaido Earthquake[J].Science,289:104-106.
LALLEMAND S E,SCHN RLE P,MALAVIEILLE J,1994.Coulomb theory applied to accretionary and nonaccretionary wedges:Possible causes for tectonic erosion and/or frontal accretion[J].Journal of Geophysical Research:Solid Earth(1978-2012),99:12033-12055.
LI F,SUN Z,HU D,et al,2013.Crustal structure and deformation associated with seamount subduction at the north Manila Trench represented by analog and gravity modeling[J].Marine Geophysical Research,34:393-406.
MATSUZAWA T,IGARASHI T,HASEGAWA A,2002.Characteristic small earthquake sequence off Sanriku,northeastern Honshu,Japan[J].Geophysical Research Letters,29:38-1-38-4.
NISHIZAWA A,KANEDA K,WATANABE N,et al,2009.Seismic structure of the subducting seamounts on the trench axis:Erimo Seamount and Daiichi-Kashima Seamount,northern and southern ends of the Japan Trench[J].Earth Planets Space,61:e5-e8.
ORD A,1991.Deformation of rock:a pressure-sensitive,dilatant material[J].Pure and Applied Geophysics,137:337-366.
PARK J O,TSURU T,KANEDA Y,et al,1999.A subducting seamount beneath the Nankai accretionary prism off Shikoku,southwestern Japan[J].Geophysical Research Letters,26:931-934.
PEDLEY K L,BARNES P M,PETTINGA J R,et al,2010.Seafloor structural geomorphic evolution of the accretionary frontal wedge in response to seamount subduction,Poverty Indentation,New Zealand[J].Marine Geology,270:119-138.
POLYANSKY O,KOROBEYNIKOV S,BABICHEV A,et al,2014.Numerical modeling of mantle diapirism as a cause of intracontinental rifting[J].Izvestiya,Physics of the Solid Earth,50:839-852.
SINGH S C,HANANTO N,MUKTI M,et al,2011.Aseismic zone and earthquake segmentation associated with a deep subducted seamount in Sumatra[J].Nature Geoscience,4:308-311.
SUN Z,ZHOU D,ZHONG Z,et al,2006.Research on the dynamics of the South China Sea opening:Evidence from analogue modeling[J].Science in China Series D:Earth Sciences,49:1053-1069.
WATTS A B,KOPPERS A A,ROBINSON D P,2010.Seamount subduction and earthquakes[J].Oceanography,23(1):166-173.
YAMAZAKI T,OKAMURA Y,1989.Subducting seamounts and deformation of overriding forearc wedges around Japan[J].Tectonophysics,160:207-229.