硬石膏断层带摩擦稳定性转换与微破裂特征的实验研究
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摘要
断层带摩擦稳定性转换及其对应的微破裂特征对于地震成核条件和慢地震机理研究具有重要的意义.本文利用双轴实验装置研究了硬石膏断层带摩擦稳定性的转换及其对应的应变变化、微破裂特征,并分析了实验标本的微观结构.实验结果表明,σ_2和加载点速度对断层滑动稳定性具有显著影响.在低σ_2条件下,硬石膏断层带出现不稳定滑动,变形以局部化的脆性破裂和摩擦为主;随σ_2的增加,断层由不稳定滑动向稳定滑动转换,断层带变形方式逐渐转变为分布式的破裂.在低σ_2条件下,硬石膏断层带在较低加载点速度下表现为速度强化且滑动稳定,在中等加载点速度下表现为速度弱化并伴有准周期性的黏滑,在较高加载点速度下又有转向速度强化的趋势,σ_2的提高使得速度弱化的范围逐渐减少,滑动趋于稳定.上述两次转换对应不同的微破裂特征,在较高速度下从速度弱化转换为速度强化时,断层滑动伴有能量较小但频度很高的微破裂活动,而在较低速度下从速度弱化转换为速度强化时,断层滑动伴有间歇性的微破裂,这与断层带的微观结构特征有较好的对应关系,表明其转换机制是不同的.
Study on frictional stability transition of the fault zone and the corresponding micro-fracturing characteristics has great significance for understanding earthquake nucleation condition and mechanism of slow earthquakes. In this paper, using biaxial experimental apparatus, we studied the frictional stability transition of the anhydrite fault zones and the corresponding change in strain and micro-fracturing characteristics, and analyzed microstructure of the fault zones after experiments. The results show that σ_2 and loading point velocity have a significant impact on the stability of fault sliding. At low σ_2, anhydrite fault zone behaves as unstable frictional sliding, and the deformation is predominated by localized brittle fracturing and frictional sliding. As the σ_2 increases, transition from unstable sliding to stable sliding of the fault zone occurs, and the deformation style gradually transforms to distributed fracturing. Anhydrite fault zone shows velocity strengthening and stable sliding at lower loading point velocities, and velocity weakening accompanied by quasi-periodic stick-slip at moderate velocities. At higher velocities, frictional sliding tends to turn into velocity strengthening again. With increasing of σ_2, the scope of velocity weakening gradually decreases and frictional sliding becomes stable. Moreover, the micro-fracturing characteristics corresponding to the two transitions are different. At higher velocities, fault sliding is accompanied by micro-fracturing activity with small energy but high frequency when friction transforms from velocity weakening to velocity strengthening. While at lower velocities, fault sliding is accompanied by episodic micro-fracturing when friction transforms from velocity weakening to velocity strengthening. This coincides with the characteristics of the microstructure of fault zones, indicating that the mechanism of the two transitions is different.
Study on frictional stability transition of the fault zone and the corresponding micro-fracturing characteristics has great significance for understanding earthquake nucleation condition and mechanism of slow earthquakes. In this paper, using biaxial experimental apparatus, we studied the frictional stability transition of the anhydrite fault zones and the corresponding change in strain and micro-fracturing characteristics, and analyzed microstructure of the fault zones after experiments. The results show that σ_2 and loading point velocity have a significant impact on the stability of fault sliding. At low σ_2, anhydrite fault zone behaves as unstable frictional sliding, and the deformation is predominated by localized brittle fracturing and frictional sliding. As the σ_2 increases, transition from unstable sliding to stable sliding of the fault zone occurs, and the deformation style gradually transforms to distributed fracturing. Anhydrite fault zone shows velocity strengthening and stable sliding at lower loading point velocities, and velocity weakening accompanied by quasi-periodic stick-slip at moderate velocities. At higher velocities, frictional sliding tends to turn into velocity strengthening again. With increasing of σ_2, the scope of velocity weakening gradually decreases and frictional sliding becomes stable. Moreover, the micro-fracturing characteristics corresponding to the two transitions are different. At higher velocities, fault sliding is accompanied by micro-fracturing activity with small energy but high frequency when friction transforms from velocity weakening to velocity strengthening. While at lower velocities, fault sliding is accompanied by episodic micro-fracturing when friction transforms from velocity weakening to velocity strengthening. This coincides with the characteristics of the microstructure of fault zones, indicating that the mechanism of the two transitions is different.
引文
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[4] Ruina A L.Slip instability and state variable friction.J.Geophys.Res.,1983,88:10359～10370
[5] Dragert H,Wang K,James T S.A silent slip event on the deeper Cascadia subduction interface.Science,2001,292:1525～1528
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[7] Obara K.NonvoIcanic deep tremor associated with subduction in southwest Japan.Science,2002,296(557:3) :1679～1681
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[11] Shibazaki B,Lio Y.On the physical mechanism of silent slip events along the deeper part of the seismogenic zone.Geophy.Res.Lett.,2003,30,9,1489,doi:10． 1029/2003GL01747
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[14] Ma J,Ma S L.The role of fault material in fault movement and seismological significance.Earthquakee Research in China,1987,1,3,361～376
[15] Shimamoto T.Transition Between Frictional Slip and Ductile Flow for Halite Shear Zones at Room Temperature.Science,1986,231:711～714
[16] Blanpied M L,Lockner D A,Byerlee J D.Frictional slip of granite at hydrotherrnaI conditions.J.Geophys.Res.,1995,100(B7) :13045～13064
[17] He C,Yao W,Wang Z,et al.Strength and stability of frictional sliding of gabbro gouge at elevated temperatures.Tectonophysics,2006,427:217～229
[18] He C,Wang Z,Yao W.Frictional sliding of gabbro gouge under hydrothermal conditions.Tectonophysics,2007,445:353～362
[19] Bos B,Spiers C J.Frictional-viscous flow of phyllosilicate-bearing fault rock.microphysical nodel and implications for crustal strength profiles.J.Geophys.Res.,2002,107,B2,10． 1029/2001JB900301
[20] Niemeijer A R,Spiers C J.Velocity dependence of strength and healing behaviour in simulated phyllosilicate bearing fault gouge.Tectonophysics,2006,427:231～253
[21] 蒋海昆,马胜利,周焕鹏等.双向压缩条件下非均匀断层标本变形过程中的声发射活动特征.地震学报,2006,28(3) :295～304 Jiang H K,Ma S L,Zhou H P,et al.Spatial and temporal characteristic of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression.Earthquake Journal,2006,28(3) :295～304
[22] 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 on statistic characteristics of acoustic emission.Seismology and Geology(in Chinese),1999,21(4) :377～386
[23] Bartlett W L,Friedman M,Logan J M.Experimental folding and faulting of rocks under confining pressure.Tectonophysics,1981,79:255～277
[24] Marone C,Scholz C H.Particle-size distribution and microstructures within simulated fault gouge.J.Structural Geology,1989,11(7) :799～814
[25] Marone C,Raleigh C B,Scholz C H.Frictional behavior and constitutive modeling of simulated fault gouge.J.Geophys.Res.,1990,95(B5) :7007～7025．
[26] Holdsworth R E.Weak faults-Rotten cores.Science,2004,303:181～182
[27] 李广信.高等土力学.清华大学出版社,2005 Li G X.Advanced Soil Mechanics(in Chinese),Beijing:Tsinghua University Press,2005
[2] Scholz C H.The brittle-plastic transition and the depth of seismic faulting.Geologisthe Rundschau,1988,77,1:319～328
[3] Dieterich J H.Modelling of rock friction:1． Experimental results and constitutive equations.J.Geophys.Res.,1979,84:2161～2168
[4] Ruina A L.Slip instability and state variable friction.J.Geophys.Res.,1983,88:10359～10370
[5] Dragert H,Wang K,James T S.A silent slip event on the deeper Cascadia subduction interface.Science,2001,292:1525～1528
[6] Miller M M,Melbourne T,Johnson D J,et al.Periodic slow earthquakes from the Cascadia subduction zone.Science,2002,295:2423
[7] Obara K.NonvoIcanic deep tremor associated with subduction in southwest Japan.Science,2002,296(557:3) :1679～1681
[8] Ozawa S,Murakami M,et al.Detection and monitoring of ongoing aseismic slip in the Tokai region,central Japan.Science,2002,298:1009～1012
[9] Lowry A R,Larson K M,Kostoglodov V,et al.Transient fault slip in Guerrero,southern Mexico.Geophys.Res.Lett.,2001,28(19) :3753～3756
[10] Kostoglodov V,Singh S K,Santiago J A,et al.A large silent earthquake in the Guerrero seismic gap,Mexico.Geophys.Res.Lett.,2003,30(15) ,1807,doi:10． 1029/2003GL017219
[11] Shibazaki B,Lio Y.On the physical mechanism of silent slip events along the deeper part of the seismogenic zone.Geophy.Res.Lett.,2003,30,9,1489,doi:10． 1029/2003GL01747
[12] Liu Y-j,Rice J R.Aseismic slip transients emerge spontaneously in three-dimensional rate and state modeling of subduction earthquakes sequences.J.Geophys.Res.,2005,110,Bo8307,doi:10． 1029/2004JB003424
[13] Stesky R.Mechanisms of high temperature frictional sliding in Westerly granite.Can.J.Earth Sci.,1978,155:361～375
[14] Ma J,Ma S L.The role of fault material in fault movement and seismological significance.Earthquakee Research in China,1987,1,3,361～376
[15] Shimamoto T.Transition Between Frictional Slip and Ductile Flow for Halite Shear Zones at Room Temperature.Science,1986,231:711～714
[16] Blanpied M L,Lockner D A,Byerlee J D.Frictional slip of granite at hydrotherrnaI conditions.J.Geophys.Res.,1995,100(B7) :13045～13064
[17] He C,Yao W,Wang Z,et al.Strength and stability of frictional sliding of gabbro gouge at elevated temperatures.Tectonophysics,2006,427:217～229
[18] He C,Wang Z,Yao W.Frictional sliding of gabbro gouge under hydrothermal conditions.Tectonophysics,2007,445:353～362
[19] Bos B,Spiers C J.Frictional-viscous flow of phyllosilicate-bearing fault rock.microphysical nodel and implications for crustal strength profiles.J.Geophys.Res.,2002,107,B2,10． 1029/2001JB900301
[20] Niemeijer A R,Spiers C J.Velocity dependence of strength and healing behaviour in simulated phyllosilicate bearing fault gouge.Tectonophysics,2006,427:231～253
[21] 蒋海昆,马胜利,周焕鹏等.双向压缩条件下非均匀断层标本变形过程中的声发射活动特征.地震学报,2006,28(3) :295～304 Jiang H K,Ma S L,Zhou H P,et al.Spatial and temporal characteristic of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression.Earthquake Journal,2006,28(3) :295～304
[22] 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 on statistic characteristics of acoustic emission.Seismology and Geology(in Chinese),1999,21(4) :377～386
[23] Bartlett W L,Friedman M,Logan J M.Experimental folding and faulting of rocks under confining pressure.Tectonophysics,1981,79:255～277
[24] Marone C,Scholz C H.Particle-size distribution and microstructures within simulated fault gouge.J.Structural Geology,1989,11(7) :799～814
[25] Marone C,Raleigh C B,Scholz C H.Frictional behavior and constitutive modeling of simulated fault gouge.J.Geophys.Res.,1990,95(B5) :7007～7025．
[26] Holdsworth R E.Weak faults-Rotten cores.Science,2004,303:181～182
[27] 李广信.高等土力学.清华大学出版社,2005 Li G X.Advanced Soil Mechanics(in Chinese),Beijing:Tsinghua University Press,2005
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