高温高压条件下彭灌杂岩的强度对汶川地震发震机制的启示
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摘要
采用汶川地震震源区彭灌杂岩中代表性细粒花岗岩样品,在固体围压介质三轴实验系统上开展了高温高压流变实验研究.实验的温度和压力条件按照龙门山断层带5~30km深度对应的温度和压力(静岩压)设定.利用偏光显微镜和扫描电镜对实验样品进行微观结构观察.实验结果表明,实验样品在10~20km深度都具有很高的强度,彭灌杂岩在该深度处于脆性破裂-脆塑性转化域,而在20~30km实验样品强度显著降低,彭灌杂岩进入塑性流变域,这与流变结构中的极限强度很接近.以花岗岩为代表的彭灌杂岩的破裂强度决定了中上地壳的强度,在15~20km深度不仅强度达到最大值,而且控制了断层不稳定滑动,具备地震成核条件.因此,把彭灌杂岩强度随深度变化规律与流变结构和滑动稳定性参数(a-b)结合起来得出,彭灌杂岩在15~20km的高强度是汶川地震的孕育和发生的必要条件.
Two sets of deformation experiments were performed on fine-grained granite collected from the Pengguan Complex in the solid-medium triaxial apparatus under high temperature and high pressure.Temperature and pressure conditions in the experiments were designed based on the in situ conditions of the Longmenshan fault zone at depths of 5~30 km.Microstructures of theexperimentally deformed samples were observed under polarizing microscope and scanning electron microscope(SEM).The tested samples from the two sets of experiments have high strength at conditions corresponding to a depth of 10 to 20 km,which corresponds to the brittle fracture to brittle-plastic transition domain.While the strength of the samples reduces obviously at conditions corresponding to the depth of 25 to 30 km,suggesting the samples are in the plastic flow.As a representative rock of the Pengguan Complex,granite has the strongest strength at the depth of 15 to 20 km,which is close to the ultimate strength in rheological profile.In this depth range,the rupture strength of the Pengguan Complex not only determines the strength of middle crust,but also controls unstable slide of fault,which means stick-slip of fault could happen and thus cause earthquake nucleation.Therefore,based on the strength data of the Pengguan Complex with the rheological profile and the frictional velocity dependence value(ab),we conclude that the high strength of the Pengguan Complex at the depth of 10 to 20 km is a crucial factor for the nucleation and generation of the Wenchuan earthquake.
Two sets of deformation experiments were performed on fine-grained granite collected from the Pengguan Complex in the solid-medium triaxial apparatus under high temperature and high pressure.Temperature and pressure conditions in the experiments were designed based on the in situ conditions of the Longmenshan fault zone at depths of 5~30 km.Microstructures of theexperimentally deformed samples were observed under polarizing microscope and scanning electron microscope(SEM).The tested samples from the two sets of experiments have high strength at conditions corresponding to a depth of 10 to 20 km,which corresponds to the brittle fracture to brittle-plastic transition domain.While the strength of the samples reduces obviously at conditions corresponding to the depth of 25 to 30 km,suggesting the samples are in the plastic flow.As a representative rock of the Pengguan Complex,granite has the strongest strength at the depth of 15 to 20 km,which is close to the ultimate strength in rheological profile.In this depth range,the rupture strength of the Pengguan Complex not only determines the strength of middle crust,but also controls unstable slide of fault,which means stick-slip of fault could happen and thus cause earthquake nucleation.Therefore,based on the strength data of the Pengguan Complex with the rheological profile and the frictional velocity dependence value(ab),we conclude that the high strength of the Pengguan Complex at the depth of 10 to 20 km is a crucial factor for the nucleation and generation of the Wenchuan earthquake.
引文
Chen J H,Liu Q Y,Li S C,et al.2009.Seismotectonic study by relocation of the Wenchuan MS8.0 earthquake sequence.Chinese Journal of Geophysics(in Chinese),52(2):390-397.
Chen J H,Froment B,Liu Q Y,et al.2010.Distribution of seismic wave speed changes associated with the 12 May 2008 MW7.9Wenchuan earthquake.Geophysical Research Letters,37(18):L18302,doi:10.1029/2010GL044582.
Dang J X,Zhou Y S,Rybacki E,et al.2017.An experimental study on the brittle-plastic transition during deformation of granite.Journal of Asian Earth Sciences,139:30-39,doi:10.1016/j.jseaes.2016.08.023.
Duan Q B,Yang X S,Ma S L,et al.2016.Fluid-rock interactions in seismic faults:Implications from the structures and mineralogical and geochemical compositions of drilling cores from the rupture of the 2008 Wenchuan earthquake,China.Tectonophysics,666:260-280.
Gerald J F D,Stünitz H.1993.Deformation of granitoids at low metamorphic grade.I:Reactions and grain size reduction.Tectonophysics,221(3-4):269-297.
Han L,Zhou Y S,Dang J X,et al.2009.Temperature calibration for 3Gpa molten salt medium triaxial pressure vessel.Chinese Journal of High Pressure Physics(in Chinese),25(6):407-414.
Han L,Zhou Y S,Yao W M.2013.A simulating experimental study on crack healing and the formation of high pore fluid pressure in faults of middle crust.Chinese Journal of Geophysics(in Chinese),56(1):91-105,doi:10.6038/cjg20130110.
Han L,Zhou Y S,He C R,et al.2016.Sublithostatic pore fluid pressure in the brittle-ductile transition zone of Mesozoic Yingxiu-Beichuan fault and its implication for the 2008 MW7.9Wenchuan earthquake.Journal of Asian Earth Sciences,117:107-118,doi:10.1016/j.jseaes.2015.12.009.
Liu G,Zhou Y S,Yao W M,et al.2013.Experimental study on the effect of pre-existing fabric to deformation of granitic gneiss under high temperature and pressure.Chinese Journal of Geophysics(in Chinese),56(7):2332-2347,doi:10.6038/cjg20130720.
Liu G,Zhou Y S,He C R,et al.2016.An experimental study of effect of pre-existing fabric on deformation of foliated mylonite at high temperature and pressure.Geological Journal,51(1):92-112,doi:10.1002/gj.2611.
Liu G,Zhou Y S,Shi Y L,et al.2017.Strength variation and deformational behavior in anisotropic granitic mylonites under high-temperature and-pressure conditions-an experimental study.Journal of Structural Geology,96:21-34.
Liu Q Y,Van Der Hilst R D,Li Y,et al.2014.Eastward expansion of the Tibetan Plateau by crustal flow and strain partitioning across faults.Nature Geoscience,7(5):361-365,doi:10.1038/NGEO2130.
Liu Z X,Zhou Y S,Liu G,et al.2013.Axial friction calibration for3Gpa molten salt medium triaxial pressure vessel under high pressure and high temperature.Chinese Journal of High Pressure Physics(in Chinese),27(1):19-28.
Liu-Zeng J,Zhang Z,Wen L,et al.2009.Co-seismic ruptures of the 12 May 2008,MS8.0 Wenchuan earthquake,Sichuan:East-west crustal shortening on oblique,parallel thrusts along the eastern edge of Tibet.Earth and Planetary Science Letters,286(3-4):355-370.
Pec M,Stünitz H,Heilbronner R,et al.2016.Semi-brittle flow of granitoid fault rocks in experiments.Journal of Geophysical Research:Solid Earth,121(3):1677-1705.
Trepmann C A,St9ckhert B.2003.Quartz microstructures developed during non-steady state plastic flow at rapidly decaying stress and strain rate.Journal of Structural Geology,2003,25(12):2035-2051.
Wang S Z,Zhang L.1982.Deformation and failure of Zhoukoudian granodiorite at the crustal temperature and pressure.Seismology and Geology(in Chinese),4(4):68-91.
Wang S Z,Zhang L.1984.Shear fracture and stick-slip-a study on shock-generation mechanism of strong shallow earthquakes.Seismology and Geology(in Chinese),6(2):63-73.
Wang W,Wang S Z,Cui X F.1989.Strengh Characteristics of Juyongguan granite and Jinan gabbro at geologic crustal conditions.Modern Crustal Movement Research(in Chinese),(4):163-168.
Wintsch R P,Yeh M W.2013.Oscillating brittle and viscous behavior through the earthquake cycle in the Red River Shear Zone:Monitoring flips between reaction and textural softening and hardening.Tectonophysics.,587:46-62.
Xu X W,Wen X Z,Yu G H,et al.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 MW7.9Wenchuan earthquake,China.Geology,37(6):515-518.
Zhang L,He C R.2016.Frictional properties of phyllosilicate-rich mylonite and conditions for the brittle-ductile transition.Journal of Geophysical Research:Solid Earth,121(4):3017-3047.
Zhang P Z,Xu X W,Wen X Z,et al.2008.Slip rates and recurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May 12Wenchuan earthquake.Chinese Journal of Geophysics(in Chinese),51(4):1066-1073.
Zhang P Z,Wen X Z,Shen Z K,et al.2010.Oblique,high-angle,listric-reverse faulting and associated development of strain:The Wenchuan earthquake of 12 May 2008,Sichuan,China.Annual Review of Earth and Planetary Sciences,38(1):353-382.
Zhang P Z.2013a.Beware of slowly slipping faults.Nature Geoscience,6(5):323-324.
Zhang PZ.2013b.A review on active tectonics and deep crustal processes of the Western Sichuan region,eastern margin of the Tibetan Plateau.Tectonophysics,584:7-22.
Zhao G Z,Unsworth M J,Zhan Y,et al.2012.Crustal structure and rheology of the Longmenshan and Wenchuan MW7.9earthquake epicentral area from magnetotelluric data.Geology,40(12):1139-1142,doi:10.1130/G33703.1.
Zhou Y S,Jiang H K,He C R.2002.Experiments of brittle-plastic transition,modes of instability of Juyongguan granite at different T-P condition.Earthquake Research in China(in Chinese),18(4):389-400.
Zhou Y S,He C R.2009.The rheological structures of crust and mechanics of high-angle reverse fault slip for Wenchuan MS8.0earthquake.Chinese Journal of Geophysics(in Chinese),52(2):474-484.
Zhou Y S,Han L,Jing C,et al.2014.The rheological structures of brittle-plastic transition in Longmenshan fault zone and seismogenic mechanism of Wenchuan earthquake.Seismology and Geology(in Chinese),36(3):882-895.
Zhu S B,Zhang P Z.2010.Numeric Modeling of the Strain Accumulation and Release of the 2008 Wenchuan,Sichuan,China,Earthquake.Bulletin of the Seismological Society of America,100(5B):2825-2839.
Zhu S B,Zhang P Z.2013.FEM simulation of interseismic and coseismic deformation associated with the 2008 Wenchuan Earthquake.Tectonophysics,584:64-80.
陈九辉,刘启元,李顺成等.2009.汶川MS8.0地震余震序列重新定位及其地震构造研究.地球物理学报,52(2):390-397.
韩亮,周永胜,党嘉祥等.2009.3GPa熔融盐固体介质高温高压三轴压力容器的温度标定.高压物理学报,25(6):407-414.
韩亮,周永胜,姚文明.2013.中地壳断层带内微裂隙愈合与高压流体形成条件的模拟实验研究.地球物理学报,56(1):91-105,doi:10.6038/cjg20130110.
刘贵,周永胜,姚文明等.2013.组构对花岗片麻岩高温流变影响的实验研究.地球物理学报,56(7):2332-2347,doi:10.6038/cjg20130720.
刘照星,周永胜,刘贵等.2013.3GPa熔融盐固体介质三轴高温压力容器的轴压摩擦力标定.高压物理学报,27(1):19-28.
王绳祖,张流.1982.地壳温压条件下周口店花岗闪长岩的变形破坏.地震地质,4(4):68-91.
王绳祖,张流.1984.剪切破裂与粘滑-浅源强震发震机制的研究.地震地质,6(2):63-73.
王威,王绳祖,崔效峰.1989.地壳温压条件下居庸关花岗岩、济南辉长岩的强度特征.现代地壳运动研究,(4):163-168.
张培震,徐锡伟,闻学泽等.2008.2008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,51(4):1066-1073.
周永胜,蒋海昆,何昌荣.2002.不同温压条件下居庸关花岗岩脆塑性转化与失稳型式的实验研究.中国地震,18(4):389-400.
周永胜,何昌荣.2009.汶川地震区的流变结构与发震高角度逆断层滑动的力学条件.地球物理学报,52(2):474-484.
周永胜,韩亮,靖晨等,2014.龙门山断层脆塑性转化带流变结构与汶川地震孕震机制,地震地质,36(3):882-895.
Chen J H,Froment B,Liu Q Y,et al.2010.Distribution of seismic wave speed changes associated with the 12 May 2008 MW7.9Wenchuan earthquake.Geophysical Research Letters,37(18):L18302,doi:10.1029/2010GL044582.
Dang J X,Zhou Y S,Rybacki E,et al.2017.An experimental study on the brittle-plastic transition during deformation of granite.Journal of Asian Earth Sciences,139:30-39,doi:10.1016/j.jseaes.2016.08.023.
Duan Q B,Yang X S,Ma S L,et al.2016.Fluid-rock interactions in seismic faults:Implications from the structures and mineralogical and geochemical compositions of drilling cores from the rupture of the 2008 Wenchuan earthquake,China.Tectonophysics,666:260-280.
Gerald J F D,Stünitz H.1993.Deformation of granitoids at low metamorphic grade.I:Reactions and grain size reduction.Tectonophysics,221(3-4):269-297.
Han L,Zhou Y S,Dang J X,et al.2009.Temperature calibration for 3Gpa molten salt medium triaxial pressure vessel.Chinese Journal of High Pressure Physics(in Chinese),25(6):407-414.
Han L,Zhou Y S,Yao W M.2013.A simulating experimental study on crack healing and the formation of high pore fluid pressure in faults of middle crust.Chinese Journal of Geophysics(in Chinese),56(1):91-105,doi:10.6038/cjg20130110.
Han L,Zhou Y S,He C R,et al.2016.Sublithostatic pore fluid pressure in the brittle-ductile transition zone of Mesozoic Yingxiu-Beichuan fault and its implication for the 2008 MW7.9Wenchuan earthquake.Journal of Asian Earth Sciences,117:107-118,doi:10.1016/j.jseaes.2015.12.009.
Liu G,Zhou Y S,Yao W M,et al.2013.Experimental study on the effect of pre-existing fabric to deformation of granitic gneiss under high temperature and pressure.Chinese Journal of Geophysics(in Chinese),56(7):2332-2347,doi:10.6038/cjg20130720.
Liu G,Zhou Y S,He C R,et al.2016.An experimental study of effect of pre-existing fabric on deformation of foliated mylonite at high temperature and pressure.Geological Journal,51(1):92-112,doi:10.1002/gj.2611.
Liu G,Zhou Y S,Shi Y L,et al.2017.Strength variation and deformational behavior in anisotropic granitic mylonites under high-temperature and-pressure conditions-an experimental study.Journal of Structural Geology,96:21-34.
Liu Q Y,Van Der Hilst R D,Li Y,et al.2014.Eastward expansion of the Tibetan Plateau by crustal flow and strain partitioning across faults.Nature Geoscience,7(5):361-365,doi:10.1038/NGEO2130.
Liu Z X,Zhou Y S,Liu G,et al.2013.Axial friction calibration for3Gpa molten salt medium triaxial pressure vessel under high pressure and high temperature.Chinese Journal of High Pressure Physics(in Chinese),27(1):19-28.
Liu-Zeng J,Zhang Z,Wen L,et al.2009.Co-seismic ruptures of the 12 May 2008,MS8.0 Wenchuan earthquake,Sichuan:East-west crustal shortening on oblique,parallel thrusts along the eastern edge of Tibet.Earth and Planetary Science Letters,286(3-4):355-370.
Pec M,Stünitz H,Heilbronner R,et al.2016.Semi-brittle flow of granitoid fault rocks in experiments.Journal of Geophysical Research:Solid Earth,121(3):1677-1705.
Trepmann C A,St9ckhert B.2003.Quartz microstructures developed during non-steady state plastic flow at rapidly decaying stress and strain rate.Journal of Structural Geology,2003,25(12):2035-2051.
Wang S Z,Zhang L.1982.Deformation and failure of Zhoukoudian granodiorite at the crustal temperature and pressure.Seismology and Geology(in Chinese),4(4):68-91.
Wang S Z,Zhang L.1984.Shear fracture and stick-slip-a study on shock-generation mechanism of strong shallow earthquakes.Seismology and Geology(in Chinese),6(2):63-73.
Wang W,Wang S Z,Cui X F.1989.Strengh Characteristics of Juyongguan granite and Jinan gabbro at geologic crustal conditions.Modern Crustal Movement Research(in Chinese),(4):163-168.
Wintsch R P,Yeh M W.2013.Oscillating brittle and viscous behavior through the earthquake cycle in the Red River Shear Zone:Monitoring flips between reaction and textural softening and hardening.Tectonophysics.,587:46-62.
Xu X W,Wen X Z,Yu G H,et al.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 MW7.9Wenchuan earthquake,China.Geology,37(6):515-518.
Zhang L,He C R.2016.Frictional properties of phyllosilicate-rich mylonite and conditions for the brittle-ductile transition.Journal of Geophysical Research:Solid Earth,121(4):3017-3047.
Zhang P Z,Xu X W,Wen X Z,et al.2008.Slip rates and recurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May 12Wenchuan earthquake.Chinese Journal of Geophysics(in Chinese),51(4):1066-1073.
Zhang P Z,Wen X Z,Shen Z K,et al.2010.Oblique,high-angle,listric-reverse faulting and associated development of strain:The Wenchuan earthquake of 12 May 2008,Sichuan,China.Annual Review of Earth and Planetary Sciences,38(1):353-382.
Zhang P Z.2013a.Beware of slowly slipping faults.Nature Geoscience,6(5):323-324.
Zhang PZ.2013b.A review on active tectonics and deep crustal processes of the Western Sichuan region,eastern margin of the Tibetan Plateau.Tectonophysics,584:7-22.
Zhao G Z,Unsworth M J,Zhan Y,et al.2012.Crustal structure and rheology of the Longmenshan and Wenchuan MW7.9earthquake epicentral area from magnetotelluric data.Geology,40(12):1139-1142,doi:10.1130/G33703.1.
Zhou Y S,Jiang H K,He C R.2002.Experiments of brittle-plastic transition,modes of instability of Juyongguan granite at different T-P condition.Earthquake Research in China(in Chinese),18(4):389-400.
Zhou Y S,He C R.2009.The rheological structures of crust and mechanics of high-angle reverse fault slip for Wenchuan MS8.0earthquake.Chinese Journal of Geophysics(in Chinese),52(2):474-484.
Zhou Y S,Han L,Jing C,et al.2014.The rheological structures of brittle-plastic transition in Longmenshan fault zone and seismogenic mechanism of Wenchuan earthquake.Seismology and Geology(in Chinese),36(3):882-895.
Zhu S B,Zhang P Z.2010.Numeric Modeling of the Strain Accumulation and Release of the 2008 Wenchuan,Sichuan,China,Earthquake.Bulletin of the Seismological Society of America,100(5B):2825-2839.
Zhu S B,Zhang P Z.2013.FEM simulation of interseismic and coseismic deformation associated with the 2008 Wenchuan Earthquake.Tectonophysics,584:64-80.
陈九辉,刘启元,李顺成等.2009.汶川MS8.0地震余震序列重新定位及其地震构造研究.地球物理学报,52(2):390-397.
韩亮,周永胜,党嘉祥等.2009.3GPa熔融盐固体介质高温高压三轴压力容器的温度标定.高压物理学报,25(6):407-414.
韩亮,周永胜,姚文明.2013.中地壳断层带内微裂隙愈合与高压流体形成条件的模拟实验研究.地球物理学报,56(1):91-105,doi:10.6038/cjg20130110.
刘贵,周永胜,姚文明等.2013.组构对花岗片麻岩高温流变影响的实验研究.地球物理学报,56(7):2332-2347,doi:10.6038/cjg20130720.
刘照星,周永胜,刘贵等.2013.3GPa熔融盐固体介质三轴高温压力容器的轴压摩擦力标定.高压物理学报,27(1):19-28.
王绳祖,张流.1982.地壳温压条件下周口店花岗闪长岩的变形破坏.地震地质,4(4):68-91.
王绳祖,张流.1984.剪切破裂与粘滑-浅源强震发震机制的研究.地震地质,6(2):63-73.
王威,王绳祖,崔效峰.1989.地壳温压条件下居庸关花岗岩、济南辉长岩的强度特征.现代地壳运动研究,(4):163-168.
张培震,徐锡伟,闻学泽等.2008.2008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,51(4):1066-1073.
周永胜,蒋海昆,何昌荣.2002.不同温压条件下居庸关花岗岩脆塑性转化与失稳型式的实验研究.中国地震,18(4):389-400.
周永胜,何昌荣.2009.汶川地震区的流变结构与发震高角度逆断层滑动的力学条件.地球物理学报,52(2):474-484.
周永胜,韩亮,靖晨等,2014.龙门山断层脆塑性转化带流变结构与汶川地震孕震机制,地震地质,36(3):882-895.