Propagation of Elastic Compressional Waves in a Porous-Fractured Medium Saturated with Immiscible Fluids

Izvestiya, Physics of the Solid Earth - The problem of calculating the reflection and transmission coefficients of elastic P-wave incident from a porous half-space onto a fluid-filled crack is...     

双相各向异性介质中弹性波传播特征研究

随着地震工程和能源地震勘探的深入发展,人们所遇到的地下介质愈来愈复杂．常规的各向异性介质理论或双相各向同性介质理论难以精确描述含流体的各向异性介质,如裂缝性气藏、含水页岩等．本文以Biot双相各向异性介质理论为基础,利用弹性平面波方程,推导出了任意双相各向异性介质中弹性波的Christoffel方程．根据Christoffel方程,计算并分析了频率对双相横向各向同性介质中弹性波的相速度、衰减、双相振幅比和偏振特征的影响．结果表明,在4类波(快纵波、慢纵波、快横波和慢横波)中,频率对慢纵波影响最大;当耗散很大时,快纵波、快横波和慢横波的流固相振幅比值近似为1．对偏振特征分析的结果表明,在双相各向异性介质中,弹性波的固相位移偏振方向与流相位移偏振方向将不再保持同向或反向,而是呈不同大小的夹角．     

有限弹性变形地壳中的地震波

地壳由半无限大的基岩上一层厚度为H^-的表土层组成，入射地震波为垂直的SH波，产生水平地面运动。当浅源大地震发生时，在极震区以外行波传播产生地面运动将使地壳介质有非线性的有限弹性变形。用小参数摄动法使非线性控制方程为线性化的小参数各阶控制方程，得出头两阶线性控制方程的解析解。     

各向异性双相介质弹性波场褶积算法数值模拟

从各向同性介质中波场数值模拟的褶积微分算子法出发,推导出了各向异性双相介质中波场传播数值计算的褶积新算法.将常见的二阶微分Biot波动方程用等效的一阶速度—应力双曲方程表示,其中未知的波场向量包括固相和流体的速度分量和应力分量,由此对方程的时间项使用交错网格差分方法计算,而对空间项则采用褶积微分算法进行求解.对各向异性双相介质在单层介质模型和双层介质模型中的波场特征进行了研究.研究的结果显示,在两层介质分界面上当地震波产生反射时能观测到两类纵波和横波,并且在衰减系数大的介质里慢纵波很难见到.     

固体介质中孤立波的传播及演化特征

由于地球介质中广泛存在断裂、微裂缝等地质现象,实际地震资料中会出现形似孤立波的非线性地震现象。因此,对固体介质中孤立波的研究有利于解释这些非线性地震现象的形成机制。本文基于KdV方程,以雷克子波作为初始条件,采用伸缩子机理构建体力模型,利用有限差分的方法模拟了孤立波的演化过程。理论结果表明,非线性地震纵波可以从雷克子波逐渐演化成孤立波,而且地震波的初始振幅和频散系数对模拟结果也有重要影响。通过与实际资料的对比也能说明这种演化的可能性。同时根据方程系数矩阵中元素带状分布的特征,采用稀疏矩阵的存取方法,可以减小计算内存,提高计算效率。     

大口径有压埋地管道穿越活动断层的非线性分析

基于ABAQUS软件平台,建立穿越断层的管道、有压液体及周围土体的三维有限元模型,分别在静力荷载作用和地震作用下,对不同运动形式断层（走滑断层、正断层、逆断层）中的管道进行模拟,并对管道内有无有压液体进行对比分析。分别得到管道在静力荷载作用下和地震作用下空管道与有压管道的变形特征,将其进行对比分析,得到管道内液体的质量和压力在静力荷载作用及地震荷载作用下对管道的不同影响。结果表明：在静力荷载作用下管道内液体的质量和压力提高了管道的抗变形能力,使管道更安全;而在地震作用下管道内液体的质量和压力削弱了管道的抗变形能力,使管道更容易被破坏。     

Simulation of Medium Wave Propagation in the Magnetosphere

Geomagnetism and Aeronomy - A model of the medium of the ionosphere and magnetosphere, including the distributions of the concentrations and temperatures, collision frequencies, and magnetic field...     

Propagation of Stationary Planetary Waves in the Upper Atmosphere under Different Solar Activity

Numerical modeling of changes in the zonal circulation and amplitudes of stationary planetary waves are performed with an accounting for the impact of solar activity variations on the thermosphere. A thermospheric version of the Middle/Upper Atmosphere Model (MUAM) is used to calculate the circulation in the middle and upper atmosphere at altitudes up to 300 km from the Earth’s surface. Different values of the solar radio emission flux in the thermosphere are specified at a wavelength of 10.7 cm to take into account the solar activity variations. The ionospheric conductivities and their variations in latitude, longitude, and time are taken into account. The calculations are done for the January–February period and the conditions of low, medium, and high solar activity. It was shown that, during high-activity periods, the zonal wind velocities increases at altitudes exceeding 150 km and decreases in the lower layers. The amplitudes of planetary waves at high solar activity with respect to the altitude above 120 km or below 100 km, respectively, are smaller or larger than those at low activity. These differences correspond to the calculated changes in the refractive index of the atmosphere for stationary planetary waves and the Eliassen–Palm flux. Changes in the conditions for the propagation and reflection of stationary planetary waves in the thermosphere may influence the variations in their amplitudes and the atmospheric circulation, including the lower altitudes of the middle atmosphere.     

Propagation of Love Waves in a certain type of heterogeneous layer

Summary Propagation of Love Waves in a layer in which the velocity first decreases with depth, reaches a miniumm at a certain depth and then increases as the depth further increases in studied in this paper.     

Identification Criteria for Sources of T Waves Recorded in French Polynesia

—?From a data set of 150 digital records of T phases from 71 sources obtained on seismometers of the Polynesian Seismic Network, we define a discriminant separating earthquake and explosion sources, which uses the maximum amplitude of recorded ground velocity, measured on its envelope, e _Max (in μm/s), and the duration of the phase measured at 1/3 of maximum amplitude, τ_1/3 (in seconds). Earthquake sources and man-made explosions are effectively separated in a log-log space by the straight line ¶¶log₁₀ e _Max = 4.9 log₁₀τ_1/3 - 4.1 .¶¶Other criteria in both the time and frequency domains fail to reliably separate the populations of the various kinds of events. The application of this technique to analog records of large-scale man-made explosions carried out in the 1960s confirms that it provides an adequate discriminant over 3.5 orders of magnitude of ground velocity.     

Effect of Weak Magnetic Storms on the Propagation of HF Radio Waves

Geomagnetism and Aeronomy - Vertical and oblique sounding data for northeastern Russia have been used to analyze the conditions for the propagation of radio waves during weak geomagnetic storms...     

热弹性P波在有流体夹层介质中的传播问题及其基本特征*

本文作为基础理论研究,讨论了热弹性P波在有流体夹层介质中的传播问题。研究结果表明:热弹性波在流体夹层的传播中,不仅存在反射波、透射波,而且,还伴随有具有相同传播速度的温度波;且其反射系数、透射系数均为复数,并与介质的物性参数及夹层厚度有关。同时指出反射波、透射波的振幅、位相均受介质的物性参数及夹层厚度的影响。此外,还表明夹层中往返震荡的层间波是一系列正传热弹性波和反传热弹性波的叠加。     

Features of Radiation and Propagation of Seismic Waves in the Northern Caucasus: Manifestations in Regional Coda

Based on the Anapa (ANN) seismic station records of ~40 earthquakes (M_W > 3.9) that occurred within ~300 km of the station since 2002 up to the present time, the source parameters and quality factor of the Earth’s crust (Q(f)) and upper mantle are estimated for the S-waves in the 1–8 Hz frequency band. The regional coda analysis techniques which allow separating the effects associated with seismic source (source effects) and with the propagation path of seismic waves (path effects) are employed. The Q-factor estimates are obtained in the form Q(f) = 90 × f 0.7 for the epicentral distances r < 120 km and in the form Q(f) = 90 × f1.0 for r > 120 km. The established Q(f) and source parameters are close to the estimates for Central Japan, which is probably due to the similar tectonic structure of the regions. The shapes of the source parameters are found to be independent of the magnitude of the earthquakes in the magnitude range 3.9–5.6; however, the radiation of the high-frequency components (f > 4–5 Hz) is enhanced with the depth of the source (down to h ~ 60 km). The estimates Q(f) of the quality factor determined from the records by the Sochi, Anapa, and Kislovodsk seismic stations allowed a more accurate determination of the seismic moments and magnitudes of the Caucasian earthquakes. The studies will be continued for obtaining the Q(f) estimates, geometrical spreading functions, and frequency-dependent amplification of seismic waves in the Earth’s crust in the other regions of the Northern Caucasus.     

井间弹性波CT中初至波自动提取转换及后处理优化应用

CT技术在地球物理主要应用中分为电磁波CT和弹性波CT,基于射线追踪理论的弹性波层析成像技术是重要的工程物探方法之一,在工程质量检测、工程勘察等领域得到了广泛的应用。该研究经过实践总结了一整套较为高效的后处理流程,开发了数据预处理软件,使得后处理工作量得到降低,给其他研究人员提供一种处理思路和方法。     

The Influence of 3-D Structure on the Propagation of Seismic Waves Away from Earthquakes

-- The seismic records from significant earthquakes are profoundly affected by 3-D variations in crustal structure both in the source zone itself and in propagation to some distance. Even in structurally complex zones such as Japan and Mexico relatively coherent arrivals are found associated with different classes of propagation paths. The presence of strong lateral variations can disrupt the arrivals, and impose significant variations in propagation characteristics for different directions from the source as illustrated by observations for the 1995 Kobe and 2000 Tottori-ken Seibu earthquakes in western Japan. Such effects can be modelled in 3 dimensions using a hybrid scheme with a pseudospectral representation for horizontal coordinates and finite differences in depth. This arrangement improves parallel implementation by minimising communication costs. For a realistic 3-D model for the structure in western Japan the 3-D simulations to frequencies close to 1 Hz provide a good representation of the observations from subduction zones events such as the 1946 Nankai earthquake and the 2000 Tottori-ken Seibu earthquake. The model can therefore be used to investigate the pattern of ground motion expected for future events e.g., in current seismic gaps.     

山西流体观测井水位与气压相关性分析

分析了山西省流体观测井水位动态特征,利用高阶差分、回归分析方法计算了2008年山西省各观测井水位与气压相关系数,得到了气压系数的背景值,进而对气压干扰因素进行定量化的排除,并对各井的气压系数进行对比分析。结果表明,不同的观测井孔水位受气压影响程度不同,对于某一个观测井孔而言,气压系数及相关系数的变化是有一定规律的。     

楔形空间中圆弧形沉积对平面P波的散射解析解

基于大圆弧假定,利用傅立叶-贝塞尔（Fourier-Bessel）级数波函数展开法,给出了含圆弧形沉积的楔形空间对平面P波的散射解析解。为方便构造地表面引起的散射波场,本文利用2个大圆弧面来模拟地表面,由连续性边界条件建立方程并求解得出该问题的解析解。算例结果表明,楔形空间沉积附近地表的动力响应特征依赖于入射波频率、入射角度、沉积内外介质特性与楔形夹角等因素,且位移放大效应较半空间情况更为显著。