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1.
《地震地质》2013,(4)
汶川2008年M S8.0大地震同震地表破裂带中,近地表断层滑动面内多处分布了薄层断层泥。选取位于地表垂直位移量较大地段的北川沙坝探槽中的断层泥为研究对象,使用立体镜、光学显微镜和X光衍射等对断层泥微结构特征及其矿物成分进行详细的分析。结果表明:汶川地震地表破裂带的断层泥中发育Y-剪切、R1-剪切(与Y-剪切的交角14°)、R2-剪切、P-剪切以及张裂隙和书斜式构造等局部化脆性变形的特征显微构造。此外,断层泥中还有发育良好的P-叶理,碎屑颗粒的拉长和不对称拖尾构造等类似于散布的韧性变形特征。但是,它们仅局限在2条平行的Y-剪切之间发育,应当是断层同一滑动事件的产物。显微构造特征揭示了汶川地震破裂带的逆冲滑动性质,强烈变形的断层泥带较窄,仅约3mm,表明同震滑动明显地局限在一个窄的滑动带内。断层泥的石英和长石含量小于围岩,而黏土矿物含量高于围岩,说明来自围岩的长石和石英由于同震断层滑动摩擦使其部分转变为黏土矿物或黏土粒级的物质。断层泥中的伊利石含量高于围岩,伊利石/蒙脱石混层则低于围岩,这种黏土矿物组成成分的差异,可能是由于地震同震断层滑动摩擦增温(不排除溶液化学作用的参与),使部分伊利石/蒙脱石混层转化为伊利石。这些研究结果为探讨断层滑动性质提供了一种判定标准。 相似文献
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汶川地震断层岩的矿物学和地球化学特征揭示出地震断层经历了漫长时间演化和复杂的水岩相互作用.间震期水岩相互作用导致断层岩中的破碎矿物蚀变,尤其是长石等矿物含量渐渐减少甚至消失,而黏土矿物（蒙脱石、伊利石、伊/蒙混层、绿泥石等）含量逐渐增高,以及如黄铁矿、石膏、重晶石、坡缕石等热液系统中常见的矿物大量出现;Mg、P、Ti、Mn、Fe等元素倾向富集在断层带中,而Si、K和Na等出现明显的亏损;元素的大量迁移导致断层带的体积巨量亏损.实验结果表明,黏土矿物的亲水性引起水渗透率比干燥气体渗透率明显偏低,并且二者偏差无法通过Klinkenberg校正消除.蒙脱石吸水膨胀和黏土矿物颗粒表面吸附孔隙流体造成孔隙度降低是导致水渗透率偏低的重要原因.断层岩碎屑结构使得其中的孔隙可能在600 MPa围压下得以保存,从而有助于流体沿断层带下渗,并在断层带深部形成高流体孔隙压.地震断层的主要矿物学及粒度分布特征并非在地震破裂过程中形成,因此利用断层岩粒度分布资料估算地震破裂能并不合适. 相似文献
3.
2002年春季北京特大沙尘暴颗粒的矿物组成分析 总被引：4，自引：0，他引：4
应用X射线衍射(XRD)和带能谱的场发射扫描电镜(FESEM-EDX)对在北京2002年3月20日收集的一次特大亚洲沙尘暴样品进行了分析, 获得了矿物组成及粒度分布信息. 结果表明, 此次沙尘暴颗粒中矿物颗粒达94%. XRD半定量分析显示, 沙尘暴颗粒的矿物组成主要有黏土(40.3%)和石英(19.5%), 其次有方解石、斜长石、钾长石、赤铁矿、黄铁矿、角闪石和石膏, 但其含量都小于10%. 分离出的黏土组分中伊/蒙混层矿物占78%、伊利石9%、高岭石6%、绿泥石7%. FESEM-EDX分析除了检测到那些主要类型矿物外, 还检测出痕量的白云石、黄铁矿、盐类矿物芒硝、重矿物、金红石、钛铁矿和磷灰石等矿物. 此次亚洲沙尘暴颗粒和非洲撒哈拉大沙漠的沙尘羽颗粒的矿物类型相似, 但是黏土矿物组成有很大的差别, 前者以伊/蒙混层矿物为主, 后者以伊利石为主. 相似文献
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断层泥是断层错动的产物,成份往往比较混杂。含伊利石的断层泥是其中常见的一种。目前对常发生地震的5—15公里深处的断层泥特性了解甚少。本文通过含断层泥标本的高温高压实验结果,企图揭示一些断层泥在深部的特性。实验表明,在一定围压下伊利石断层泥在200℃和600℃时表现为无震稳滑,强度低。在350℃—480℃间表现为有震粘滑,强度高。对实验后的样品进行X射线衍射分析、差热分析和显微镜观察证明伊利石力学性质的变化与标本中含水情况的变化以及高温下的白云母化过程有关。进而讨论了蛇纹石、伊利石和其它粘土矿物在力学性状和矿物成份上的共性与个性。 相似文献
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地震后在断层两侧的强变形与破裂带是地震灾害最严重的区域.为系统、定量研究同震地表变形带特征及其影响因素,本研究建立了走滑断层的三维有限元模型,分别探讨了断层位错量、断层倾角、错动方式、上覆松散层厚度、沉积层土性等因素的影响规律.模拟结果显示：走滑断层同震地表变形表现为以断层为中心的近似对称单峰分布,强地表变形集中在断层两侧各50 m宽度范围,地表变形量峰值随位错量增加而增大,破裂带宽度也随位错量增加而增大,但增量逐渐减小,并趋于一个渐近值;断层倾角对地表变形与破裂带宽度影响表现为随倾角减小变形量峰值点向上盘小距离偏移;走滑兼正断位错引起的变形量峰值最大,但地表破裂带宽度最小,走滑兼逆断引起的变形量峰值最小,但地表破裂带宽度最大,直立纯走滑断层的两参量都居中;走滑断层地表变形量峰值随上覆松散层厚度增大而减小,但随厚度减小的速率逐渐变小,松散层厚度从5 m增加到20 m时,破裂带宽度随厚度增加而缓慢增加,但自厚度大于20 m时,破裂带宽度开始随厚度增加而逐渐下降;当不同土性覆盖层（粗砂、粉砂、黏土）厚度相同时,地震引起的地表变形量峰值自粗砂、粉砂、黏土逐次增大,当粗砂厚度为60 m以上时,3.6 m的同震水平位错已不能形成地表破裂,而粉砂的厚度为70 m以上,黏土的厚度则为75 m以上. 相似文献
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同震地表破裂带的空间展布及形变特征是地球深部断层活动在地表的直观地貌表现,不但记录着地震破裂和断层运动的信息,还反映了区域应力和地壳运动状况.因此,开展震后地震地表破裂带调查对于了解发震断层的构造活动尤为重要.高精度地形观测技术可以获取前所未有的高时空分辨率的地球表面特征,为辨别历史地震地表破裂遗迹、提取地表同震位移、活动构造地质填图等提供高质量数据.文中选取富蕴1931年地震地表破裂带作为研究区,利用SfM(Structural from Motion)摄影测量技术生成分辨率为1 m的数字高程模型(DEM),详细识别地表破裂并测量冲沟的右旋位移.基于地表破裂的几何及构造地貌特征,将富蕴地震地表破裂带由北向南分为S1、S2、S3、S44段,其间以挤压隆起或拉分盆地相连接.沿破裂带共获得194组最新冲沟的右旋水平位移,得到1931年同震位移的平均值为(5.06±0.13)m.同震位移局部缺失或突变的区域与几何阶区的位置也有良好的对应关系.以上结果填补了对富蕴地震地表破裂精细形态研究的空白,也进一步展示高分辨率的地形数据在活动构造研究中良好的应用价值. 相似文献
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断层带内的流体不仅可以通过水岩反应改变断裂岩的矿物组成和化学成分,从而导致化学性质和物理性质的变化,而且可以影响或控制断裂带的变形行为.断裂带中岩石磁学特征是由特定化学环境下磁性矿物的种类和含量所决定的,因此,从矿物学和地球化学角度探讨断裂岩的磁性变化,对揭示断层的变形行为和环境具有一定的指示作用.本文以汶川科钻WFSD-3P钻孔中龙门山灌县—安县断裂带断裂岩为研究对象,运用高分辨率磁化率测试、XRD矿物成分半定量分析、XRF元素扫描以及不同价态Fe元素含量分析等多种方法开展断层磁学变化和变形环境的研究.磁化率测试结果表明灌县—安县断裂带断层泥的磁化率值普遍低于对应的围岩磁化率平均值.结合前人研究成果表明造成该断层泥低磁化率异常的原因是在间震期的长期流体作用下,铁磁性矿物（例如磁铁矿）转变成顺磁性矿物（铁硫化物、菱铁矿或含铁的黏土矿物）.新生铁硫化物和含铁黏土矿物是在间震期缓慢形成的,而黏土矿物含量的增加弱化了断层强度,促进断层蠕滑,这说明断层泥低磁化率异常可能指示了该断裂在间震期长期缓慢活动,即为蠕滑变形.断层泥中黄铁矿的发育和高Fe2+和S元素、低Fe3+的特征显示灌县—安县断裂作用环境通常是在低温、还原环境中进行的.这些结果与低磁化率值的相关性暗示断层泥低磁化率异常可能对活动断层的低温还原环境具有指示意义. 相似文献
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《地震地质》2016,(3)
2008年汶川地震、2010年玉树地震、2014年鲁甸地震等大量震例研究表明,严重的地震灾害损失和人员伤亡主要源于发震断层的同震地表破裂、近断层的强地面运动和地基失效引起的建(构)筑物倒塌。因此,避让活动断层是有效减轻可能遭遇的地震灾害损失的一项重要措施。但如何避让活动断层和避让多少距离能够保证地面建(构)筑物不受活动断层同震错动引起的直接毁坏,一直是国内外学者争论的焦点科学问题。1)首先基于历史地震地表破裂资料,定量分析了活动断层同震地表破裂的局部化特征、同震地表破裂与建(构)筑物的破坏关系,得出了地震地表破裂带及其直接严重地震灾害带宽度的平均统计值约为30m的认识。2)通过1999年集集地震、2008年汶川地震等地表破裂带宽度资料和地震灾害空间分布关系的分析,指出了倾滑断层具有明显的上盘效应,断层上、下盘地表破裂带或严重地震灾害带宽度之比为2︰1至3︰1。3)基于上述分析获得的最新认识,进一步讨论了避让对象、活动断层定位要求、不同类型活动断层最小避让距离、特殊建(构)筑物避让和"抗断"设计理念等问题。最后,呼吁立法机构加强活动断层避让和活动断层探测的立法工作,规范活动断层上及其邻近地段土地利用规划和基础设施建设过程中合理避让活动断层的行为,防患于未然,提高中国防震减灾的基础能力。 相似文献
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始新世是全球气候从"温室"转化为"冰室"的一个重要时期,亚洲内陆在该时期发生了青藏高原隆升、副特提斯海海退等重大地质事件.位于青藏高原东北缘的西宁盆地具有连续完整的始新世河湖相沉积地层,以红色泥岩夹石膏层为主,记录了该时期的气候变化.本研究采用X射线衍射仪(XRD)对西宁盆地西箕沟剖面始新世河湖相沉积样品进行全岩及黏土矿物定性、半定量分析,以获取青藏高原东北缘及亚洲内陆地区始新世时期的古气候变化特征.为了有效解决目前通用的黏土矿物提取方法难以从石膏层中提取足量黏土的问题,引入一种新的黏土矿物提取方法.结果表明,西宁盆地始新世样品中主要矿物为石英、长石、方解石、白云石以及石膏;黏土矿物为伊利石、绿泥石及蒙脱石(含伊蒙混层矿物(I/S)).黏土矿物相对含量变化表明,始新世时期西宁盆地古气候在较为干旱的背景下经历了三次相对湿润的时段:52～50、41.5～39、35～34Ma.通过与同时期的深海氧同位素记录、副特提斯海海侵-海退事件以及青藏高原隆升等进行对比分析发现,西宁盆地始新世古气候主要受控于全球气候变化. 相似文献
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FRICTIONAL PROPERTIES OF A NATURAL FAULT GOUGE FROM DRILLED CORES IN THE LONGMENSHAN FAULT ZONE CUTTING GRANITIC ROCK 
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下载免费PDF全文 In this paper, we report friction experiments performed on natural fault gouge samples embedded in granitic rock from drilled core by a project entitled "the Longmenshan Fault Shallow Drilling(LMFD)". Compared with other natural fault gouge, this yellow-greenish gouge(YGG)is dominantly chlorite-rich. The maximum content of chlorite reaches 47%in the YGG. To understand the frictional properties of the YGG sample, experiments were performed at constant confining pressure of 130MPa, with constant pore pressure of 50MPa and at different temperatures from 25℃ to 150℃. The experiments aim to address the frictional behavior of the YGG under shallow, upper crustal pressure, and temperature conditions. Compared with previous studies of natural gouge, our results show that the YGG is stronger and shows a steady state friction coefficient of 0.47~0.51. Comparison with previous studies of natural gouge with similar content of clay minerals indicates a sequence of strengths of different clay minerals:chlorite > illite > smectite. At temperatures up to 150℃ hence depths up to~8km in the Longmenshan region, the YGG shows stable velocity-strengthening behavior at shallow crustal conditions. Combined with the fact of strong direct velocity effect, i.e., (a-b)/a>0.5, faults cutting the present clastic lithology up to~8km depth in the Longmenshan fault zone(LFZ)are likely to offer stable sliding resistance, damping co-seismic rupture propagating from below at not-too-high slip rates. However, as the fault gouge generally has low permeability, co-seismic weakening through thermal pressurization may occur at high slip rates(>0.05m/s), leading to additional hazards. 相似文献
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断层岩,尤其是断层泥的磁性异常近年来被研究人员广泛关注,但关于其磁性异常的形成原因尚没有统一的解释．海原断裂是青藏高原东北缘一条重要的走滑断裂,前期研究发现海原断裂带景泰段出露有数十米至上百米的断层岩,是理想的研究材料．本研究选取海原断裂带景泰段老虎山山前一个断层岩剖面作为研究对象,拟通过测量断层岩的磁化率（χ）、非磁滞剩磁（ARM）、饱和等温剩磁（SIRM）、等温剩磁（IRM）以及磁化率随温度变化曲线（χ-T曲线）等磁学参数并结合粒度、碳含量、X射线衍射（XRD）等分析方法来探究海原断裂带老虎山段不同颜色断层岩的磁性特征及其形成机制．磁学研究显示黑色、红色及杂色断层泥相较于围岩和破碎带显示了低磁性,尤其是黑色断层泥,其磁化率值均小于10×10~(-8 )m~3·kg~(-1)．碳含量及矿物相分析结果指示黑色断层泥与断裂带附近石炭系煤层具有相似的矿物相组成,结合相似的χ-T曲线推断石炭系煤层为黑色断层泥的母岩．石炭系煤层经断层活动卷入断层,在断层强烈剪切摩擦作用下不断细化,形成伊利石等黏土矿物,并促使一部分顺磁性含铁硅酸盐矿物或其他含铁矿物发生化学变化形成亚铁磁性矿物,使得黑色断层泥的磁化率较其母岩石炭系煤层有一定升高．通过黑色断层泥的铁磁性磁化率结合χ-T曲线计算获得断层泥所经历的最高温度约为420℃,不超过450℃．老虎山段厚层碳质断层泥的存在为该地区发现的浅层蠕滑现象提供了一种解释． 相似文献
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THE GEOLOGICAL AND ROCK MECHANICAL DISTINCTION EVIDENCE BETWEEN STICK-SLIP AND CREEP IN HOST ROCK SEGMENTS OF FAULT 下载免费PDF全文
下载免费PDF全文 ZHOU Yong-sheng 《地震地质》2019,41(5):1266-1272
Paleo-seismic and fault activity are hard to distinguish in host rock areas compared with soft sedimentary segments of fault. However, fault frictional experiments could obtain the conditions of stable and unstable slide, as well as the microstructures of fault gouge, which offer some identification marks between stick-slip and creep of fault.
We summarized geological and rock mechanical distinction evidence between stick-slip and creep in host rock segments of fault, and analyzed the physical mechanisms which controlled the behavior of stick-slip and creep. The chemical composition of fault gouge is most important to control stick-slip and creep. Gouge composed by weak minerals, such as clay mineral, has velocity weakening behavior, which causes stable slide of fault. Gouge with rock-forming minerals, such as calcite, quartz, feldspar, pyroxene, has stick-slip behavior under condition of focal depth. To the gouge with same chemical composition, the deformation mechanism controls the frictional slip. It is essential condition to stick slip for brittle fracture companied by dilatation, but creep is controlled by compaction and cataclasis as well as ductile shear with foliation and small fold. However, under fluid conditions, pressure solution which healed the fractures and caused strength recovery of fault, is the original reason of unstable slide, and also resulted in locking of fault with high pore pressure in core of fault zone. Contrast with that, rock-forming minerals altered to phyllosilicates in the gouges by fluid flow through degenerative reaction and hydrolysis reaction, which produced low friction fault and transformations to creep. The creep process progressively developed several wide shear zones including of R, Y, T, P shear plane that comprise gouge zones embedded into wide damage zones, which caused small earthquake distributed along wide fault zones with focal mechanism covered by normal fault, strike-slip fault and reverse fault. However, the stick-slip produced mirror-like slide surfaces with very narrow gouges along R shear plane and Y shear plane, which caused small earthquake distributed along narrow fault zones with single kind of focal mechanism. 相似文献
14.
在不同的压力、温度和孔隙压力下进行了含四种不同断层泥标本的强度试验。碎屑型断层泥对压力很敏感,对温度无反应,对孔隙压力的反应符合有效应力律。粘土类断层泥则对温度和孔隙压力有明显响应。这些力学性质的差别反映了具体变形机制的差别 相似文献
15.
Koichiro Fujimoto Hidemi Tanaka Takayuki Higuchi Naoto Tomida Tomoyuki Ohtani Hisao Ito 《Island Arc》2001,10(3-4):401-410
Abstract Mineralogical and geochemical studies on the fault rocks from the Nojima–Hirabayashi borehole, south-west Japan, are performed to clarify the alteration and mass transfer in the Nojima Fault Zone at shallow depths. A complete sequence from the hornblende–biotite granodiorite protolith to the fault core can be observed without serious disorganization by surface weathering. The parts deeper than 426.2 m are in the fault zone where rocks have suffered fault-related deformation and alteration. Characteristic alteration minerals in the fault zone are smectite, zeolites (laumontite, stilbite), and carbonate minerals (calcite and siderite). It is inferred that laumontite veins formed at temperatures higher than approximately 100°C during the fault activity. A reverse component in the movement of the Nojima Fault influences the distribution of zeolites. Zeolite is the main sealing mineral in relatively deep parts, whereas carbonate is the main sealing mineral at shallower depths. Several shear zones are recognized in the fault zone. Intense alteration is localized in the gouge zones. Rock chemistry changes in a different manner between different shear zones in the fault zone. The main shear zone (MSZ), which corresponds to the core of the Nojima Fault, shows increased concentration of most elements except Si, Al, Na, and K. However, a lower shear zone (LSZ-2), which is characterized by intense alteration rather than cataclastic deformation, shows a decreased concentration of most elements including Ti and Zr. A simple volume change analysis based on Ti and Zr immobility, commonly used to examine the changes in fault rock chemistry, cannot account fully for the different behaviors of Ti and Zr among the two gouge zones. 相似文献
16.
汶川8.0级地震发震断层的累积地震位错研究 总被引：1，自引：0，他引：1
2008年5月12日,四川省汶川县内发生MS8.0地震。此次地震沿龙门山中央断裂产生1条长达200km的同震地表破裂带。文中选择位于地震地表破裂带北段的南坝镇、凤凰村以及南段的映秀镇这3个地点,以被断层错断的河流阶地为研究对象,对多级阶地面上的地震地表破裂及断层陡坎地貌进行了野外实测工作。经过测量数据的计算和分析,得到了各级阶地上断层陡坎的高度,该值即为该阶地记录的地震断层的累积垂直位错量。若以本次地震的垂直位错量作为古地震位错量的均值,则可计算得到每级阶地累积的地震次数。研究结果表明,各点T1阶地形成以来仅经历过1次事件,即本次地震事件;T2阶地形成以来约经历了5次事件;T3阶地形成以来约经历了9～11次事件;T4阶地形成以来约经历了20次事件。在本文研究的基础上,结合前人的阶地测年数据,则可获得古地震复发间隔的可靠数据 相似文献
17.
James R. O'Neil 《Pure and Applied Geophysics》1984,122(2-4):440-446
Measurements were made of the amounts of D,18O, and H2O+ in fault gouge collected over a depth of 400 m in the San Andreas fault of California. The amounts and isotopic compositions of the pore fluids, also analyzed, suggest that formation waters from adjacent Franciscan rocks have migrated into the gouge and mixed with local meteoric water. Thus the gouge is an open system permeable to fluid flow. This permeability has important implications concerning heat flow along the fault zone.Analyses of the fault gouge itself give information on the amounts, timing, and conditions of formation of the clay minerals.Stable-isotope analyses of materials from fault zones are good indicators of water-rock interactions that bear importantly on processes taking place in seismically active regions. 相似文献
18.
Francis T. Wu 《Pure and Applied Geophysics》1978,116(4-5):655-689
Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones. The 2-microns fractions in these fault gouges may compose a few percent to more than fifty percent of the total mass in the outcrops, and the mineralogy of the 2-microns fractions consists of a variety of clays (the common ones are montmorillonite, illite, kaolinite, chlorite, vermiculite and mixed-layer clays) and some quartz, feldspars, etc.Although we cannot yet conclude directly from the studies of gouges that similar gouges exist at depths where many large shallow earthquakes are generated, there is a strong possibility that they do, based on (1) available equilibrium data on various clays — for example, kaolinite has been found to exist at 4 kb and 375°C (±15°C) (Thompson, 1970) and montmorillonite + kaolite has been found to exist at 450°C and 4 kb (Velde, 1969); (2) the compatibility of laboratory velocity data in gouge (Wang
et al., 1977) with those in a model for central California (Healy andPeake, 1975); (3) the capability of clays to undergo sudden earthquake-like displacements (Summers andByerlee, 1977); (4) the petrology of intrafault cataclastic rocks in old fault zones (Kasza, 1977); and (5) the compatibility of gouge mineralogy with the mineralogy of hydrothermal clay deposits.If clay gouges are indeed significant components of the fault zone at depth, then the mechanical properties of clays under confining pressures up to 4 kb are important in the behavior of faults. Very few experiments have been performed under such high pressures. But from the physical makeup of clays, we can infer that (1) the range of possible behavior includes stable sliding with vermiculite and montmorillonite (asByerlee andSummers, 1977, have proven) to stick-slip-like behavior with kaolinite, chlorite, etc.; (2) the absence or presence of water will greatly affect the strengths of gouges — it is possible that water may reduce the strength of gouge to a fairly small value. 相似文献