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1.
Energy partitioning during seismic slip in pseudotachylyte-bearing faults (Gole Larghe Fault, Adamello, Italy) 总被引：1，自引：0，他引：1
Lidia Pittarello Giulio Di Toro Andrea Bizzarri Giorgio Pennacchioni Jafar Hadizadeh Massimo Cocco 《Earth and Planetary Science Letters》2008,269(1-2):131-139
The determination of the earthquake energy budget remains a challenging issue for Earth scientists, as understanding the partitioning of energy is a key towards the understanding the physics of earthquakes. Here we estimate the partition of the mechanical work density into heat and surface energy (energy required to create new fracture surface) during seismic slip on a location along a fault. Earthquake energy partitioning is determined from field and microstructural analyses of a fault segment decorated by pseudotachylyte (solidified friction-induced melt produced during seismic slip) exhumed from a depth of ~ 10 km—typical for earthquake hypocenters in the continental crust. Frictional heat per unit fault area estimated from the thickness of pseudotachylytes is ~ 27 MJ m− 2. Surface energy, estimated from microcrack density inside clast (i.e., cracked grains) entrapped in the pseudotachylyte and in the fault wall rock, ranges between 0.10 and 0.85 MJ m− 2. Our estimates for the studied fault segment suggest that ~ 97–99% of the energy was dissipated as heat during seismic slip. We conclude that at 10 km depth, less than 3% of the total mechanical work density is adsorbed as surface energy on the fault plane during earthquake rupture. 相似文献
2.
G. G. Kocharyan A. A. Ostapchuk V. K. Markov D. V. Pavlov 《Izvestiya Physics of the Solid Earth》2014,50(3):355-366
We present the results of laboratory experiments on studying the formation of different slip modes on the interfaces in a rock massif such as aseismic creep, stick-slip, and periodic slow-slip events. It is shown that the way of releasing the accumulated elastic energy is determined by the mesoscale structure of the gouge rather than by its macroscopic strength characteristics. The evolution of the stress chains which are formed and broken during the displacement on the fracture, as well as the length and number of these chains, completely determines the regularities of the deformation. The role of these load-bearing elements in nature can be played, e.g., by the “contact spots,” which determine the regularities of stress concentration near the interblock boundary. We consider the effects of low-amplitude vibrations on stressed fractures. It is shown that, depending on the mode of deformation, the vibration impact can either reduce or boost the amplitude of separate events and the fraction of energy that is released dynamically. In the conclusion of the paper, we discuss the possibility of using the shear strength of the fault zone as a geomechanical parameter controlling the mode of deformation. 相似文献
3.
Abstract The seismic slip that occurred during the 1999 Chi-Chi earthquake in Taiwan showed contrastive behaviors in different regions along the Chelungpu Fault: A large and smooth slip occurred in the north, while a relatively small slip associated with high-frequency seismic wave radiation occurred in the south. The core samples from shallow boreholes at northern (Fengyuan) and southern (Nantou) sites penetrating the seismic Chelungpu Fault were analyzed. The fault zones at the northern site are characterized by soft clayey material associated with clayey injection veins. This suggests that the fault zones were pressurized during ancient seismic slip events, and hence the elastohydrodynamic lubrication occurred effectively. In contrast, the fault rock from the southern site is old pseudotachylyte that has been shattered by repeated ancient seismic slip events. Statistical analysis of many pseudotachylyte fragments reveals that the degree of frictional melting tended to be low. In this case, the seismic slip is restrained by the mechanical barrier of a highly viscous melt layer. These contrastive fault rocks were produced by repeated ancient seismic slip events, but the two corresponding mechanisms of friction are likely to have also occurred during the 1999 Chi-Chi earthquake, thus causing the contrastive slip behaviors in the north and south. 相似文献
4.
简述了最近20年来国内外岩石高速摩擦实验研究领域的进展和动态:岩石高速摩擦实验技术的发展实现了对高滑动速率、大位移的地震过程的实验模拟;其结果揭示了岩石和断层泥在地震滑动速率下的力学性状,深化了对断层滑动弱化机制、临界滑动距离、以及地震发生过程的认识和理解;实验在假玄武玻璃成因方面取得了重要进展,并提出了断层发生地震滑动可能留下的其它地质证据,可望为研究断层滑动性状与地震物理过程提供新的思路和信息.岩石高速摩擦实验今后的发展方向主要包括:发展具有加温系统和孔隙压系统的岩石高速摩擦实验装置,研究水热作用下岩石和断层泥的高速摩擦性状;室内实验和地震资料分析相结合研究断层滑动和地震机制;室内实验和野外地质调查相结合探索断层发生地震错动的地质证据等等. 相似文献
5.
Abstract The 1999 Chi-Chi earthquake in Taiwan ( M w = 7.6) produced a surface rupture along the north–south-striking Chelungpu thrust fault with pure dip-slip (east side up) and left lateral strike-slip displacements. Near-field strong-motion data for the northern part of the fault illustrate a distinct lack of the high-frequency seismic radiation associated with a large slip (10–15 m) and a rapid slip velocity (2–4 m/s), suggesting a smooth seismic slip associated with low dynamic frictional resistance on the fault. A drillhole was constructed at shallow depths in the possible fault zones of the northern part of the Chelungpu Fault, which may have slipped during the 1999 earthquake. One of the zones consists of a 20-cm-thick, unconsolidated fault breccia with a chaotic texture lacking both discrete slip surfaces (e.g. Riedel shears) and grain crushing. Other possible fault zones are marked by the narrow (less than a few centimeters) gouge zone in which clayey material intrudes into the damaged zone outside of the gouge zone. These characteristic fault rock textures suggest that the slip mechanisms at shallow levels during the earthquake involved either granular flow of initially unconsolidated material or slip localization under elevated pore pressure along the narrow clayey gouge zone. Because both mechanisms lead to low dynamic frictional resistance on the fault, the rapid seismic slip in the deep portions of the fault (i.e. the source region of strong-motion radiation) could have been accommodated by frictionless slip on the shallow portions of the fault. The combination of strong-motion data and fault rock analysis suggests that smooth slip associated with low dynamic friction occurred on both the deep and shallow portions of the fault, resulting in a large slip between the source region and the surface in the northern region. 相似文献
6.
利用1999—2007期和2009—2013期中国大陆GPS速度场数据,采用DEFNODE负位错反演程序估算了川滇菱形块体东边界——鲜水河—安宁河—则木河—小江断裂带在汶川地震前后的断层闭锁程度和滑动亏损空间分布动态变化特征,讨论了汶川地震对该断裂系统的影响范围和程度,并结合b值空间分布和地震破裂时-空结果分析了断裂系统的强震危险段.结果表明,汶川地震前鲜水河断裂最南端为完全闭锁(闭锁深度25km),中南段地表以下10~15km深度为强闭锁状态,中北段基本处于蠕滑状态;安宁河断裂最南端闭锁很弱,其余位置闭锁深度为10~15km;则木河断裂除最南端闭锁较弱以外,其余位置基本为完全闭锁;小江断裂在巧家以南、东川以南、宜良附近、华宁以北等四处位置闭锁较弱,其余位置为强闭锁.10年尺度的GPS速度场反演所得断层闭锁程度所指示的强震危险段,主要为鲜水河断裂道孚—八美段、安宁河断裂中段、则木河断裂中北段、小江断裂北段东川附近、小江断裂南段华宁—建水段,该结果与地质尺度的断层地震空区和30年尺度的b值空间分布所指示的危险段落具有一致性.汶川地震后断裂带远、近场速度分布和块体运动状态发生变化,这种区域地壳运动调整使得负位错模型反演得到的断裂带闭锁情况发生一定变化.汶川地震前后川滇菱形块体东边界平行断层滑动亏损速率均为左旋走滑亏损,且在安宁河断裂北端、则木河断裂中北段滑动亏损速率最大;除鲜水河断裂中南段与最南端和小江断裂东川附近以外,其余断裂震后滑动亏损速率均有所增加.垂直断层滑动亏损速率既有拉张亏损也有挤压亏损,且鲜水河断裂最南端由震前挤压转变为震后拉张,其余断裂除了安宁河断裂和小江断裂中段与最北端存在挤压滑动亏损速率外均为拉张速率. 相似文献
7.
综合利用1999—2013年中国大陆构造环境监测网络GPS速度场与跨六盘山断裂布设的10个GPS连续站观测剖面, 基于块体-位错模型, 研究了六盘山断裂震间闭锁性质与滑动亏损的空间分布。 结果显示, 六盘山断裂震间闭锁具有明显的分段特征, 其中断裂南段的闭锁程度最强, 滑动亏损速率的平均值最大, 地震危险性最高; 断裂北段闭锁程度弱于南段, 但断层浅部的滑动亏损速率平均值最大, 应变积累速度快, 也具有一定的发震能力; 中段闭锁程度最弱, 滑动亏损速率最小, 发震可能性小于南段和北段。 相似文献
8.
G. G. Kocharyan A. A. Ostapchuk D. V. Pavlov A. M. Budkov 《Izvestiya Physics of the Solid Earth》2018,54(6):914-925
The results of laboratory experiments aimed at studying the pattern of the transition process of a model fault into a metastable state are presented. The experiments are conducted on a slider model installed onto a long granite base wherein vibrations are excited. The idea of the experiments is that the mechanical properties of the fault change under the transition into the metastable state. These changes can be detected by the detailed examination of the parameters of microseismic noise. The conducted experiments show that, despite the low Q-factor of the block–fault mechanical system, the spectrum of the recorded oscillations definitely contains the harmonic components corresponding to the eigenmodes of this system. In the model with the interblock contact filled with quartz sand, the fundamental mode of the free oscillations alters most noticeably in the frequency band 1000–1200 Hz, where the clear effect of the spectral peak’s migration towards lower frequencies is observed as the contact approaches the moment of dynamic failure, and the approximately initial value is recovered after the sliding stops. The revealed effect gives hope that the changes in the stress–strain state of the fault zone at the final stage of earthquake preparation can be detected by analyzing the parameters of low-frequency seismic noise. The segment of the record during and after the passage of surface waves from remote earthquakes is perhaps amongst the most favorable for determining the characteristic values of the region under study. These oscillations with a period of a few dozen seconds have significant amplitudes and durations, which promotes the excitation of the resonant vibrations of the blocks. 相似文献
9.
利用1999—2007期GPS水平速度场数据,采用Defnode负位错反演程序估算了龙门山断裂在汶川地震前的闭锁程度和滑动亏损分布,结合龙门山断裂带附近地表水平应变率场结果,综合分析了震前地壳变形特征.反演结果表明,震前龙门山断裂中北段处于完全闭锁状态,闭锁深度达到21 km(闭锁比例0.99)左右,垂直断层方向的挤压滑动亏损速率约为2.2 mm/a,平行断层方向的右旋滑动亏损速率约为4.6 mm/a.龙门山断裂南段只有地表以下12 km闭锁程度较高(闭锁比例0.99),垂直断层方向滑动亏损速率约为1.4 mm/a,平行断层方向滑动亏损速率约为4.6 mm/a;在12~16 km处闭锁比例约为0.83,垂直断层方向滑动亏损速率约为1.2 mm/a,平行断层方向滑动亏损速率约为3.8 mm/a;在16~21 km处闭锁比例约为0.75,垂直断层方向滑动亏损速率约为1.1 mm/a,平行断层方向滑动亏损速率约为3.5 mm/a.在21~24 km处整条断裂均逐步转变为蠕滑.上述反演结果与区域应变计算获得的龙门山断裂带中北段整体应变积累速率较低、南段应变积累速率较高相一致,均表明中北段闭锁程度高、南段闭锁程度稍低,该特征可以较好地解释汶川地震时从震中向北东向单向破裂现象. 相似文献
10.
In order to analyze 3-dimensional movement and deformation characteristics and seismic risk of the Xianshuihe fault zone, we inverted for dynamic fault locking and slip deficit rate of the fault using the GPS horizontal velocity field of 1999-2007 and 2013-2017 in Sichuan-Yunnan region, and calculated annual vertical change rate to analyze the vertical deformation characteristics of the fault using the cross-fault leveling data during 1980-2017 locating on the Xianshuihe fault. The GPS inversion results indicate that in 1999-2007, the southeastern segment of the fault is tightly locked, the middle segment is less locked, and the northwestern segment is basically in creeping state. In 2013-2017, the southeastern segment of the fault is obviously weekly locked, in which only a patch between Daofu-Bamei is locked, and the northwestern segment is still mostly in creeping state, in which only a patch at southeastern Luhuo is slightly locked from surface to 10km depth. The cross-fault leveling data show that annual vertical change rate of the Zhuwo, Gelou, Xuxu and Goupu sites on the northwestern segment is larger, which means vertical movement is relatively active, and annual vertical change rate of the Longdengba, Laoqianning, and Zheduotang sites on the southeastern segment is small, which means the fault is locked, and the vertical movement changes little before and after the Wenchuan earthquake. Combining with the 3-dimensional movement and deformation, seismic activity and Coulomb stress on the Xianshuihe Fault, we consider the seismic risk of the southeastern segment is larger, and the Wenchuan earthquake reduced the far-field sinistral movement and the fault slip deficit rate, which may reduce the stress and strain accumulation rate and relieve the seismic risk of the southeastern segment. 相似文献
11.
—Measurements indicate that stress magnitudes in the crust are normally limited by the frictional equilibrium on pre-existing, optimally oriented faults. Fault zones where these limitations are frequently reached are referred to as seismic zones. Fault zones in the crust concentrate stresses because their material properties are different from those of the host rock. Most fault zones are spatially relatively stable structures, however the associated seismicity in these zones is quite variable in space and time. Here we propose that this variability is attributable to stress-concentration zones that migrate and expand through the fault zone. We suggest that following a large earthquake and the associated stress relaxation, shear stresses of a magnitude sufficient to produce earthquakes occur only in those small parts of the seismic zone that, because of material properties and boundary conditions, encourage concentration of shear stress. During the earthquake cycle, the conditions for seismogenic fault slip migrate from these stress-concentration regions throughout the entire seismic zone. Thus, while the stress-concentration regions continue to produce small slips and small earthquakes throughout the seismic cycle, the conditions for slip and earthquakes are gradually reached in larger parts of, and eventually the whole, seismogenic layer of the seismic zone. Prior to the propagation of an earthquake fracture that gives rise to a large earthquake, the stress conditions in the zone along the whole potential rupture plane must be essentially similar. This follows because if they were not, then, on entering crustal parts where the state of stress was unfavourable to this type of faulting, the fault propagation would be arrested. The proposed necessary homogenisation of the stress field in a seismic zone as a precursor to large earthquakes implies that by monitoring the state of stress in a seismic zone, its large earthquakes may possibly be forecasted. We test the model on data from Iceland and demonstrate that it broadly explains the historical, as well as the current, patterns of seismogenic faulting in the South Iceland Seismic Zone. 相似文献
12.
安宁河—则木河断裂带及东侧的大凉山断裂带作为大凉山次级块体西侧与东侧边界,具有发生大地震的活动构造背景.本文意在用有限的形变数据和地震数据两种资料评估大凉山次级块体边界断裂带的孕震深度及其地震危险性.采用弹性半空间模型对安宁河断裂、则木河断裂和大凉山断裂带滑动速率和闭锁深度进行了详细分析;计算了90%、95%和99%不同分位数的小震深度下界值并与GPS得到的闭锁深度进行对比,分析二者异同点.结果显示,安宁河断裂北段闭锁深度为6.2 km,不到90%分位小震震源深度16 km的一半,表明该段在1952年MS63/4地震后,断层逐渐趋于闭锁;而在6~16 km深度主要以小地震和无震滑动两种形式释放能量,存在深部蠕滑运动.大凉山断裂北段在0~10 km范围内完全闭锁,而10~25 km闭锁程度较弱.安宁河断裂南段、则木河断裂、大凉山断裂中段和南段均处于完全闭锁阶段,闭锁深度接近90%分位数小震深度的下界值,标准差约为0.94 km.此外,A、B、C三个剖面的反演结果表明大凉山次级块体的运动自北向南具有顺时针旋转特性,与川滇块体顺时针运动特征吻合.大凉山次级块体北、中、南三段边界断裂及块体内部总的滑动速率分别为9.8 mm·a-1、8.9 mm·a-1和8.4 mm·a-1,呈自北向南递减趋势.大凉山断裂南段布拖断裂和交际河断裂积累的能量分别能够发生一次矩震级为MW7.5的地震,离逝时间已经接近地震平均复发间隔,未来100年大地震的发震概率分别为7.1%和5.9%,应对其地震危险性给予重视. 相似文献
13.
THE VITRINITE REFLECTANCE OF FAULT ROCKS FROM THE WENCHUAN EARTHQUAKE FAULT ZONE: CONSTRAINTS ON FRICTIONAL PROPERTIES OF THE FAULT DURING THE EARTHQUAKE 
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下载免费PDF全文 YAO Lu MA Sheng-li WANG Yu HE Hong-lin CHEN Jian-ye YANG Xiao-song SHIMAMOTO Toshihiko 《地震地质》2016,38(4):817-829
The temperature rise caused by frictional heating during seismic slip is able to indicate dynamic frictional properties of the seismic fault,which provides an approach to understand the dynamic process and energy budget of an earthquake.The residual indicators of frictional heating within the fault zone also can be taken as an evidence for seismic events.The vitrinite reflectance is a commonly-used geothermometer in the coal,oil and gas industries.It also has some potential applications in the studies of fault rock and fault mechanics.We studied vitrinite reflectance (VR) of fault rocks collected from surface outcrops of the Wenchuan earthquake fault zone in this paper.The measured data reveal that the VR of fault rocks are affected by fault motion,and there is a trend that the VR increases towards the fault core,which indicates the effects of frictional heating.The VR of fault rocks from the Bajiaomiao outcrop is much higher than those from the Shenxigou outcrop,which probably suggests the difference in fault activity at the two outcrops.Our study also suggests that systematic measurement of VR across the fault zone is helpful in identifying slip zones and determining their widths.From the VR measurement on an oriented specimen containing the slip surface of the Wenchuan earthquake from the Shenxigou outcrop,we observed anomalous high VR values in two black-colored slip zones of about 2mm in width near the slip surface.The numerical calculation shows that the maximum temperature rise on the fault plane near Shenxigou was probably less than 162℃ during the Wenchuan earthquake,which means the dynamic fault strength was quite low.These estimations are roughly in accord with the results from the high-velocity frictional experiments. 相似文献
14.
本文以龙门山断裂带为背景，基于岩体应变能基本理论，使用FLAC软件模拟地震能量源和能量释放形式，计算结果显示:在0.01 MPa水平应力增量作用下，龙门山断裂带及附近区域可释放的应变能约为3.24×1013 J；使得断层面之间发生滑移，克服断层面滑动摩擦所需消耗的能量约为2.10×1013 J；岩体在重力方向上产生位移，克服重力做功所消耗的能量约为1.14×1013 J。由此可推断:在一定区域内，应力触发释放能量值与克服断层面滑动摩擦和克服重力做功所消耗的能量之和大致相当；应变能可能会在某一区域范围内集中释放，形成地震效应。本次应力增量触发断层周围岩体能量释放事件中，在映秀—北川断裂与灌县—安县断裂之间的局部区域集中释放的能量为7.67×1012 J，相当于一次MS5.39地震发生所释放的能量。 相似文献
15.
G. G. Kocharyan G. N. Ivanchenko S. B. Kishkina 《Izvestiya Physics of the Solid Earth》2016,52(4):606-620
Extensive data comprising about 1500 seismic events with the moment magnitudes MW from–3.5 to 9.2 have been analyzed for identifying the implications of the event size, the type of faulting in the source, and tectonic situations for the efficiency of the radiation. It is shown that there are several hierarchy levels with different patterns of scaling relationships describing the changes in the parameters of seismic events with the event size. This is due to the specificity of the hierarchy in the macroscopic characteristics of the rock mass. The size and mechanism of the earthquake determine the general trends in the variations of its radiation efficiency. The role of the macroscopic parameter controlling the efficiency of a seismic source is played by the stiffness of a fault or a fracture. The scaling relationship of this parameter determines several hierarchical levels within which the changes in the characteristics of the earthquakes follow the different laws. The huge scatter in the values of the scaled energy (the ratio of the radiated seismic energy to the seismic moment, energy-to-moment ratio) about the average requires additional study. Quite probably, the value of the scaled seismic energy is determined by the mesostructure and physicomechanical characteristics of the fault’s core. Small variations in these factors may lead to drastic changes in the stress drop amplitude and in the rupture propagation velocity up to the emergence of different regimes of deformation. 相似文献
16.
富蕴地震断裂带北部细部结构特征 总被引：1，自引：0，他引：1
以8级地震时的水平位移作为地震断裂带分段依据，富蕴地震断裂带北部引张段长17km，而且水平位移不明显。富蕴地震断裂带的主体走滑段水平位移显著，除大震时的水平位移外，发震构造具多期次活动特征。 相似文献
17.
2008年5月12日汶川MW7.9特大地震发生在龙门山断裂带，龙门山断裂带深部结构的复杂性制约了地震的破裂过程.通过对研究区区域地质、汶川地震前后采集的地震反射剖面等研究，在对龙门山北段汶川地震断裂带的深部结构和反射地震特征进行了分析的基础上，探讨了它对地表破裂过程的制约.研究结果表明，在地震剖面上，断裂带表现为能量破碎、联系性差；频率剖面上显示整体剖面频率在5~45 Hz，断裂带呈现频率低（15~26 Hz）等特征.龙门山北段映秀-北川断裂在10 km以上是一条倾向北西的高角度走滑兼逆冲性质的断裂，倾角50°~70°.它分割了西侧的轿子顶杂岩和东侧的唐王寨推覆体，错断了早期形成的逆冲岩片，从南到北总位移量由大变小.它高角度的几何形态约束了断裂以走滑为主兼逆冲分量的运动性质，降低了地表滑移量，影响了地震破裂过程以及余震沿断裂带两侧分布的特性. 相似文献
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Earthquake aftereffects and triggered seismic phenomena 总被引：5，自引：0，他引：5
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本文对龙门山断裂带金河磷矿浅钻岩芯中的三种断层泥开展了低速到高速摩擦滑动的实验研究，并对实验变形样品开展了BET比表面积研究.摩擦实验在干燥和孔隙水压条件下开展，速率范围涵盖20 μm·s-1~1.4 m·s-1.实验结果显示，三种断层泥在干燥条件下的摩擦性质差别不大，但在孔隙水压条件下，三者的中低速摩擦强度与层状硅酸盐矿物的种类而非总含量紧密相关，蒙脱石和伊利石相比绿泥石更能有效地弱化断层.三种断层泥在孔隙水压条件下存在中低速率域的速度强化，暗示着对断层的加速滑动存在一定的阻碍作用.孔隙水压下，黄绿色和灰绿色断层泥的初始动态弱化非常迅速并伴随断层泥层的瞬时扩容，凹凸体急剧加热导致的局部热压作用可能是造成这种力学行为的物理机制.在经历高速滑动之后，三种断层泥在干、湿条件下的BET比表面积都显著降低，暗示着可能发生了颗粒烧结.中低速域内，孔隙水的存在使得断层泥呈现分散式的剪切变形，BET比表面积的增加因此比干燥条件下更加明显.对表面能的估算表明，颗粒磨碎所消耗的能量至多不超过摩擦力做功的8%，暗示着断层作用中颗粒磨碎所占的能量比例较低. 相似文献