断层黏滑动态变形过程的实验研究
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摘要
实验研究断层黏滑过程的变形演化,尤其是失稳黏滑瞬间的断层位移演化特征,对于了解地震从孕育到发生的全过程具有重要意义.本文基于数字散斑相关方法(digital speckle correlation method,DSCM),用三套图像采集系统(两套低速和一套高速图像采集系统)搭建了断层黏滑过程的多观测区域、多时间尺度的变形场测量系统,并用此系统对一种花岗岩双剪滑动模型的黏滑过程进行了实验研究.对间黏滑期和黏滑期断层位移演化特征进行深入分析的结果表明:间黏滑期断层位移演化体现出空间上的非均匀性和时间上的"趋同化"特征,断层滑动趋同化也许是断层错动匀阻化的一种宏观表现形式;断层黏滑动态过程持续时间非常短(本文300mm断层黏滑过程持续时间约在1ms量级),黏滑失稳前会出现预滑,预滑出现到黏滑失稳发生所经历的时间与黏滑失稳过程所用时间相差一个量级;断层的一次黏滑由若干个滑动速度不同的、小的失稳滑动组成,黏滑失稳过程中断层的滑动速度呈现出波动性,整个滑动过程中断层经历了多个高速滑动和低速滑动的交错.
Observation of the deformation evolution of a stick-slipping fault,especially the dynamic fault displacement evolution characteristics during the very short period of unstable stick-slip,is of great importance to the understanding of initialization and occurrence of earthquakes.Based on the digital speckle correlation method(DSCM),a deformation observation system with multi measurement areas and multi data acquisition speeds is constructed by combining 3 different(2 low speed and 1 high speed) CCD cameras.The stick-slip of a double-shearing slipping rock specimen made of Fangshan granodiorite is experimentally studied,and the fault displacements in the locked stage and the unstable slipping stage are measured using DSCM.The experimental results show that the fault displacements on different locations are different and spatially heterogeneous in the locked stage,however the displacements tend to be uniform at the end of the stage.The uniformization of the fault displacements could probably be considered as a macro form of expression of the uniformization of fault friction resistance.The dynamic displacement results show that the duration of the unstable stick-slip of the fault is very short(about 1 ms for the 300 mm long fault in the experiment in this paper).Pre-slip,i.e.,an obvious acceleration of the slipping speed just before the unstable slip is found in the experiment.The duration of the pre-slip is about one order of magnitude longer than that of the stick-slip.The slipping speed of the fault varies during the stick-slip.The whole stick-slip is composed of several unstable slips with different slipping speeds.
Observation of the deformation evolution of a stick-slipping fault,especially the dynamic fault displacement evolution characteristics during the very short period of unstable stick-slip,is of great importance to the understanding of initialization and occurrence of earthquakes.Based on the digital speckle correlation method(DSCM),a deformation observation system with multi measurement areas and multi data acquisition speeds is constructed by combining 3 different(2 low speed and 1 high speed) CCD cameras.The stick-slip of a double-shearing slipping rock specimen made of Fangshan granodiorite is experimentally studied,and the fault displacements in the locked stage and the unstable slipping stage are measured using DSCM.The experimental results show that the fault displacements on different locations are different and spatially heterogeneous in the locked stage,however the displacements tend to be uniform at the end of the stage.The uniformization of the fault displacements could probably be considered as a macro form of expression of the uniformization of fault friction resistance.The dynamic displacement results show that the duration of the unstable stick-slip of the fault is very short(about 1 ms for the 300 mm long fault in the experiment in this paper).Pre-slip,i.e.,an obvious acceleration of the slipping speed just before the unstable slip is found in the experiment.The duration of the pre-slip is about one order of magnitude longer than that of the stick-slip.The slipping speed of the fault varies during the stick-slip.The whole stick-slip is composed of several unstable slips with different slipping speeds.
引文
[1]Brace W F,Byerlee J D.Stick-slip as a mechanism forearthquakes.Science,1966,153(3739):990-992.
[2]Seholz C H,Molnar P,Johnson T.Detailed studies offrictional sliding of granite and implications for the earthquakemechanism.J.Geophys.Res.,1972,77(32):6392-6406.
[3]施行觉,王其允.粘滑位移的直接测量和剪切破裂能的修正.地震学报,1989,11(2):153-160.Shi X J,Wang Q R.Direct measurement of displacement andestimate of shear fracture energy.Acta Seismologica Sinica(in Chinese),1989,11(2):153-160.
[4]Okubo P G,Diterich J H.Fracture energy of stick-slipevents in a large scale biaxial experiment.Geophys.Res.Lett.,1981,8(8):887-890.
[5]马文涛,马瑾,刘力强等.雁列断层变形过程中的声发射特征.地震地质,1995,17(4):342-348.Ma W T,Ma J,Liu L Q,et al.The characteristics ofacoustic emission in en echelon structure.Seismology andGeology(in Chinese),1995,17(4):342-348.
[6]刘力强,马胜利,马瑾等.岩石构造对声发射统计特征的影响.地震地质,1999,21(4):377-386.Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistic characteristics of acoustic emission.Seismology andGeology(in Chinese),1999,21(4):377-386.
[7]蒋海昆,马胜利,张流等.含障碍体平直断层标本变形过程中群体微破裂事件的时空演化特征.地球物理学报,2003,46(2):209-216.Jiang H K,Ma S L,Zhang L,et al.Spatial-temporalcharacteristics of acoustic emission of rock sample withregular fault and a columnar barrier during deformation.Chinese J.Geophys.(in Chinese),2003,46(2):209-216.
[8]马瑾,马胜利,刘力强等.断层几何结构与物理场的演化及失稳特征.地震学报,1996,18(2):200-205.Ma J,Ma S L,Liu L Q,et al.The evolution of physicalfields and instability characteristics in relation with Faultgeometry structure.Acta Seismologica Sinica(in Chinese),1996,18(2):200-205.
[9]马胜利,马瑾,刘力强.典型构造变形过程中物理场时空演化的实验和理论研究.地震,1995,(S1):55-65.Ma S L,Ma J,Liu L Q.Theoretical and experimentalstudies on spatial-temporal evolution of physical field duringdeformation of fault system with typical geometric textures.Earthquake(in Chinese),1995,(S1):55-65.
[10]刘力强,马瑾,马胜利.典型构造背景应变场特征及其演化趋势.地震地质,1995,17(4):349-356.Liu L Q,Ma J,Ma S L.Characteristics and evolution ofbackground strain field on typical structure models.Seismologyand Geology(in Chinese),1995,17(4):349-356.
[11]邓志辉,马胜利,马瑾等.粘滑失稳及其物理场时空分布的实验研究.地震地质,1995,17(4):305-310.Deng Z H,Ma S L,Ma J,et al.Experimental study onstick-slip instability and evolution of its physical fields.Seismology and Geology(in Chinese),1995,17(4):305-310.
[12]Kato N,Satoh T,Lei X L,et al.Effect of fault bend on therupture propagation process of stick-slip.Tectonophysics,1999,310(1-4):81-99.
[13]Sutton M A.Digital Image Correlation for Shape andDeformation Measurements.Springer Handbook of ExperimentalSolid Mechanics,2008:565-598.
[14]陈俊达,马少鹏,刘善军等.应用数字散斑相关方法实验研究雁列断层变形破坏过程.地球物理学报,2005,48(6):1350-1356.Chen J D,Ma S P,Liu S J,et al.An experimental study ofthe failure process of en-echelon fault structure using thedigital speckle correlation method.Chinese J.Geophys.(inChinese),2005,48(6):1350-1356.
[15]王绳祖,施良骐.岩石错动面的凹凸不平及两种突发失稳.地震地质,1985,7(3):73～80.Wang S Z,Shi L Q.Asperity of sliding zone and twodifferent kinds of sudden instabilities in rocks.Seismologyand Geology(in Chinese),1985,7(3):73-80.
[16]李建国,王绳祖.岩石错动面的非匀阻性与突发失稳.地震地质,1992,14(1):79-88.Li J G,Wang S Z.Resistance nonuniformity and suddeninstability of sliding zone in rocks.Seismology and Geology(in Chinese),1992,14(1):79-88.
[2]Seholz C H,Molnar P,Johnson T.Detailed studies offrictional sliding of granite and implications for the earthquakemechanism.J.Geophys.Res.,1972,77(32):6392-6406.
[3]施行觉,王其允.粘滑位移的直接测量和剪切破裂能的修正.地震学报,1989,11(2):153-160.Shi X J,Wang Q R.Direct measurement of displacement andestimate of shear fracture energy.Acta Seismologica Sinica(in Chinese),1989,11(2):153-160.
[4]Okubo P G,Diterich J H.Fracture energy of stick-slipevents in a large scale biaxial experiment.Geophys.Res.Lett.,1981,8(8):887-890.
[5]马文涛,马瑾,刘力强等.雁列断层变形过程中的声发射特征.地震地质,1995,17(4):342-348.Ma W T,Ma J,Liu L Q,et al.The characteristics ofacoustic emission in en echelon structure.Seismology andGeology(in Chinese),1995,17(4):342-348.
[6]刘力强,马胜利,马瑾等.岩石构造对声发射统计特征的影响.地震地质,1999,21(4):377-386.Liu L Q,Ma S L,Ma J,et al.Effect of rock structure onstatistic characteristics of acoustic emission.Seismology andGeology(in Chinese),1999,21(4):377-386.
[7]蒋海昆,马胜利,张流等.含障碍体平直断层标本变形过程中群体微破裂事件的时空演化特征.地球物理学报,2003,46(2):209-216.Jiang H K,Ma S L,Zhang L,et al.Spatial-temporalcharacteristics of acoustic emission of rock sample withregular fault and a columnar barrier during deformation.Chinese J.Geophys.(in Chinese),2003,46(2):209-216.
[8]马瑾,马胜利,刘力强等.断层几何结构与物理场的演化及失稳特征.地震学报,1996,18(2):200-205.Ma J,Ma S L,Liu L Q,et al.The evolution of physicalfields and instability characteristics in relation with Faultgeometry structure.Acta Seismologica Sinica(in Chinese),1996,18(2):200-205.
[9]马胜利,马瑾,刘力强.典型构造变形过程中物理场时空演化的实验和理论研究.地震,1995,(S1):55-65.Ma S L,Ma J,Liu L Q.Theoretical and experimentalstudies on spatial-temporal evolution of physical field duringdeformation of fault system with typical geometric textures.Earthquake(in Chinese),1995,(S1):55-65.
[10]刘力强,马瑾,马胜利.典型构造背景应变场特征及其演化趋势.地震地质,1995,17(4):349-356.Liu L Q,Ma J,Ma S L.Characteristics and evolution ofbackground strain field on typical structure models.Seismologyand Geology(in Chinese),1995,17(4):349-356.
[11]邓志辉,马胜利,马瑾等.粘滑失稳及其物理场时空分布的实验研究.地震地质,1995,17(4):305-310.Deng Z H,Ma S L,Ma J,et al.Experimental study onstick-slip instability and evolution of its physical fields.Seismology and Geology(in Chinese),1995,17(4):305-310.
[12]Kato N,Satoh T,Lei X L,et al.Effect of fault bend on therupture propagation process of stick-slip.Tectonophysics,1999,310(1-4):81-99.
[13]Sutton M A.Digital Image Correlation for Shape andDeformation Measurements.Springer Handbook of ExperimentalSolid Mechanics,2008:565-598.
[14]陈俊达,马少鹏,刘善军等.应用数字散斑相关方法实验研究雁列断层变形破坏过程.地球物理学报,2005,48(6):1350-1356.Chen J D,Ma S P,Liu S J,et al.An experimental study ofthe failure process of en-echelon fault structure using thedigital speckle correlation method.Chinese J.Geophys.(inChinese),2005,48(6):1350-1356.
[15]王绳祖,施良骐.岩石错动面的凹凸不平及两种突发失稳.地震地质,1985,7(3):73～80.Wang S Z,Shi L Q.Asperity of sliding zone and twodifferent kinds of sudden instabilities in rocks.Seismologyand Geology(in Chinese),1985,7(3):73-80.
[16]李建国,王绳祖.岩石错动面的非匀阻性与突发失稳.地震地质,1992,14(1):79-88.Li J G,Wang S Z.Resistance nonuniformity and suddeninstability of sliding zone in rocks.Seismology and Geology(in Chinese),1992,14(1):79-88.
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