共查询到18条相似文献,搜索用时 984 毫秒
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针对地震勘探资料湮没在随机噪声中的微弱同相轴问题提出基于混沌理论的混沌振子检测算法. 利用修正的Duffing_Holmes方程建立检测微弱同相轴的混沌振子系统,之后经过对同相轴的扫描处理,构成新子波等时间间隔序列W(t),与此同时对随机噪声也进行相同的截断. 截断的随机噪声在混沌振子系统中可以具有与周期信号相同的表现;经过大量仿真实验确定出满足通常地震勘探子波延续时间的使混沌振子检测子波不呈现周期相态的随机噪声截断时间范围. 选用与松辽盆地T1、T2反射层类似的子波函数并构成待检微弱周期信号,经过MATLAB仿真试验成功地检测出该弱信号,信噪比达到约-103dB. 相似文献
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在远程检测地下核爆炸的唯一途径是依据其产生的地震信号。正因为这个原因,为验证“全面禁止核试验”情况提供数据而建立的国际监测系统(IMS)还得包含地震台站网。然而,即使监测到了地下核爆信号,也不可能准确无误地辨别出来。该监测系统旨在提供可鉴别出明显是天然扰动的数据和可识别出极有可能是地下核试验的数据。如果检测到可疑扰动,禁止核试验条约的缔约国就可要求这个被怀疑进行核试验的国家允许国际调查组织进入震中区进行现场视察,来核实其是否确实进行了核试验。 相似文献
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利用加速度计进行近钻头井斜动态测量时,钻具的高速旋转,井下强振动、强冲击环境给重力加速度测量带来极大干扰,如何从干扰噪声中有效提取重力加速度信号对于提高井斜角和工具面角的测量精度至关重要.根据重力加速度径向和切向分量为周期性信号,轴向分量为近似直流信号,离心加速度为缓慢变化信号,振动和冲击加速度为随机信号的特征,提出一种基于互相关检测的重力加速度信号提取方法,选择径向或切向磁力计信号作为参考信号.利用相关检测方法分别对仿真数据、实验室旋转测试数据和振动测试数据进行处理,并计算了井斜角和工具面角,结果表明相关检测方法可以有效提取重力加速度信号,基于MEMS加速度计的井斜角测量精度优于0.5°,工具面角变化连续平滑,满足井斜动态测量需求.通过进一步开展实际钻井环境测试,该方法有望应用于近钻头地质导向系统或旋转导向钻井系统等需要近钻头井斜动态测量的场合. 相似文献
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强随机噪声干扰是导致地震勘探资料低信噪比的主要原因,如何在强随机噪声干扰下获取有效的信息是值得关注的问题.Duffing振子混沌系统是一个非线性的动力学系统,其对强随机噪声具有免疫能力,而对特定的周期性信号具有敏感性.本文提出一种基于Duffing振子混沌系统的速度分析方法.对CMP道集按照时距曲线关系进行移动窗口截取,将所截取的信号构建为待测信号加入Duffing振子混沌系统,通过相图网格分割方法(GPM)判断系统状态的改变,从而在强随机噪声背景下获得高分辨率的速度谱.理论模型和实际资料的处理结果表明,与传统的水平叠加速度分析方法相比,本方法能够在强随机噪声背景下获得更准确的速度分析结果. 相似文献
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针对地震勘探资料中存在加性强随机噪声干扰,已经提出用混沌振子系统处理的方法技术.为完善该方法,需要研究诸如地震勘探同相轴完整程度、组成同相轴的地震子波变化等对系统检测效果的影响.本文以Ricker子波模拟地震子波,研究Ricker子波视主频变化的相应检测效果.研究结果:随着Ricker子波视主频的升高,检测SNR逐渐变差,在高频部分SNR的变化明显比低频部分缓慢;在通常地震勘探频率范围内,混沌振子系统检测SNR有可能部分补偿由于地震波传播引起的幅度降低;为检测由畸变子波构成的同相轴提供一定的可能. 相似文献
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The classical theory of detection using the Neyman-Pearson principle is applied to stratosphere-troposphere (ST) radar signals. It is extended to provide information regarding the detection of weak signals which complements the detectability method usually employed in ST radar studies. It is shown that for ST radar signals of low amplitude and a detectability around 3 (a value commonly invoked in literature), the probability of detection is about equal to the probability of false alarm. The question of threshold detectability is also discussed.Spectral moments errors are evaluated by a method which is an extension of the analytical method of estimation developed by Miller and Rochwarger and the results compared to other statistical and analytical models. As already known, three factors can affect the error on the estimated parameters: the signal-to-noise ratio, the spectral width and the incoherent integration number. For high signal-to-noise ratios, analytical results are in good agreement with Barrick’s and Denenberg’s theoretical models and with Yamamoto’s statistical one. For low signal-to-noise ratios, the spectral parameters are more sensitive to the selected model but overall variability is similar. 相似文献
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A. S. Cherepantsev 《Izvestiya Physics of the Solid Earth》2008,44(11):883-897
Observations of a complex of geophysical fields sensitive to deformation processes in the Earth’s crust point to the presence of components of different origins in their time variations. The variations contain not only regular components (seasonal, tidal, anthropogenic, and others) but also random and chaotic components. The chaotic component can be related to variations in the stress-strain state, as was shown in [Smirnov et al., 2005]. Some main properties of the behavior of the chaotic component can be determined on the basis of ideas of nonlinear dynamics. A method of extracting such a “dynamic” component in the process studied requires that its inherent properties be taken into account. This paper develops a method for separating components of a dynamic system from the superimposed component of an external process using invariant properties of the system. The applicability and effectiveness of the method is demonstrated by comparing model calculations with the use of a smoothing moving window of a variable width and real geophysical data. 相似文献
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提出了用局部指数标架小波束进行角度域分解的方法,解决了局部余弦基和局部正弦基缺乏单一方向性的问题.局部指数标架由局部余弦基和局部正弦基线性组合而成,是冗余度为2的紧标架.利用局部余弦变换和局部正弦变换的快速算法,能使基于局部指数标架进行方向照明分析的计算效率较常用的局部倾斜叠加和Gabor-Daubechies标架等方法具有更为明显的优势.通过计算二维SEG/EAGE模型和SIGSBEE模型的方向照明图以及采集系统倾角响应图证实了本文方法的有效性.该方法的高效性使其在三维模型的方向照明分析和大规模的工业应用中具有广阔前景. 相似文献
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GUO Yang XU Jiajun LIN Chen JIN Xing YAO Huajian YANG Hongfeng CAI Huiteng 《中国地震研究》2019,33(2):265-275
112 short-period seismographs were set up in the 400km2 area of Pingtan Island and its surrounding areas in Fujian. The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording. The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave''s first arrival time data, and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve, which can provide initial model for subsequent 3-D imaging. The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection, which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island. 相似文献
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S. H. Ju 《地震工程与结构动力学》2003,32(9):1431-1442
This paper discusses how to use the three‐dimensional (3D) time‐domain finite‐element method incorporating the least‐squares method to calculate the equivalent foundation mass, damping and stiffness matrices. Numerical simulations indicate that the accuracy of these equivalent matrices is acceptable when the applied harmonic force of 1+sine is used. Moreover, the accuracy of the least‐squares method using the 1+sine force is not sensitive to the first time step for inclusion of data. Since the finite‐element method can model problems flexibly, the equivalent mass, damping and stiffness matrices of very complicated soil profiles and foundations can be established without difficulty using this least‐squares method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献