共查询到17条相似文献，搜索用时 156 毫秒
1.
断层地震孕震的椭圆形区域及其前兆规律 总被引：2，自引：2，他引：2
首先运用岩石介质的损伤本构关系式和断层地震的简单力学模型，讨论了断层和围岩介质系统的相互作用及其失稳过程，通过差分计算，得到了与地震变形和声发射等有关的前兆序列曲线，然后根据实际断层带滑移与错动的分布规律，通过计算机模拟出断层地震的椭圆形孕震区并此解释了Ｐ波初动分布规律。 相似文献
2.
利用曲线网格有限差分方法,研究了三维倾斜断层的破裂传播过程.基于断层面生成贴体曲线网格,并通过坐标变换将含曲线网格的物理空间转换到含均匀直角网格的计算空间,实现了有限差分方法对复杂界面的处理.通过模拟地震断层的自相似破裂和自发破裂,并与已有发表的结果对比,发现拟合程度较高,验证了本方法的有效性和精确性.重点研究了不同倾角的倾斜断层破裂,最后展望了今后用本方法对非均匀介质中和任意起伏地表下的任意非平面断层破裂动力学的进一步研究. 相似文献
3.
在以前的工作中,考虑直立走滑型断层地震,假设断层面微元破裂强度遵循Weibull概率分布,由细观力学方法推导出断层面的宏观本构关系是一个非线性函数,表现为弹性-软化塑性特征,在此基础上用稳定性理论研究了地震稳定性问题.而实际断层大多是倾斜的,为此,本文首先建立了由围岩和倾斜断层构成的平面地震力学模型,采用宏观的断层载荷-变形的全过程曲线,详细讨论了倾斜断层地震的不稳定性问题.结果表明,远场一旦施加位移,断层也同时错动,这可能与实际情况不符合.为了更好的模拟断层的初始能量累计过程,进一步对断层本构模型进行改进.考虑断层面破裂强度,采用Coulomb破裂准则,则断层表现为刚塑性本构关系,只有当断层面剪应力达到一个临界值时,断层才开始错动.研究表明,对于倾斜断层地震,与直立走滑型断层地震一样,系统刚度比β(围岩切线刚度与断层刚度最大值之比)是决定地震失稳的重要参数,只有当β1时才会出现地震失稳,且伴随应力突跳和围岩应变能释放.当β≥1时,仅仅是断层无震滑动,不会发生地震.在远场应施以位移形式边界条件,以致地震失稳发生在平衡路径的位移转向点并伴有应力突跳. 相似文献
4.
在以前的工作中,考虑直立走滑型断层地震,假设断层面微元破裂强度遵循Weibull概率分布,由细观力学方法推导出断层面的宏观本构关系是一个非线性函数,表现为弹性-软化塑性特征,在此基础上用稳定性理论研究了地震稳定性问题.而实际断层大多是倾斜的,为此,本文首先建立了由围岩和倾斜断层构成的平面地震力学模型,采用宏观的断层载荷-变形的全过程曲线,详细讨论了倾斜断层地震的不稳定性问题.结果表明,远场一旦施加位移,断层也同时错动,这可能与实际情况不符合.为了更好的模拟断层的初始能量累计过程,进一步对断层本构模型进行改进.考虑断层面破裂强度,采用Coulomb破裂准则,则断层表现为刚塑性本构关系,只有当断层面剪应力达到一个临界值时,断层才开始错动.研究表明,对于倾斜断层地震,与直立走滑型断层地震一样,系统刚度比β（围岩切线刚度与断层刚度最大值之比）是决定地震失稳的重要参数,只有当β<1时才会出现地震失稳,且伴随应力突跳和围岩应变能释放.当β≥1时,仅仅是断层无震滑动,不会发生地震.在远场应施以位移形式边界条件,以致地震失稳发生在平衡路径的位移转向点并伴有应力突跳. 相似文献
5.
对一个地震突变模型的讨论 总被引：4，自引：0，他引：4
本文用非线性力学方法讨论了地震过程的非稳定现象并建立了相应的突变理论模型。文章详细讨论了断层带的本构性质和突变模型中状态变量的选取对地震非稳性的影响，揭示了用突变模型研究地震现象的可行性。 相似文献
6.
本文对郯庐断裂带大水场黄绿色粘土型断层泥进行了一系列实验研究并初步探讨了其本构特征。该本构模型能描述断层泥的弹性性态。破坏性态和帽盖性态,适应范围较广。 相似文献
7.
本文把Jeny D.Jones(1982)的断层应变软化模型推广到非均匀应变软化和滑动偏转情形,并研究了其失稳条件。研究表明,除断层本构律外,断层非均匀应变软化及其滑动偏转是影响不稳定判据的两个重要因素,真实地模拟断层非均匀应变软化、滑动偏转过程和合适的断层本构律有可能会提高预报强震发震时间的准确性。 相似文献
8.
9.
基于断层面强度的非均匀性,将断层面的宏观破裂过程看作是断面局部微元的破裂累积过程,假设断层局部微元强度遵循Weibull概率分布,从统计力学角度推导出了宏观的断层载荷.变形的全过程本构关系.采用一维地震力学模型,以远场位移a为控制变量,用稳定性理论研究了地震不稳定性问题.研究表明,系统刚度比(围岩刚度与断层刚度之比)β是影响地震发生的重要参数,只有当β<1时才会出现地震失稳,且应力突跳发生在平衡路径曲线的位移转向点,并给出了地震过程的3个重要参数(地震后断层半错距、地震应力降和释放的弹性能)的表达式.当β≥1时,不会发生地震,仅是缓慢的断层滑动,属于无震滑动. 相似文献
10.
11.
In this paper, we studied the slip-weakening instability on a finite and vertical strike-slip fault with asperity. We assumed
that the fault strength is uniform in depth, but it is non-uniform in the strike direction, i.e., there is an asperity on
the fault. The segments of the fault with and without asperity follow the same type of constitutive law, but the peak stresses
are different. The material surrounding the fault is represented by elastic plates whose upper-surface and bottom are stress-free.
We use finite element method to study the evolution of theoretical displacement, stress and strain fields that vary with a
remote displacement. Here the displacement and frictional stress are not given in advance, but are determined in the solving
process. According to the results, we compared the theoretical displacemeut and the distribution of frictional stress on the
fault between the stable and unstable slips. In addition, we compared the results in this paper with known results for the
strike-slip fault with a segment of lower strength. 相似文献
12.
本文研究了有限长度含有单一粗糙面的垂直走滑断层的滑动弱化不稳定性.我们假定断层强度在其深度方向是均匀的,而在走滑方向是不均匀的,即存在一个高强度段.并假定断层上的粗糙段及断层上的其它部分具有相同类型的本构律,只是峰值应力不同.断层周围的地壳材料用上、下表面应力自由的弹性平板来模拟.我们用有限元方法研究了理论位移场、应力场和应变场随远场位移的演变情况.此时,断层位移和摩擦应力并不是预先给定的,而是在求解过程中同时确定的.根据计算结果,我们比较了理论位移场及断层上摩擦应力分布在稳定和不稳定滑动情况时的差别.并与内部含有低强度段的走滑断层的场合做了比较. 相似文献
13.
Slip-softening instability on a vertical strike-slip fault with asperities has been analysed. The fault strength is uniform in depth, but the strength is nonuniform in the strike direction, i.e., there are asperities on the fault. These asperities and other segments of the fault have the same type of constitutive law but different peak stresses. The material surrounding the fault is represented by elastic plates, of which the top and bottom surfaces are stress-free.We use a finite element method to study the evolution of theoretical displacement, stress and strain field with a growing displacement applied at the remote plate ends. The slip and frictional stress are obtained as part of the solution. We have compared the difference of theoretical displacement, strain field and the distribution of frictional stress on the fault between unstable and stable slip. In addition, we have studied the effect of size and strength of asperities on instability, and the softening behaviour of asperities before instability.We find that (1) the failure of the fault zone may be due to either dynamic instability or rapid quasistable slip. A general characteristic of unstable mode is that slippage, on some parts of asperities increases indefinitely for a small finite increase in remote imposed displacement until, immediately before the unstable slip; (2) the size and peak strength of asperities have a large effect on instability. Reducing the size and peak strength of asperities tends to replace inertially unstable deformation with stable deformation; (3) the location with maximum acceleration during unstable slip, as the plausible nucleating seismic source, is in asperities; (4) the shapes of the changes in theoretical stress and strain at a given location, caused by the nonlinear constitutive property of the fault, are all similar whether instability, happens or not. This fact suggests that the changes of peak type or bend type in crustal deformation are not required for earthquake instability. 相似文献
14.
William D. Stuart 《Pure and Applied Geophysics》1988,126(2-4):619-641
An earthquake instability model is formulated for recurring great earthquakes at the Nankai Trough subduction zone in southwest Japan. The model is quasistatic, two-dimensional, and has a displacement and velocity dependent constitutive law applied at the fault plane. A constant rate of fault slip at depth represents forcing due to relative motion of the Philippine Sea and Eurasian plates. The model simulates fault slip and stress for all parts of repeated earthquake cycles, including post-, inter-, pre- and coseismic stages. Calculated ground uplift is in agreement with most of the main features of elevation changes observed before and after the M=8.1 1946 Nankaido earthquake. In model simulations, accelerating fault slip has two time-scales. The first time-scale is several years long and is interpreted as an intermediate-term precursor. The second time-scale is a few days long and is interpreted as a short-term precursor. Accelerating fault slip on both time-scales causes anomalous elevation changes of the ground surface over the fault plane of 100 mm or less within 50 km of the fault trace. 相似文献
15.
John W. Rudnicki 《Pure and Applied Geophysics》1988,126(2-4):531-554
This paper selectively reviews physical models of earthquake instability. In these models, instability arises as a result of interaction of a fault constitutive relation with deformation of the surrounding material that occurs in response to remote tectonic loading. In contrast to kinematic models in which the fault slip is imposed, it is calculated in physical models and, consequently, these models are essential for understanding precursory processes. Some kind of weakening behavior for the fault constitutive relation is required to produce an instability analogous to an earthquake. Two commonly employed idealizations discussed here are rate-independent slip weakening and rate/state-dependent friction. When these constitutive models are employed on surfaces embedded in elastic half-spaces or layers, possibly coupled to a viscoelastic substrate, the results are capable of simulating realistically some aspects of earthquake occurrence. Common to all models is the prediction that earthquake instability is preceded by precursory slip which produces a departure of surface strain-rate from the background level. Near the epicenter of a moderate to large earthquake, the magnitude of this departure appears to be well within the range of current geodetic measurement accuracy, and its duration is of the order of months to years. However, details depend on a variety of factors, including the modelling of the constitutive relation near peak stress, coupling of elastic crust to the asthenosphere, and coupling of deformation with pore fluid diffusion. 相似文献
16.
邢台地震前地壳形变异常的可能性物理机制 总被引：4，自引：0，他引：4
将地壳介质视为麦克斯威尔体 ,运用差分法和三维有限元方法 ,探讨了邢台分层地壳结构模型 （含高速体和低速体及深大断裂 ）中深部断裂加速蠕滑时 ,平均应力、水平最大剪应力和地表面垂直位移随时间演化的特征 ,计算结果表明 :（1 ）在地壳中上部 1 1km处 ,深部断裂的加速蠕滑急剧加速了水平最大剪应力的增加速率 ,可达数百倍 ,深部断裂的加速蠕滑是邢台强地震成核过程的开始 ,可实现地壳下部的能量向地壳中上部快速转移 ;（2 ）深部断裂的加速蠕滑引起的地面垂直位移变化与邢台地震震前的地表面垂直位移变化非常一致 .说明邢台地震震前地壳表面垂直方向的位移不仅与岩石的膨胀有关 ,而且可能与地壳内深部断裂的加速蠕滑密切相关 . 相似文献
17.
速率和状态相依赖的摩擦定律是本文采用的重要定律。结合Chester-Higgs摩擦模型和McKenzie-Brune摩擦生热模型,在一维弹簧-滑块-断层近似模型下,利用四阶变步长的Dormand-Prince算法,研究探讨了断层摩擦生热对断层演化的影响。结果表明:与忽略温度影响的情形相比,摩擦生热造成的温度上升可导致断层滑移时刻的略微提前,并伴随着摩擦系数和状态变量的下降,同时也使得断层的滑移量和应力降略有减小,而滑移速率有所增大;另外,在考虑温度影响时,有效正应力和临界滑移距离也会影响断层的演化过程,断层上的有效正应力越大,断层失稳时刻越提前,温度上升越明显;断层的临界滑移距离越大,断层失稳时刻则越迟,温度上升越显著,但当临界滑移距离超过5 cm时,具有不同临界滑移距离的断层,失稳时的温度则基本保持一致。 相似文献