Three-Dimensional S-Wave Velocity Structure in Eastern Tibet from Ambient Noise Rayleigh and Love Wave Tomography

We apply ambient noise tomography to continuous three-component broadband seismic data between January 1,2008 and December 31,2008 from the regional networks of 76 stations de-ployed by China Earthquake Administration.Ambient noise cross-correlations were performed to produce the Green's functions of each station-pair.Within the period from 6 to 50 s,Rayleigh and Love wave dispersion curves were measured using the multiple filter analysis method.Then three-dimensional(3-D) S-wave velocity structures from th...     

高分辨率地震及大能量瑞雷波法在采空区探测中的应用

采空区由于原始地层错动、裂缝，地层结构破坏，其地球物理特性也发生了变化。地震波在通过采空区沉降地层时，将会产生同相轴错动，有时会伴生明显的绕射；在地面沉陷区域，层状结构被打破，瑞雷波速度存在明显差异，特别在冒落区和煤柱上方，其速度断面图多呈“V”字型分布。利用高分辨率地震波的识别方法及大能量瑞雷波法“V”字型分布特征进行探测，进而综合分析探测成果，可以十分有效地圈定采空区的赋存状态，精度高，定位准确。     

瑞雷波法在灰岩工程中的应用

瑞雷波勘探技术是一种高新技术,在岩土工程中有广泛的应用前景。本文介绍了瑞雷波原理和特点,并对多道瞬态面波法结合具体的岩溶体探测和第四纪化学沉积钙华层的划分工程实例,探讨了瑞雷波法在解决灰岩工程中的应用效果,以及面波速度映像成图对岩溶体探测起到的全面追索和对比作用。     

岩土工程瑞利波勘探新进展

本文从原理、仪器设备、资料解释和应用四个方面扼要综述了国内外正在发展的瑞利波勘探的三种方法:稳态法、瞬态法和长波微动法。这是瑞利波法推广的最新基础性资料。     

Influence of Uneven Trace Spacing on Rayleigh Wave Dispersion

Rayleigh wave dispersion signals are significant to underground investigation.Tradition-ally,uniformed trace spacing is employed in surface wave surveys.In some cases,however,uneven trace spacing is often encountered because of the limitations of the site condition.In order to study the influence of uneven trace spacing on the dispersion data construction of Rayleigh waves,data acquisi-tion is performed based on a 2.5D field layout with a linear array of geophones fixed and a mobile source.The observation d...     

基阶和高阶瑞雷波频散曲线反演对比分析

通过瑞雷波频散曲线反演,可以建立近地表横波速度模型。瑞雷波频散曲线具有多个模态,一般情况下,基阶模态是具有最大能量的模态。目前对瑞雷波频散曲线的反演大多数是基于基阶模态,对于高阶模态的反演比较少。通过对基阶和高阶瑞雷波频散曲线反演对比分析,认为高阶模态和基阶模态频散曲线反演有比较好的一致性趋势,相对而言高阶模态频散曲线反演的横波速度比基阶要高;高阶和基阶模态能量加权反演,不仅保留了频散曲线基阶模态能量强,勘探深度深的特点,而且对浅层低速层也具有更好的响应,可有效提高反演的精度。     

基于S变换的瑞利面波频散分析

提取面波频散曲线是面波资料处理中最关键的一步。由于时频分析方法的局限,提出了利用S变换进行瑞利面波频散分析的方法,并给出了具体算法。该方法在时间频率域中计算相邻两道面波记录同一频率的时间差,再利用道间距除以该时间差来得到该频率对应的相速度,这样避免了在道间距较大的情况下,传统的相位谱法可能造成相位差的缺陷。通过理论模型和实际资料对该方法进行了验证。结果表明,该方法能够提高瑞利面波频散曲线的提取精度,而且算法简单,具有一定的实用性。     

Effective Dispersion Curve and Pseudo Multimode Dispersion Curves for Rayleigh Wave

The hi-energy bands in the dispersion image are usually interpreted as the true dispersion phase velocities.However,the multiple dispersion modes of Rayleigh wave in layered media stack in space,producing the effective dispersion curve and the pseudo multimode dispersion curves in disper-sion image.The effective dispersion curve has the maximum energy with lower phase velocities than pseudo dispersion phase velocities,and thus is often misunderstood as the fundamental mode.Within the tolerable misfit,the ef...     

非饱和土中Rayleigh波的传播特性分析

基于对非饱和多孔介质的研究成果,考虑孔隙中液相和气相的相互影响,研究了非饱和土地基中Rayleigh波的传播特性。通过非饱和土中固相、液相和气相的质量平衡方程、动量平衡方程和非饱和土有效应力原理,建立了问题的弹性波动方程。通过引入势函数及考虑自由透水（透气）的边界条件,经过理论推导给出了非饱和土中Rayleigh波的弥散特征方程。通过数值算例分析了Rayleigh波的波速和衰减系数随饱和度、频率和固有渗透系数等因素的变化规律。结果表明：不同饱和度下波速随频率和固有渗透系数的变化均是先不变,然后小幅下降,再急剧增加,最后趋于一致;衰减系数在不同饱和度下随频率的增大而增大,随固有渗透系数的增大而先增大后减小。     

时频分析在实测瞬态瑞雷波相速度提取中的应用

时频分析是近年发展起来的一个重要的、新的数学分支,目前已成为国际上极为活跃的研究领域。本文首先分析了瑞雷波的频散特性和传统的参数提取方法的缺陷,然后,利用时频分析的方法对实际资料进行了处理。处理结果表明,应用时频分析方法可以提高瑞雷波速提取的稳定性和可靠性。     

Rayleigh wave group velocity in a spherically symmetric gravitating earth model

Expressions for kinetic energy, elastic potential energy and gravitational potential energy for the spheroidal oscillations of a spherically symmetric, self-gravitating, elastic earth model have been obtained. Some inconsistencies in the expressions given by earlier authors have been pointed out. The principle of equipartition of energy and the Rayleigh principle have been used to derive a formula for Rayleigh wave group velocity in terms of energy integrals. This formula can be used to compute the group velocity without the numerical differentiation implied in its definition     

Propagation of Rayleigh waves in unsaturated porothermoelastic media

Based on the frame of elastic theory for unsaturated porous medium, considering the influence of thermal effect, the propagation characteristics of Rayleigh wave in unsaturated porous media are studied. Firstly, the thermoelastic wave equations for three-phase porous media are established, in which the mass balance equations, generalized Darcy law, momentum balance equations, and generalized non-Fourier heat conduction law are taken into account. Secondly, through theoretical derivation, the dispersion equation of Rayleigh wave for unsaturated porothermoelastic media is given by introducing the potential functions. Finally, the variations of the phase velocity of Rayleigh wave are analyzed with numerical examples. The results show that the thermal conductivity has little effect on the phase velocity of Rayleigh wave. The phase velocity of Rayleigh wave increase with increasing of the thermal expansion coefficient and media temperature.     

瑞雷面波在填海造地强夯检测工程中的应用

瑞雷面波在填海造地强夯效果检测中 ,较常规静力学方法具有成本低、效率高、适宜大面积检测的人工地震勘测方法。本文以漳州后石电厂填海造地的强夯效果检测为例 ,给出瑞雷面波检测方法在强夯效果检测应用的技术途径、技术方案 ,并对检测效果进行分析     

多道瞬态瑞雷波法在探测煤矿采空区中的应用

采空区探测是工程建筑和煤矿生产中亟待解决的问题。常规物探方法在对落后的“房—柱”式开采技术造成的面积较小、埋深较浅的采空区进行探测时存在漏报或误报的情况。根据采空区的地球物理特征,探讨多道瞬态瑞雷波技术的探测机理,并通过勘探实例阐述了该方法在浅层煤矿采空区探测中的实用性和有效性。     

瑞利波测试技术发展概况及其应用

土体剪切波速度的测试是土动力学和地震工程研究中的一项重要内容,也是近年来发展起来的浅层地震勘和对已加固地基进行科学评价的一项新技术。本文阐述了稳态瑞利波和和瞬态波法及剪切波速度反演方法的最新近展,重点综述了瑞利波法测度技术在岩土工程的应用现状。     

人工冻土波速及爆破性的研究

从理论上分析了人工冻土波速与爆破性的关系,进行了冻结砂土、冻结粘土在３个不同温度下（－７℃,－１２℃,－１７℃）的纵波速度、横波速度和冻土爆破性试验．结果表明,纵波速度与变形能系数关联度最大,纵波速度能较好地反映冻土的爆破性．     

瑞雷波法在黄土地区地基检测中的应用

瑞雷波勘探技术是近年来发展起来的一种高新技术 ,在岩土工程中具广泛应用前景。介绍了瑞雷波的特点、原理 ,结合具体的工程实例 ,探讨了多道瞬态瑞雷波勘探法在黄土地区灰土挤密桩复合地基、灰土垫层地基等检测中的一些应用。     

青藏高原东部基于噪声的面波群速度分布特征

通过收集青海、甘肃、四川三省的76个地震台记录的2008年1—12月三分量的连续噪声数据,利用噪声面波层析成像的方法获得了青藏高原东部的面波群速度分布特征。首先采用多重滤波方法提取了1 000多条台站对5～50 s的三分量面波群速度频散曲线,然后将研究区域划分为0.2°×0.2°的网格,利用O ccam方法反演了瑞利波(R-R)和勒夫波(T-T)的群速度分布。反演得到的群速度分布特征与地表地质和构造特征表现出较好的相关性,清晰地揭示了地壳内部的横向速度变化。层析成像的结果显示在短周期(8～20 s)内,拥有较厚的沉积层的四川盆地表现为明显的低速特征,而青藏高原东部则表现为较高的群速度分布特征;随着周期的增加(>20 s),群速度的分布特征呈现出与短周期相反的特性,青藏高原东部下方的速度远远低于四川盆地,这可能与青藏高原东部中、下地壳低速层相关联,同时也意味着研究区域的地壳结构具有明显的横向不均匀性。在群速度分布图上,龙门山不仅是四川盆地与青藏高原的地形和构造分界带,同时也对应着高群速度与低群速度的过渡带。     

S-wave velocity structure of the North China from inversion of Rayleigh wave phase velocity

We constructed the S-wave velocity structure of the crust and uppermost mantle (10–100 km) beneath the North China based on the teleseismic data recorded by 187 portable broadband stations deployed in this region. The traditional two-step inversion scheme was adopted. Firstly, we measured the interstation fundamental Rayleigh wave phase velocity of 10–60 s and imaged the phase velocity distributions using the Tarantola inversion method. Secondly, we inverted the 1-D S-wave velocity structure with a grid spacing of 0.25° × 0.25° and constructed the 3-D S-wave velocity structure of the North China. The 3-D S-wave velocity model provides valuable information about the destruction mechanism and geodynamics of the North China Craton (NCC). The S-wave velocity structures in the northwestern and southwestern sides of the North–South Gravity Lineament (NSGL) are obviously different. The southeastern side is high velocity (high-V) while the northeastern side is low velocity (low-V) at the depth of 60–80 km. The upwelling asthenosphere above the stagnated Pacific plate may cause the destruction of the Eastern Block and form the NSGL. A prominent low-V anomaly exists around Datong from 50 to 100 km, which may due to the upwelling asthenosphere originating from the mantle transition zone beneath the Western Block. The upwelling asthenosphere beneath the Datong may also contribute to the destruction of the Eastern Block. The Zhangjiakou-Penglai fault zone (ZPFZ) may cut through the lithosphere and act as a channel of the upwelling asthenosphere. A noticeable low-V zone also exists in the lower crust and upper mantle lid (30–50 km) beneath the Beijing–Tianjin–Tangshan (BTT) region, which may be caused by the upwelling asthenosphere through the ZPFZ.     

Shear-wave velocity model of the Chukuo fault zone,Southwest Taiwan,from cross correlation of seismic ambient noise

The Chia-Nan (Chiayi-Tainan) area is in the southwestern Taiwan, and is located at the active deformation front of the collision of the Eurasian continental plate and the Philippine Sea plate, which causes complex folds as well as thrust fault systems in the area. The Chukuo fault zone is a boundary between the Western Foothill and the Western Coastal Plain in the Chia-Nan area. The nature of the crustal structure beneath the fault zone, especially the eastern part of the fault zone with mountain topography, has not been well known in detailed due to lack of drilling data as well as its limitation in using other geophysical methods, such as active source survey. In this study, we deployed an array with 11 broadband seismic stations to monitor the seismicity of the Chukuo fault zone. The array has recorded more than 1000 microearthquakes around this area. It provides an opportunity to use P- and S-wave travel time data to investigate the both the crustal P- and S-velocity in the fault zone, however due to the nature of the earthquake distribution, the ray density is relatively low at depth between 0 and 7 km. In addition, the uncertainty of S-wave reading for small earthquake also a limit in building precise S-velocity profile, Thus, we take the advantages of using cross-correlation of seismic ambient noise to investigate crustal S-velocity profile in the Chukuo fault area, especially in the mountain area where crustal faulting is a dominated phenomenon. The results indicate that S-wave velocity in the uppermost crust in the Chukuo fault zone is shown to be slower than previous studies. A low velocity layer exists at depth between 1 and 2 km in the east of the Chukuo Fault. The low S-velocity is related to a highly fractured upper crust due to intensive deformation caused by the orogenic process.