云南地区介质衰减、场地响应及震源参数研究

利用云南区域地震台网2012-2023年的地震波形记录,采用联合反演方法,获得研究区的介质衰减Q值、67个台站的场地响应以及区内ML2.0以上2819次地震的震源参数。结果显示,在三段地震波几何衰减模型基础上,非弹性衰减模型较准确地反映了云南地区构造复杂、地震活动性较强的特征。在研究区67个台站中,场地响应总体上没有出现明显的放大效应,但存在显著的高频衰减现象。在卓越频段1~6Hz,场地放大倍数大多为1~4倍;在10Hz以上高频段,场地的衰减幅度大多在0~95%之间。其中,12个台站的场地响应值在1附近波动;4个台站的场地响应值在低频段接近1,在高频段放大;5个台站的场地响应值整体上略小于1;46个台站出现低频段稍微放大,高频段衰减的现象。各震源参数的相关性分析结果表明,地方性震级与矩震级、地震矩、应力降、视应力及辐射能量均正相关,与拐角频率负相关。滇西漾濞、盈江、芒市地震余震区及滇南红河断裂南段是中小地震应力释放水平相对较高地区,沿金沙江–红河断裂带,尤其是滇南红河断裂带南段沿线则是高应力降地震集中的区域,说明这里的断层可能受到相对较强的构造剪应力作用。

场地响应、震源参数与介质衰减的同时反演

采用Ω平方模型来约束中小地震的震源位移振幅谱,从而实现对震源参数、介质的几何扩散特征、介质的非弹性衰减以及场地响应等参数的同时反演,数值模拟结果表明该方法是可靠的。江苏省苏南地区的几何扩散较好地符合三段衰减统计模型,该地区的品质因子与频率的依赖关系以频率3.0Hz为界分为低频、高频二部分,且均符合指数衰减关系,而全部频率点的品质因子频率依赖关系似乎与四元素流变模型的Q值理论频率特征曲线比较一致。该地区中小地震地震矩对数值与震级ML具有较好的线性关系;地震矩与拐角频率呈现出良好的双对数关系,且该地区的地震应力降与震源半径之间的关系在震源半径小于300m时与圆盘静态破裂模式理论关系较吻合。

衰减性介质中的纵波速度:实验物理模型研究

弹性波速度通常是通过拾取传播脉冲特定特征(如初至波振幅最大值)的旅行时决定的。然而介质的衰减和散射改变了传播波形,从而使确定有意义的速度时出现问题。所以,这样得到的速度不能代表介质固有的波的相速度和群速度。通过实验,从由饱含甘油、未固结、随机充填玻璃珠子和石英砂组成的高衰减介质中得到相速度和群速度。我们的实验结果表明,在200～600kHz的有效频率带内速度的品质因素Q在2～6之间变化。把基本速度与更一般的简单速度估算值作比较。一般情况下,用比较简单的方法能估算出主频率误差为3％的群速度,但与其对应的相速度吻合很差,用第一探测脉冲旅行时得出的波速度(信号速度)与主群速度的差异达到12％。在波速随频率而增加的介质中,初至波速度至多为高频带的相速度提供了一个底界。然而,正如波至时间和传播距离间高质量的线性回归所显示的那样,每一种旅行时拾取方法都是自相一致的。

安徽地区地震波衰减、场地响应及震源新参数的测定

根据安徽数字地震台网7个地震台的143条波形资料,研究了安徽地区的衰减模型和各台站的场地响应。采用三段几何衰减模型拟合,得到了安徽及邻近地区的几何衰减函数,得到安徽地区非弹性衰减Q值随频率f的关系为Q(f)=235.3×f0.616;7个台站的场地响应均无明显的放大效应,这与它们均处于岩石地基相符;并在本地区地震预测研究中尝试使用新参数,进行了初步的应用。

简化的三维TTI介质黏滞纯声波方程及其数值模拟

地球介质普遍具有非弹性和各向异性特征,因此在研究地震波在地下空间传播时应该同时考虑各向异性和黏滞性。在各向异性介质波场模拟、偏移成像和波形反演中,目前主要采用的是伪声波方程,该类方程是在直接将横波速度设置为0的基础上发展的,当介质参数不满足假设条件时容易产生伪横波数值干扰及模拟不稳定。考虑到伪声波方程存在的问题,文中应用泊松算子和有限差分相结合的策略求解高精度的三维TTI介质纯声波方程。同时,考虑到衰减介质对地震波振幅和相位的影响,在各向同性黏滞声波方程的基础上,推导了一种简化的三维TTI介质黏滞纯声波方程,该方程能够模拟纯声波的相位畸变和振幅衰减。应用三维层状模型、TTI楔状体模型和改进的Marmousi模型验证了方法的有效性和适用性。

中国大陆主要地震活动区中小地震震源参数研究

本文利用中国大陆几个主要地震活动区近几年积累的大量M_L≥2.5数字地震观测记录,在分别反演得到13个不同构造研究区域的介质衰减模型、348个台站的场地效应的基础上,自0.1～20 Hz的SH观测波形数据中逐步消除了仪器、噪声、儿何扩散、传播路径的介质衰减、台站场地效应等影响后,恢复了2573次3.0≤M_L≤6.0地震的震源谱,采用ω平方震源模型拟合震源谱后,利用Brune的圆盘模型计算了它们的震源参数,并讨论了中国大陆中小地震的震源特征,比较了中国大陆不同地区的应力降释放水平,综合讨论了地震应力降与震源深度、机制解类型、地震大小等各种因素的关系.研究表明,中国大陆中小地震释放的应力降在0.1～20 MPa之间,绝大多数在10 MPa以下.新疆天山中东段地区、青藏块体东北缘及龙门山断裂带东北缘是高应力降地震集中的区域,表明这里的断层受到相对较强的构造剪应力作用.中小地震释放的应力降随着震级的增大而增大,应力降△σ∝M_0^(3.14),不遵循常数应力降模型.在深度20 km以内,中小地震释放的应力降对深度的依赖不显著,但在20 km以上深度显示出随深度增大而增大的现象.中小地震释放的应力降没有表现出与震源机制类型的相关性.本研究实现了震源参数的准实时计算,丰富了大陆块体内部地震震源定标率关系研究的样本.可以预见,随着中小地震数据的大量产出和积累,这些震源参数的时空分布特征研究将会为地震预测预报研究提供有实际物理意义的依据,得到的介质衰减模型及场地效应等也将对台网日常震级M_L测定所需的量规函数、台站校正值的研究提供重要参考.

青藏高原东缘下地壳流动的地震学证据

在2000年完成的穿过川西高原和四川盆地的深地震测深剖面揭示了川西高原的地壳结构具有地壳增厚（主要是下地壳增厚）、地壳平均速度低等特点，显示地壳的缩短与增厚的碰撞变形特征。根据川西高原上设置各爆炸点的记录截面图共同呈现PmP（莫霍界面反射波）弱能量的特点，推断在川西高原的下地壳介质具有强衰减（Qp=100—300）的性质。利用我国西部地区的宽频带地震台站的面波资料反演青藏高原及其邻区的地壳上地幔S波三维速度结构，在周期T=29．2s和T=42．9s的Rayleigh波群速度分布图上，显示了青藏高原东部（包括川西高原）呈现大范围的低速异常。多方面的结果表明，地震学方法为当前流行的下地壳流动模型提供了深部证据。

宣白承气汤对急性呼吸窘迫综合征大鼠BTLA/HVEM通路及肺功能的影响

目的探究宣白承气汤对急性呼吸窘迫综合征(ARDS)大鼠肺功能及B和T淋巴细胞衰减子(BTLA)/单纯疱疹病毒侵入介质(HVEM)通路的影响。方法60只大鼠,取12只为空白组,其余大鼠通过气管内滴入脂多糖(LPS)造模。将造模大鼠分为模型组、宣白承气汤高、中、低剂量组(22.8、11.4、5.7 g/kg),每组12只。宣白承气汤高、中、低剂量组给予相应的药液,共给药7 d,1次/d。观察大鼠一般状态;血气分析仪测定动脉血中的氧分压(PaO_(2))和二氧化碳分压(PaCO_(2)),计算氧合指数(P/F)和肺泡-动脉血氧分压差[P(A-a)O_(2)];计算肺湿/干比(W/D),苏木素-伊红(HE)染色观察肺部病理学变化;酶联免疫吸附试验(ELISA)检测肺匀浆中肿瘤坏死因子(TNF)-α、白细胞介素(IL)-1β、IL-2、IL-10水平;流式细胞术鉴定大鼠外周血T淋巴细胞亚群比例和BTLA、HVEM在大鼠外周血CD4^(+)和CD8^(+)T细胞表面的表达。结果与空白组相比,模型组精神萎靡,肺体积增大,肺组织结构严重受损;PaO_(2)、P/F、外周血中CD3^(+)、CD4^(+)T比例、CD4^(+)/CD8^(+)比值、肺匀浆中IL-2水平降低,差异有统计学意义(P<0.05),P(A-a)O_(2)、W/D、肺匀浆中TNF-α、IL-1β、IL-10水平、外周血中CD8^(+)T值、CD4^(+)和CD8^(+)T细胞表面BTLA、HVEM表达显著升高(P<0.05);与模型组相比,宣白承气汤高、中剂量组一般状态明显改善,肺组织损伤程度明显减轻,少量炎性细胞浸润;PaO_(2)、P/F、CD3^(+)、CD4^(+)T比例及CD4^(+)/CD8^(+)比值、IL-2、IL-10水平明显升高(P<0.05),P(A-a)O_(2)、W/D比、TNF-α、IL-1β水平、CD8^(+)T值、CD4^(+)和CD8^(+)T细胞表面BTLA、HVEM表达明显降低(P<0.05)。结论宣白承气汤可ARDS大鼠增强T淋巴细胞免疫功能,改善肺损伤;其机制可能与BTLA/HVEM的表达下调有关。

Physical mechanism of seismic attenuation in a two-phase medium

High-frequency seismic attenuation is conventionally attributed to anelastic absorption. In this paper, I present three studies on high-frequency seismic attenuation and propose that the physical mechanism results from the interference of elastic microscopic multiple scattering waves. First, I propose a new theory on wave propagation in a two-phase medium which is based on the concept that the basic unit for wave propagation is a nano- mass point. As a result of the elasticity variations of pore fluid and rock framework, micro multiple scattering waves would emerge at the wavelength of the seismic waves passing through the two-phase medium and their interference and overlap would generate high- frequency seismic attenuation. Second, I present a study of the frequency response of seismic transmitted waves by modeling thin-layers with thicknesses no larger than pore diameters. Results indicate that high-frequency seismic waves attenuate slightly in a near-surface water zone but decay significantly in a near-surface gas zone. Third, I analyze the seismic attenuation characteristics in near-surface water and gas zones using dual-well shots in the Songliao Basin, and demonstrate that the high-frequency seismic waves attenuate slightly in water zones but in gas zones the 160-1600 Hz propagating waves decay significantly. The seismic attenuation characteristics from field observations coincide with the modeling results. Conclusions drawn from these studies theoretically support seismic attenuation recovery.

An analysis of seismic scattering attenuation in a random elastic medium

Seismic attenuation has been inherent media characteristics in which an interesting topic of research, for it reflects the seismic waves propagate. There are many factors that cause seismic wave attenuation, such as geometry attenuation caused by energy dissipating during propagation, friction attenuation by relative sliding among rock grains, and scattering attenuation by rock heterogeneity. In this paper we study P-wave scattering attenuation in a random elastic medium by numerical simulations from a statistical point of view. A random elastic medium model is built based on general stochastic process theory. Then a staggered-grid pseudo-spectral method is used to simulate wave propagation. Scattering attenuation is estimated by the spectral ratio method based on virtual detector records. Random elastic media numerical scatter results with various heterogeneity levels show that the higher heterogeneous levels cause greater scattering attenuation. When the scatter sizes are smaller than a wave length, the larger scatters give a greater attenuation. Finally, we propose a method to evaluate fluid-flow attenuation in porous media. The fluid- flow attenuation is derived from total attenuation and scattering attenuation in random porous media and the attenuation is estimated quantitatively. Results show that in the real seismic frequency range when the heterogeneous scale is about 10^1 meters （less than one wave length）, scattering attenuation is larger than fluid-tlow attenuation in random porous media and scattering attenuation is the main factor of seismic attenuation in real heterogeneous porous media.

Propagation and attenuation of P-waves in patchy saturated porous media

We establish a patchy saturation model and derive the seismic wave equations for patchy saturated porous media on the basis of Biot＇s equations and Johnson＇s bulk modulus. We solve the equations, obtain the attenuation coefficients, and analyze the characteristics of wave attenuation in the seismic frequency range. The results suggest that seismic waves show attenuation and dispersion in partially saturated rocks in the low frequency range. With frequency increasing, attenuation increases. The attenuation of P-waves of the second kind is more pronounced in agreement with Biot＇s theory. We also study the effect of porosity, saturation, and inner sphere radius on the attenuation of the P-waves of the first kind and find that attenuation increases with increasing frequency and porosity, and decreases with increasing frequency and degree of saturation. As for the inner sphere radius, wave attenuation is initially increasing with increasing frequency and inner sphere radius less than half the outer radius. Subsequently, wave attenuation decreases with increasing frequency and inner sphere radius is higher than half the outer sphere radius.

CATV电缆传输特性探讨

当今我国有线电视网络正经历从单向传输向双向传输,从单一同轴电缆传输向HFC网络传输的过渡。使用的传输频带也普遍向550MHz系统乃至750MHz系统过渡。技术上的进步,网络传输水平的提高,对用于CATV系统的同轴电缆的技术特性提出了更高的要求。本文拟就CATV电缆的传输特性,着重从使用的角度提出一些看法。

黏声方程Q值反射波反演

地震波在非弹性介质中的衰减效应常用品质因子Q度量.相对准确的Q模型对提高强衰减介质中地震波成像的质量至关重要.本文提出了黏声介质反射波形反演(QRWI)方法来重建地下宏观Q模型.在缺乏大偏移距和低频地震数据时,该方法以黏声波方程为波场传播引擎,利用反射波核函数对模型中深部的敏感性去提取背景Q值.当速度高、低波数成分均已知时,基于波形拟合的QRWI可以获得较高分辨率的反演结果.由于地下介质速度的高波数扰动很难准确估计,本文通过引入峰值频移目标函数,极大地降低了QRWI对速度高波数成分的依赖.理论合成数据实验结果表明,本文方法反演得到的宏观Q模型可以满足衰减补偿逆时偏移成像的要求.

P-wave attenuation anisotropy in TI media and its application in fracture parameters inversion

The existence of aligned fractures in fluid-saturated rocks leads to obvious attenuation anisotropy and velocity anisotropy. Attenuation anisotropy analysis can be applied to estimate fracture density and scale, which provide important information for reservoir identification. This paper derives P-wave attenuation anisotropy in the ATI media where the symmetry axis is in the arbitrary direction theoretically and modifies the spectral ratio method to measure attenuation anisotropy in the ATI media, thus avoiding a large measurement error when applied to wide azimuth or full azimuth data. Fracture dip and azimuth can be estimated through attenuation anisotropy analysis. For small-scale fractures, fracture scale and fracture density can be determined with enhanced convergence if velocity and attenuation information are both used. We also apply the modified spectralratio method to microseismic field data from an oilfield in East China and extract the fracture dip through attenuation anisotropy analysis. The result agrees with the microseismie monitoring.

Acoustic parameters inversion and sediment properties in the Yellow River reservoir

The physical properties of silt in river reservoirs are important to river dynamics. Unfortunately, traditional techniques yield insufficient data. Based on porous media acoustic theory, we invert the acoustic parameters for the top river-bottom sediments. An explicit form of the acoustic reflection coefficient at the water-sediment interface is derived based on Biot＇s theory. The choice of parameters in the Blot model is discussed and the relation between acoustic and geological parameters is studied, including that between the reflection coefficient and porosity and the attenuation coefficient and permeability. The attenuation coefficient of the sound wave in the sediments is obtained by analyzing the shift of the signal frequency. The acoustic reflection coefficient at the water-sediment interface is extracted from the sonar signal. Thus, an inversion method of the physical parameters of the river- bottom surface sediments is proposed. The results of an experiment at the Sanmenxia reservoir suggest that the estimated grain size is close to the actual data. This demonstrates the ability of the proposed method to determine the physical parameters of sediments and estimate the grain size.

A patchy-saturated rock physics model for tight sandstone based on microscopic pore structures

The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.

Sensors for control of water transparency in optical and microwave ranges

In the face of deteriorating environmental conditions in the world,water quality control is an urgent task.It can be solved by creating sensors with high accuracy and low cost,which requires the development of fundamentally new radiophysical methods that take advantage of the optical,microwave and millimeter wavelengths that have a significantly greater sensitivity to low concentrations of pollutants and a lower inertia.The article presents prototypes of measuring cells of the microwave and optical ranges as well as the results of an experimental study of water of various degrees of pollution with their help.The results show that the use of the highly sensitive method of capillary-waveguide resonance makes it possible to detect the presence of micro impurities in water with concentrations up to0.1%and to identify water even from sources of various natural origins.In addition,the use of measurements at several frequencies in the optical range will make it possible to solve the problem of creating water control sensors with high sensitivity to pollution and low cost.It can be concluded that the possibility of complex use of multiwave sensors(optical,infrared and microwave ranges)allows to increase the sensitivity and reliability of water quality assessment.

B→ X8γ, X8l＋l- Decays and Constraints on Mass Insertion Parameters in MSSM

In this paper, we study the upper bounds on the mass insertion parameters （δAB^q）ij in the minimal super symmetric standard model. We found that the information from the measured branching ratio of B→ X8γ, X8l＋l- decay can help us to improve the upper bounds on the mass insertions parameters （δAB^u,d）3j,i3 Some regions allowed by the data of Br（B→ X8γ） are excluded by the requirement of an SM-like C7γ （rnb） imposedby the data of Br（B→ X8γ, X8l＋l- ）.

同轴电缆外导体结构与衰减分析

基站同轴电缆的金属衰减在电缆总衰减中占主导地位，电缆外导体的结构、形状对电缆衰减有很大影响，本文将对电缆外导体形状对电缆衰减的影响建立新的模型进行计算。

Wave dispersion and attenuation in viscoelastic isotropic media containing multiphase flow and its application

In this paper, we introduce the complex modulus to express the viscoelasticity of a medium. According to the correspondence principle, the Biot-Squirt （BISQ） equations in the steady-state case are presented for the space-frequency domain described by solid displacements and fluid pressure in a homogeneous viscoelastic medium. The effective bulk modulus of a multiphase flow is computed by the Voigt formula, and the characteristic squirt-flow length is revised for the gas-included case. We then build a viscoelastic BISQ model containing a multiphase flow. Through using this model, wave dispersion and attenuation are studied in a medium with low porosity and low permeability. Furthermore, this model is applied to observed interwell seismic data. Analysis of these data reveals that the viscoelastic parameter tan6 is not a constant. Thus, we present a linear frequen- cy-dependent function in the interwell seismic frequency range to express tanG. This improves the fit between the observed data and theoretical results.