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应用双剪法对滇西地震实验场岩石的摩擦滑动特性进行了研究。实验的岩石有花岗岩、玄武岩、正长岩和片麻岩。实验的正应力为10—40MPa。实验表明,花岗岩、玄武岩和正长岩三种岩石,当正应力为10MPa时发生稳滑,当正应力超过10MPa时发生粘滑。稳滑与粘滑过程均出现位移强化现象。片麻岩当正应力为10MPa时发生稳滑,当正应力超过10MPa时样品未滑动而发生破裂。摩擦强度值比Byerlee定律的值稍低。与济南辉长岩相比,滇西三种岩石粘滑发生时的平均应力降较低,平均错距较小,平均重复周期较短。花岗岩粘滑前声发射率明显增加,玄武岩与正长岩粘滑前声发射率变化不明显。 相似文献
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众所周知.岩石的摩擦滑动有两种方式,一种是粘滑,另外一种是稳滑.当发生粘滑时,应力突然下降并伴随有急剧的能量释放.从1966年 Brace 等人指出粘滑可能是导致浅源地震的原因以来,粘滑作为一种震源机制已引起地震学家的普遍关注.但是,粘滑的研究还有许多问题,如粘滑发生的条件,围压对粘滑及其应力降的影响,特别是室内粘滑实验应力降远高于天然地震应力降这一问题,到目前还没有解决(陈顒,1988).本文建立了一个岩石摩擦的自锁模型,这一模型能够反映围压与粘滑之间的关系.分析结果表明,天然地震应力降低于室内粘滑实验应力降是由围压刚度引起的. 相似文献
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2008年5月12日中国汶川发生了MW7.9地震,全球数字地震仪台网（GSN）74个台的地震仪和陕西周至地震台的数字水位仪都很好地记录到了该地震的同震粘滑错动过程和止滑过程。分析GSN 74个地震台的记录后发现：汶川MW7.9地震的同震粘滑错动过程是一次多点粘滑错动过程,主要由四个子粘滑错动事件构成,整个粘滑错动过程的持续时间不少于86.6 s;地震的弹性破裂过程与粘滑错动过程同时进行,是粘滑错动和弹性破裂共同作用的结果,是一种"粘滑错动+弹性破裂"的机制。对周至地震台数字水位仪记录分析后发现：汶川地震的同震粘滑错动过程与P.N.Sundaram[1]作的岩石粘滑错动实验结果一致,粘滑错动过程可细分为粘结（stick）和滑动（slip）二个过程。汶川地震在止滑过程中激发出了长周期勒夫面波（XsQ）和瑞雷面波（XsR）。研究粘滑震相有助于认识震源的粘滑错动过程,研究止滑震相有助于预判震灾损失。 相似文献
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断层阶区对滑动行为影响的实验研究 总被引：1，自引：0，他引：1
研究断层带几何非规则体对断层活动的力学影响,对于理解断层带上的地震活动具有重要的理论和实际意义．通过中尺度标本岩石力学实验,研究了走滑断层带最常见的一种非规则体．断层阶区对滑动行为的影响．研究表明,拉张断层阶区由于强度较低而很容易发生破裂,破裂后的阶区对断层的滑动无明显阻碍作用,但阶区的微破裂对断层滑动失稳具有指示作用;含拉张阶区的断层带具有速度弱化特征,可用速率一状态摩擦定律表述．挤压阶区由于破坏强度很高,使得断层滑动较为困难,但随着应力水平的增加,阶区外断层端部拉张区的微破裂为断层在阶区未破裂之前发生粘滑失稳提供了变位条件,并因此可作为断层失稳的前兆;挤压阶区可作为断层分段的稳定标志,直到阶区完全破裂使两条断层完全连通． 相似文献
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《地球物理学进展》1990,(2)
本文评述了岩石摩擦研究及其在地震震源研究中的应用.当前的岩石摩擦研究已经认识到由静摩擦变成动摩擦时其摩擦阻力减少的比率是有限的.很多岩石的摩擦状况已用滑动距离和/或与滑动速率有关的本构关系进行了描述.许多研究工作已经表明,表面粗糙程度在摩擦规律中起重要作用,并已指出,断层粗糙度可能是诸如临界衰减滑动位移和剪切破裂的视破裂能量等与体积大小有关的物理参量的一个来源.地震断裂的数值模型是用一个摩擦本构定律来表达的.这些模型不仅可以模拟地震的强运动,而且也可以模拟地震的前兆清动.这些结果对滑动的不稳定性给出了一个较好的解释,也导致了对于地震发生过程的更深刻了解. 相似文献
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采用断层位错模式,考虑了具有一定宽度的断层在其粘滑过程中,断层摩擦应力和滑动速度随粘滑过程的变化情况,由此计算了粘滑所产生的摩擦增温,并将结果与不考虑摩擦应力变化、不考虑滑动速度变化或忽略断层宽度时的情况作了比较。结果表明:断层滑动时,摩擦应力和滑动速度随时间的改变及断层的宽度将对断层摩擦增温产生较大影响。由于岩石中孔隙和孔隙流体的存在,摩擦应力在断层粘滑过程中有较大变化。取断层滑动速度为Brune 震源时间函数形式,考虑摩擦应力的变化及一定的断层宽度,计算得到的摩擦增温值较以往的计算结果偏小。这个结论对测定断层活动年代的热释光(TL)和电子自旋共振(ESR) 法具有一定的理论指导意义 相似文献
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固体围压下完整花岗岩粘滑现象的实验研究 总被引：3，自引：0，他引：3
本文用完整的花岗岩样品在固体围压三轴实验装置上压缩,研究围压和应变速率对岩样变形破裂过程、粘滑应力降、粘滑复发间隔及样品主破裂几何分布的影响。结果表明,加载速率较低时,粘滑应力降较大,复发间隔较长且分布无规律。加载速率越大,粘滑应力降越小,复发间隔也近似相等,粘滑事件表现出准周期性。围压和应变率较低时,岩石的主破裂会演变成两个交叉的共轭断裂面;而围压和应变率较高时,岩石的主破裂则演变成单一断裂面或入字形断裂面。本文结果对认识中国大陆板内地震孕育、发生及重复过程;研究地震重复发生的机制及影响地震复发间隔的主要因素都有重要意义。 相似文献
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M. N. French R. L. Bras W. F. Krajewski 《Stochastic Environmental Research and Risk Assessment (SERRA)》1992,6(1):27-45
A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities. 相似文献
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Gtz Schroth Luciana Ferreira Da Silva Marc‐Andree Wolf Wenceslau Geraldes Teixeira Wolfgang Zech 《水文研究》1999,13(10):1423-1436
The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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M. A. Kahn 《洁净——土壤、空气、水》2000,28(2):95-101
Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate. 相似文献