可控力源激发EDA介质中横波分裂现象正演模拟研究

在研究了各向异性介质中波动方程的正演模拟现状的基础上,对波动理论进行了总结,并采用FCT有限差分法对EDA介质中的波动方程进行了数值模拟,得到了EDA介质中横波分裂的波场快照,并对波场特性进行了分析。     

The structure of cool accretion disks in semidetached binaries

We present a qualitative analysis of possible changes in the structure of accretion disks that occur in the transition from hot to cool disks. We suggest that an additional spiral-density wave can exist in the inner parts of the disk, where gas-dynamical perturbations are negligible. We consider the formation of this wave and its parameters. The results of a three-dimensional gas-dynamical simulation of a cool accretion disk are presented; these results confirm the possibility of the formation of a new, “precessional,” spiral wave in the inner regions of a cool accretion disk. Possible observational manifestations of such a wave are discussed.     

起伏地表检波器组合响应

在地形条件复杂、干扰波发育的地区,检波器组合接收可以大大提高资料的信噪比。这种组合就是用多个检波器同时接收地震波作为一个地震道的输入,它主要是利用有效波和干扰波传播方向的不同来压制干扰波。根据检波器组合响应的基本原理,将传统的水平面上检波器组合理论推广到起伏地表条件下,主要讨论了起伏地表检波器面积组合的响应情况,并对比了检波器组合滤波后有效波和干扰波的响应。通过分析可知,在地表倾斜的地区,随着倾斜程度的增大,沿上倾方向传来的干扰波压制程度增大,沿下倾方向传来干扰波压制程度减小。用反演方法对检波器组内距进行了优化,在已知检波器组合方向特性的情况下,得到与之匹配的组内距。数值计算表明,检波器组合滤波后的地震资料,有效波的响应明显高于干扰波的响应,信噪比得到很大提高。     

Peculiarities of spreading of acoustic waves over a shelf with decreasing depth

We analyze experimental data collected in Vityaz Bay of the Sea of Japan during study of the peculiarities of spreading of hydroacoustic waves over a shelf with decreasing depth. We found that the waves propagate over a shelf with depths greater than half of the hydroacoustic wave according to the law of cylindrical divergence with least losses of the wave energy. If the depths are shallower than half of the hydroacoustic wave, they spread along the water-bottom boundary as Rayleigh waves of decaying and undamped types with significant absorption of the wave energy by the bottom.     

Depression and elevation tsunami waves in the framework of the Korteweg–de Vries equation

Although tsunamis in the deep ocean are very long waves of quite small amplitudes, as they propagate shorewards into shallow water, nonlinearity becomes important and the structure of the leading waves depends on the polarity of the incident wave from the deep ocean. In this paper, we use a variable-coefficient Korteweg–de Vries equation to examine this issue, for an initial wave which is either elevation, or depression, or a combination of each. We show that the leading waves can be described by a reduction of the Whitham modulation theory to a solitary wave train. We find that for an initial elevation, the leading waves are elevation solitary waves with an amplitude which varies inversely with the depth, with a pre-factor which is twice the maximum amplitude in the initial wave. By contrast, for an initial depression, the leading wave is a depression rarefaction wave, followed by a solitary wave train whose maximum amplitude of the leading wave is determined by the square root of the mass in the initial wave.     

多道瞬态瑞雷波勘探应用研究

在层状介质中,瑞雷波具有频散特性.瑞雷波波速主要与其穿透深度范围内的介质物理性质有关.利用瑞雷波波速与剪切波波速的相关性可以进行岩土力学参数测试,但传统的瑞雷波勘探方法有一定的局限性.本文发展了多道瞬态瑞雷波勘探技术,从测量仪器选择、观测系统设计、数据采集与处理等方面进行了研究,并在岩土工程勘察和地基加固处理效果评价中取得了良好的应用效果.     

Cliff retreat and sea bed morphology under monochromatic wave forcing: Experimental study

Wave flume experiments have been performed to investigate a sandy cliff recession under monochromatic wave forcing. We varied the wave climate through the wave energy flux F and the surf similarity parameter ξ. The various processes of the cliff erosion cycle are depicted. The sea bed evolution mostly depends on the surf similarity parameter ξ. Steep planar (ξ > 0.7), gentle planar (0.5 < ξ < 0.7) and bared (ξ < 0.5) profiles are observed. We observed different bar dynamics, including steady and unsteady self-sustained oscillating states. Then we analyze the role of the eroded material on the cliff recession rate. We show that the cliff recession rate increases with the wave energy flux. Moreover, for a given wave energy flux, it is larger for a gentle planar profile than for a bared profile. However it is similar for both a bared profile and a steep planar profile. The cliff recession rate is not a monotonic function of the cliff height as the type of bottom profile influences the wave energy at the cliff.     

Visualization of tsunami waves with Amira package

In recent years numerical investigations of tsunami wave propagation have been spurred by the magnitude 9.3 earthquake along the Andaman–Sumatra fault in December, 2004. Visualization of tsunami waves being modeled can yield a much better physical understanding about the manner of wave propagation over realistic seafloor bathymetries. In this paper we will review the basic physics of tsunami wave propagation and illustrate how these waves can be visualized with the Amira visualization package. We have employed both the linear and nonlinear versions of the shallow-water wave equation. We will give various examples illustrating how the files can be loaded by Amira, how the wave-heights of the tsunami waves can be portrayed and viewed with illumination from light sources and how movies can be used to facilitate physical understanding and give important information in the initial stages of wave generation from interaction with the ambient geological surroundings. We will show examples of tsunami waves being modeled in the South China Sea, Yellow Sea and southwest Pacific Ocean near the Solomon Islands. Visualization should be a part of any training program for teaching the public about the potential danger arising from tsunami waves. We propose that interactive visualization with a web-portal would be useful for understanding more complex tsunami wave behavior from solving the 3-D Navier–Stokes equation in the near field.     

Influences of Wave Climate and Sea Level on Shoreline Erosion Rates in the Maryland Chesapeake Bay

We investigated spatial correlations between wave forcing, sea level fluctuations, and shoreline erosion in the Maryland Chesapeake Bay (CB), in an attempt to identify the most important relationships and their spatial patterns. We implemented the Simulating WAves Nearshore (SWAN) model and a parametric wave model from the USEPA Chesapeake Bay Program (CBP) to simulate wave climate in CB from 1985 to 2005. Calibrated sea level simulations from the CBP hydrodynamic model over the same time period were also acquired. The separate and joint statistics of waves and sea level were investigated for the entire CB. Spatial patterns of sea level during the high wave events most important for erosion were dominated by local north-south winds in the upper Bay and by remote coastal forcing in the lower Bay. We combined wave and sea level data sets with estimates of historical shoreline erosion rates and shoreline characteristics compiled by the State of Maryland at two different spatial resolutions to explore the factors affecting erosion. The results show that wave power is the most significant influence on erosion in the Maryland CB, but that many other local factors are also implicated. Marshy shorelines show a more homogeneous, approximately linear relationship between wave power and erosion rates, whereas bank shorelines are more complex. Marshy shorelines appear to erode faster than bank shorelines, for the same wave power and bank height. A new expression for the rate of shoreline erosion is proposed, building on previous work. The proposed new relationship expresses the mass rate of shoreline erosion as a locally linear function of the difference between applied wave power and a threshold wave power, multiplied by a structure function that depends on the ratio of water depth to bank height.     

基于波浪理论的水库地质灾害涌浪数值分析方法

有别于国内现行广泛应用Navie-Stokes方程进行地质灾害涌浪的数值模拟技术,本文采用波浪理论对地质灾害涌浪波进行了分析。地质灾害涌浪波是非周期性波,并且有强烈的非线性,介于中等水波至浅水波之间;可用浅水波模型和Boussinesq模型进行数学描述。本文采用有限差分法的Boussinesq模型,以三峡库区龚家方崩滑体涌浪为例,模拟了涌浪波的传播和爬高问题。该模型能够计算形成涌浪瞬时河面、河面最大波高图、最大流速矢量图、最大爬坡和预警分布图。模拟计算结果与调查结果吻合非常好。这说明基于波浪理论的地质灾害涌浪分析方法精度较高,为涌浪的预测研究提供了一种新的研究方法。     

Waves off Puducherry, Bay of Bengal, during cyclone THANE

We studied the wave characteristics during the very severe cyclonic storm THANE which crossed the east coast of India between Puducherry and Cuddalore based on waves measured at a location in Bay of Bengal at 14 m water depth. Objective of the paper is to document the highest wave height measured in the nearshore waters of east coast of India. On 29 December 2011, cyclone passed within 77–315 km of the wave measurement location with maximum wind speed of 46.3 m/s (90 knots) and resulted in maximum wave height of 8.1 m. Maximum wave height recorded is 0.54 times the water depth, and the ratio of crest height to wave height of the highest wave recorded is 0.65. Maximum value of significant wave height estimated using the parametric wave model for deep-water conditions is 6.4 m, whereas the measured value is 6 m indicating that parametric wave model estimates the wave height reasonably well (within 8 % error) during the cyclone period.     

煤矿反射槽波探测技术研究评述

反射槽波可用于单条巷道内探测巷道两侧和掘进前方一定区域内的断层等异常地质构造。目前该项技术已在我国多数矿井开展过探测试验和工程应用,对采掘危险区治理、工作面布置和采掘方案设计等生产环节起到了重要的指导作用。阐述了反射槽波的处理方法和原理,比较了面对巷道的侧帮和掘进前方2种不同探测区域时,反射槽波数据和处理方法的异同之处,着重对反射槽波的叠加成像、偏移成像以及掘进工作面超前成像3类成像方法的技术原理、适用条件和研究进展进行了梳理和分析,总结了反射槽波在巷道侧帮与掘进前方断层、采空区以及陷落柱探测方面的典型案例。在此基础上提出进一步提高探测能力的改进方向：研究适用于槽波频散性的反褶积方法,有效压缩反射槽波并依据频散速度准确偏移归位,提高成像分辨率;通过极化处理求出槽波的偏振方向,从而减少“画弧”现象;借鉴束偏移技术,选取特定方向的槽波参与成像,提高成像信噪比;研究影响反射槽波信号强弱的地质条件和采集条件,在不增加震源能量的条件下有效增强反射槽波;研制新型震源,提高反射槽波探测应用的安全性和适用性。对反射槽波未来的应用方向进行展望,以期促进反射槽波探测技术发展,为煤矿安全高效开采提供保障。     

Estimation of wave period statistics using numerical coastal wave model

We used field and model wave data to investigate that zero crossing and average wave period distribution follow Gamma distribution. Since Gamma CDF is an infinite power series, further mathematical treatment is difficult. Hence its shape parameter is approximated to the nearest integer to arrive at Erlang distribution. An expression is derived from Erlang distribution to estimate various mean wave periods and significant wave period and validated by relative root mean square (RRMS) error criteria. It is shown by mathematical logic that the significant wave period distribution follows Erlang (or Gamma) distribution and is validated. The average of one-third and one-tenth highest wave periods (T _s ) estimated from Erlang distribution are in accordance with the values computed from recorded buoy and numerical coastal wave model wave period data. The predicted T _s values from coastal wave model wave period data underestimates the values from buoy wave period data.     

综采工作面随采地震的采煤机震源模拟

为了分析以采煤机作为震源接收到的随采地震数据的波场特征,从正演模拟的角度出发,通过将采煤机截割方式及滚筒的受力情况转换为震源力函数的形式,以不同时间不同位置的荷载分布作为震源对波动方程进行加载,采用高阶交错网格有限差分法对波动方程进行求解,得到正演单炮数据。最终,数值模拟得到的随采地震数据显示出,采煤机震源激发的波场中,横波能量占据主导地位,纵波能量较小,且在高频数据中,y分量上有明显的槽波存在,其极化特征显示出该槽波为Love型槽波。最终,模拟数据与实际采集的y分量数据对比表明,二者在波场成分及分布方面具有较高的相似性。     

地震波散射研究回顾与展望

地震波散射是地球物理学中一个非常重要的研究领域,其进展对人们正确认识和了解地球深部的细节及物性具有重大意义,对地球动力学的研究也具有不可忽视的推动作用。这里从地震波散射的理论和方法研究二个方面,对地震波散射研究的进展作评述。首先回顾了地震波散射的基本概念、研究历程及研究的各个方面,对散射理论进行了系统评述,同时对先辈们关于散射波数值模拟的情况进行了总结。     

宽线三维转换波资料处理方法及效果分析

研究了三维转换波资料坐标旋转、面元划分及三维共转换点计算方法,即将每一个转换波共炮点道集内所有地震道进行坐标旋转,旋转后的转换波道集在炮检距、纵横波速度已知的条件下,用迭代方法计算三维转换点的平面坐标,并绘制在平面上.将平面分割为小的面元,凡是转换点在同一面元内的记录道都属于同一共反射点转换波道集,转换点面元大小与纵横波速度比有关.在上述研究的基础上,建立了宽线三维转换波资料处理流程,处理了某油田某地区的宽线转换波资料.     

Nearly perfectly matched layer boundary conditions for operator upscaling of the acoustic wave equation

Acoustic imaging and sensor modeling are processes that require repeated solution of the acoustic wave equation. Solution of the wave equation can be computationally expensive and memory intensive for large simulation domains. One scheme for speeding up solution of the wave equation is the operator-based upscaling method. The algorithm proceeds in two steps. First, the wave equation is solved for fine grid unknowns internal to coarse blocks assuming the coarse blocks do not need to communicate with neighboring blocks in parallel. Second, these fine grid solutions are used to form a new problem which is solved on the coarse grid. Accurate and efficient wave propagation schemes also must avoid artificial reflections off of the computational domain edges. One popular method for preventing artificial reflections is the nearly perfectly matched layer (NPML) method. In this paper, we discuss applying NPML to operator upscaling for the wave equation. We show that although we only apply NPML to the first step of this two step algorithm (directly affecting the fine grid unknowns only), we still see a significant reduction of reflections back into the domain. We describe three numerical experiments (one homogeneous medium experiment and two heterogeneous media examples) in which we validate that the solution of the wave equation exponentially decays in the NPML regions. Numerical experiments of acoustic wave propagation in two dimensions with a reasonable absorbing layer thickness resulted in a maximum pressure reflection of 3–8%. While the coarse grid acceleration is not explicitly damped in our algorithm, the tight coupling between the two steps of the algorithm results in only 0.1–1% of acceleration reflecting back into the computational domain.     

煤矿地质灾害的弹性波探测技术

断层、老窑、陷落柱和煤层缺失等地质异常是煤矿潜在的地质灾害,因地质异常不清造成事故和生产停顿的事,在煤矿时有发生。我们根据弹性波对不同地质体之间密度和波传播速度等物性差异的敏感性,分析了纵波、横波、瑞利波和槽波在地层中的传播特性,研究了弹性波地震探测技术。包括探测仪器研制、资料采集和数据处理技术研究。并应用该技术从地面、井下巷道和工作面侧壁,在许多煤矿进行地质异常探测试验,取得明显效果,为煤矿建井、掘进和开采提供了可靠的地质保障,并为煤矿装备了有力的探测手段。     

地震波多次散射波场的高阶谱统计分析

设计了一个特殊且相对规则的散射界面模型,并利用声波动方程高阶有限差分的方法对其进行正演。通过不断改变模型中散射体的横向尺度来控制多次散射波场的强度和特征,然后结合高阶谱统计分析的方法对所得的多次散射波进行分析,进而可以得到多次散射波频率随散射体横向尺度而变化的一些规律。