含泥质低孔渗各向异性黏弹性介质中的波频散和衰减研究   总被引：8，自引：5，他引：3       下载免费PDF全文

聂建新  杨顶辉  巴晶 《地球物理学报》2010,53(2):385-392

本文定义了各向异性黏弹性参数修正因子,并将其引入到黏弹性模型中以体现泥质含量对黏弹性机制的影响,同时将波传播过程中孔隙介质骨架黏弹性力学机制与两种孔隙流体流动力学机制（Biot流动和喷射流动机制）有机地统一起来处理,从而给出了描述含泥质低孔渗孔隙各向异性介质中波传播规律的黏弹性Biot/squirt (BISQ)模型.数值计算结果表明,入射波的方位角、各向异性渗透率以及泥质含量等对含流体复杂孔隙介质中波频散和衰减的影响具有显著的方位各向异性特征,在低频范围内（地震波勘探频率）黏弹性力学机制对波传播能量的衰减起主导作用.  相似文献   

巴颜喀拉块体周缘几次强震对甘肃地区地震形势的影响   总被引：1，自引：0，他引：1  

杨兴悦  陈连旺  杨立明  李玉江 《地震》2013,33(3)

以青藏高原为目标,采用黏弹性体本构关系建立3D有限元模型,模拟了在印度板块持续向北推进、挤压下,巴颜喀拉块体周缘强震对邻近地区的影响.通过降低强震发生位置处单元弹性模量的方法模拟了2001年昆仑山口西MS8.1、2008年汶川MS8.0、2010年玉树MS7.1地震,计算了发生这3次MS7.0以上强震后50年内每5年的黏弹性调整过程,讨论了3次强震对祁连地震带及甘东南地区地震形势的影响,尝试开展依据区域应力调整特征判定未来强震危险区的探索试验.  相似文献   

昆仑山M_s 8.1级地震震后变形场数值模拟与成因机理探讨   总被引：2，自引：0，他引：2       下载免费PDF全文

邵志刚  傅容珊  薛霆虓  黄建华 《地球物理学报》2008,51(3):805-816

2001年11月14日,在青海和新疆交界处发生了昆仑山M_s8.1级强烈地震,GPS后观测显示,此次地震震后形变不仅在断裂南北两侧存在很大的差异,而且在短时间调整后断裂南北两侧表现为同向运动.本文以观测的地震形变为约束,通过有限元数值模拟分析昆仑山地震震后形变的物理机制.建立有关的有限元虚功方程,通过有限元数值方法模拟震后形变,从理论上分析介质的非均匀性、黏滞性松弛、流体调整对震后形变的影响.采用网格搜索确定昆仑断裂南北两侧下地壳的黏滞系数分别为5.0×10¹⁷Pa·s, 9.0×10¹⁸Pa·s左右,正是这十余倍的差异引起了断裂两侧震后形变的非对称性和同向运动,这一差异既是长期地质作用的结果,又是现代地球动力学环境的决定因素之一.通过数值模拟定性讨论了断裂北侧地表形变在震后短期内的调整,对于靠近断裂附近的测点可能是黏弹性松弛和孔隙流体调整共同作用的结果,所以在分析短期震后形变时综合考虑黏弹松弛和孔隙流体调整是很有必要的.  相似文献   

用于零偏移距VSP资料的自适应波形反演方法研究   总被引：1，自引：1，他引：0       下载免费PDF全文

高静怀  汪超  赵伟 《地球物理学报》2009,52(12):3091-3100

提出一种利用零偏移距VSP资料初至下行波(即直达波)反演介质品质因子Q及层速度V等参数的方法, 称为自适应时域波形反演法(ATWI). 为了充分地利用有效信息, 该方法根据实际VSP资料的信噪比及直达波与上行波干涉的程度,自适应最大限度地选取未受干扰的初至波片段,并用该片段构造目标函数; 通过恰当地构造数据加权矩阵提高目标函数对Q值变化的敏感性;为克服非线性反演的病态问题,采用近来发展的乘性正则化方法,并通过约束条件限制待求参数的取值范围;文中推导出了雅可比矩阵各元素的解析表达式,从而减小了反问题的计算量.合成数据反演结果表明,与谱比值法和子波包络峰值瞬时频率法相比较,ATWI法受上行波影响相对较小、抗噪性能更强.实际资料算例进一步证明了ATWI方法的有效性.  相似文献   

The Chi-Chi 1999 earthquake: Correlation between the spatio-temporal distribution of aftershocks and viscoelastic stress changes     

Chiou-Fen Shieh  Shyh-Yang Sheu 《Journal of Geodynamics》2008,45(4-5):208-216

The Chi-Chi 1999 (M_L = 7.3) earthquake generated a large number of aftershocks in the vicinity of the rupture plane. The spatial-temporal distribution of these aftershocks was recorded with high precision and thus provided a unique possibility to study whether the correlation between aftershocks and stress changes are primary due to coseismically induced stress changes (static), or whether stress relaxation processes (viscoelastic) in the lower crust contribute significantly to this correlation. From our analysis of a 3D finite element model simulating the viscoelastic stress changes due to the coseismic displacement and tectonic loading we found that the aftershocks are highly correlated with the stress variations (static and viscoelastic) caused by the main shock. Although we found that the correlation between seismicity rate changes and viscoelastic stress fluctuation is slightly better than that of the static stress changes, these differences can only be identified well in the lower crust. As a result, it is reasonable to conclude that static stress changes are the key mechanism for triggering early and shallow aftershocks in the upper crust. It is reasonable to infer that the viscoelastic relaxation in the lower crust does affect the occurrence of early aftershocks in the deep crust, but it does not significantly affect the shallow aftershocks. However, the stress changes induced from the lower crust gradually transfer to the upper crust and may influence the occurrence of aftershocks after a longer time period (>four Maxwell times).  相似文献   

利用GPS观测的时间序列资料反演地壳地幔黏性结构   总被引：12，自引：3，他引：9       下载免费PDF全文

朱守彪  蔡永恩 《地球物理学报》2006,49(3):771-777

地球介质的黏度是地球动力学研究中的重要参数. 在考虑震后震源区介质物性变化的情况下,本文提出利用GPS观测的时间序列资料反演地壳、地幔黏度的方法. 计算中,将遗传算法与Marquardt法相结合,利用遗传算法搜索结果作为Marquardt法反演的初始模型,运用微扰法形成Jacobian矩阵. 根据余震分布及地震波速度变化确定震源区的范围及介质的物性变化情况,利用黏弹性有限单元模型（Maxwell体）及台湾集集地震后GPS观测的时间序列数据,反演了台湾地区地壳、地幔的黏性系数. 反演计算及数值实验表明,该方法反演黏度的效率高,稳定性好. 反演结果初步显示台湾地区的地壳、地幔的黏度分别为12×1018Pa·s和36×1019 Pa·s.  相似文献   

Axisymmetric viscoelastic response of flexible pipes in time domain     

《Applied Ocean Research》2016

The challenges for determining the mechanical behavior of flexible pipes mainly arise from highly non-linear geometrical and material properties and complex contact interaction conditions between and within layers components. This paper develops an innovative model to investigate the linear viscoelastic behavior of flexible pipes under axisymmetric loads in time domain. The model is derived from an equivalent linear elastic axisymmetric model by invoking the elastic-viscoelastic correspondence principle. Analytical formulations that describe the behavior of the metallic helical layers based on a combination of differential geometry concepts and Clebsch–Kirchhoff equilibrium equations for initially curved slender elastic rods are presented. The elastic response of the homogenous polymeric cylindrical layers is also presented. The assemblage of both types of governing algebraic equations that approximate analytical solutions for force and moment distributions, deformations in each layer, as well as contact pressure between near layers, taking time-dependent characteristics of polymeric layers into account are provided and it is clear that the relationship between axial force and elongation is non-linear and encompasses a hysteretic response. Besides, the creep behavior in axial direction can also be found. Some insights into the differences in the behavior for several loading conditions are discussed by considering variable frequencies.  相似文献   

Strength modelling in stiffened FRP structures with viscoelastic inserts for ocean structures     

J. I. R. Blake  R. A. Shenoi  J. House  T. Turton 《Ocean Engineering》2002,29(8):849-869

The purpose of this paper is to investigate the static structural response of a new type of composite stiffener containing a viscoelastic insert. The introduction of this material has proven benefits in terms of noise and vibration attenuation across the joint. House, 1997 describes the use of this material in sonar dome/hull connections — equipment sensitive to noise and vibration. Structural stiffeners incorporating this material would have positive implications for not only marine and ocean structures but for structural applications in general. The effects of introducing this new material on the structural response of the joint are numerically examined by using a progressive damage model. Application of this method allows the initiation and progression of failure and ultimate failure load to be predicted. Experimental results show good qualitative and quantitative agreement with the predictive damage model.  相似文献   

利用同震和震后位移数据联合反演2011年日本MW9.0地震同震断层滑动     

陈伟  刘泰  佘雅文  付广裕 《地震》2021,41(4):121-135

基于黏弹性球体位错理论, 联合陆地和海底同震GPS数据以及日本本岛330个陆地GPS站点5~10年的震后数据, 反演了日本M_W9.0地震的断层滑动模型, 提升了断层滑动分布在细节上的合理性。 首先, 基于日本本岛330个陆地GPS站点震前2年和震后10年的连续观测数据, 获取了日本M_W9.0地震震后5~10年的年平均位移, 该时段的位移几乎完全由地幔黏弹性松弛效应引起; 接着, 利用黏弹性球体位错理论对震后5~10年的位移进行反复拟合, 确定了日本M_W9.0地震震源及周边地区的地幔黏滞性系数最优解(9.0×10¹⁸ Pa·s)。 然后, 联合同震和震后位移数据, 引入黏弹性位错格林函数, 反演了2011年日本M_W9.0地震的断层滑动分布。 结果表明, 该地震同震破裂的最大值达到了62.72 m, 同震滑动的总地震矩为4.48×10²² Nm, 相应的矩震级为M_W9.03。 由于黏弹性松弛效应引起的震后位移中包含了同震破裂的信息, 基于黏弹性球体地震位错理论, 联合同震和震后位移数据反演断层同震破裂, 有效提高了日本M_W9.0地震断层滑动分布的可靠性。 最后, 本文提出的反演方法为同震观测结果缺乏的大地震震后科考提供了理论支撑: 在大地震发生之后, 即使在同震期间没有足够的观测数据, 也可以在震后通过对震源区的加密观测积累的震后数据, 使用本文提出的反演方法优化同震断层滑动模型。  相似文献   

Shear stress on the base of a lithospheric plate     

Jay Melosh 《Pure and Applied Geophysics》1977,115(1-2):429-439

This paper is a review of the theoretical and observational evidence bearing on the magnitude of the shear stress which acts on the base of a lithospheric plate. Estimates based on the viscosity of the upper mantle do not yield useful limits. Arguments based on the thermal stability of the upper mantle indicate that the basal shear stress is no larger than a few bars. An indirect measurement of the rheology and shear stress can be made by studying the diffusion of stress and displacement following a large decoupling earthquake. When applied to the 1965 Rat Island Earthquake, this method yields a basal shear stress of about 2 bars. These results indicate that for small plates the forces produced by basal shear stress are probably small in comparison with forces acting on plate boundaries. To a first approximation, the smaller plates act as if they were decoupled from the mantle below. These stress estimates lead to a model in which the motion of the smaller lithospheric plates is governed almost entirely by the forces acting on their edges. Forces due to basal shear stress may be comparable to forces acting on the edges of large lithospheric plates. Thus, complete decoupling may not be a good approximation for such plates.  相似文献