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The depth to soil–bedrock interface, which is one of the major parameters in the site response analysis, has been often investigated by surface-wave tests. The round-robin tests for a surface-wave method in Korea revealed that a long measurement array in surface-wave tests is not appropriate in locating soil–bedrock interface. In this paper, for the improved profiling of depth to soil–bedrock interface in 2-D image, short measurement array was introduced for the beamforming technique, which is a robust array processing technique adopted in a long-array format for stiffness profiling. Numerical simulation and field applications of the short-array beamforming technique indicate that the method is valid even for surface wave propagation with mode-related complexity. Depth to soil–bedrock interface and shear-wave velocity profiles determined by the short-array beamforming technique were in good agreement with layer stratifications of boring logs, resistivity map, shear-wave velocity profiles of downhole tests and CAP-SASW tests. 相似文献
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针对空时二维滤波器结构,提出了修正两步最小均方波束形成算法,通过修正每次迭代运算中的期望阵列响应幅度和方向矩阵,显著地减少了矩阵运算量,达到快速准确求解期望方向图的相位和相应权矢量的目的。该算法在不改变天线阵元数的情况下,比传统空域滤波增加了时域处理维数,提高了波束形成质量,并利用了期望方向图相位的随机性,通过迭代更新期望方向图的相位和相应权矢量,实现了方向图的旁瓣控制,理论上可以形成任意控制的旁瓣波束,满足不同应用场合的需求。经计算机仿真实验,算法可以很好的收敛到期望的方向图,验证了该算法的有效性。该算法可广泛应用于多天线的GNSS导航接收机或抗干扰接收机中,在提高接收机在复杂环境下的可用性和灵敏度上具有重要的意义。 相似文献
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Acoustic signal parameter estimation is important for diverse marine geodesy surveys and several other applications. However, the received signal from a far-field target characterized by planar wavefront propagation is frequently affected by strong nearby interfering signals. Their presence deteriorates the performance of direction-of-arrival (DOA) estimation for far-field target. In order to enhance the reception of signal from far-field target, the near-field/far-field (NFFF) beamformer is proposed. Such a beamformer optimizes beam pattern for far-field detection by maximizing beamformer output in the direction of the far-field target with the imposed condition to eliminate interfering signals generated in near-field locations. As the interference suppression only occurs at the position of near-field interference, a possible blind zone for far-field detection in conventional methods is not created. The NFFF beamformer is applicable for coherent signals and the scenario with multi interferences. For stationary situation where interferers locations are fixed, the NFFF beamformer computations do not require time updates with associated computational load. Furthermore the proposed method can be extended to several new situations such as acoustic monitoring performed from a stationary platform subjected to water currents, waves, winds and other variables, all of them generating nearby interferences and also to different array configurations including 2D and 3D arrays. 相似文献
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聚束滤波方法的基本原理,包括信号与噪音模型、设计准则和所获得的聚束滤波器．本文所用的自适应聚束滤波器是根据具有参数化的动校正量、振幅及相位随偏移距变化（ＭＶＯ、ＡＶＯ及ＰＶＯ）的一次反射和多次反射信号模型而设计的．但在实际应用中ＰＶＯ通常不能得到证实．结果分析能为进一步的从ＡＶＯ及ＰＶＯ获取岩石类型信息的专题研究提供资料．人工合成资料的例子给出了参数化的自适应聚束滤波的实施细节和所设计滤波器的响应特性．实际资料的例子表明数据自适应聚束滤波在叠前共中点道集地震多次波消除上比Ｒａｄｏｎ变换方法更灵活、有效．类似于其它叠前处理过程,自适应聚束滤波的优越性在信噪比较高的资料上体现得最为明显． 相似文献
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作为近地表横波速度结构成像的主要手段之一,面波多道分析法的正问题研究对现场观测系统设计及后续反演计算具有重要意义.目前面波频散曲线的正演主要分为两类:一是对水平层状介质中面波的本征值问题进行求解,该类方法计算效率高但较难考虑地下介质在横向上的不均匀性;二是基于波动方程的全波场模拟,该类方法在理论上可考虑任意复杂的地质模型但计算成本相对较高.本文基于振幅归一化加权的聚束分析,提出了一种适用于横向非均匀介质模型的多道瑞雷波频散曲线正演方法.首先,基于聚束分析的计算公式推导得到了经振幅归一化加权后输出功率谱中相速度与局部相速度之间的关系,然后通过黄金分割极值搜索算法计算得到了多道瑞雷波数据的理论频散曲线.数值分析结果表明,该算法能够快速地实现横向非均匀介质中多道瑞雷波频散曲线的正演计算,所求取的频散曲线与采用二维弹性波时间域有限差分模拟分析得到的结果误差较小,这在一定程度上说明了该计算方法的可靠性,从而可为面波多道分析法中的观测系统快速优化设计以及横向非均匀介质中频散曲线的反演解释提供理论支撑. 相似文献
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地震勘探中,针对目的层地震数据信噪比较低情况,为改善信噪比,本文提出一种基于接收阵列的时域地震波束形成方法(TSBBRA).该方法的理论依据是波束形成原理,文中通过对相控震源激发定向地震波场的分析,提出在反射地震勘探中,在信号接收端同样能生成定向地震波的思路.具体地,论文给出在地震数据集上先对单炮记录分组,再对组内记录时域内延时、叠加,生成对应定向地震波场的地震记录的方法.TSBBRA方法适于杂波干扰强,且杂波与目的层反射波方向不一致的地震条件.本文先通过波场模拟,展示了TSBBRA方法具有形成定向地震波场的能力;而后通过对比相控震源与TSBBBRA时间剖面,说明了TSBBRA方法的有效性;最后在吉林某油页岩矿区,用TSBBRA方法,分别针对浅层目标与深层目标,生成定向地震波数据.与原始数据相比,目标层信噪比提高了3~35 dB,在时间剖面上观测到的深部目标信号从200 ms扩展到1000 ms,TSBBRA剖面资料与测区附近区域的地质与地震资料一致.由此得出结论,TSBBRA方法有助于改善目的层地震资料信噪比,当关注深部目的层时,由于TSBBRA方法能有效压制噪声,因此可用于能够实现更大的勘探深度.实验中,我们给出了浅层勘探结果,由于本方法对震源及观测系统没有限制,实际应用中TSBBRA方法可作为深部资源勘探领域提高深部地震资料信噪比的有效方法. 相似文献
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Characteristics of Seismic Wave Propagation in the Binchuan Region of Yunnan Using a Dense Seismic Array and Large Volume Airgun Shots 总被引：1，自引：1，他引：0
The Binchuan region of Yunnan is a structurally complex region with mountains, basins, and active faults. In this situation,seismic wave propagation exhibits complex characteristics due to strong heterogeneity of underground media instead of following the great-circle path. In order to obtain a high-resolution shallow crustal structure, a dense seismic array was deployed during March 21 to May 30, 2017 in this area. To better understand the complexities of seismic wave propagation in this region, we perform array-based frequency-domain beamforming analysis and single-station based polarization analysis to investigate the characteristics of seismic wave propagation, using airgun-generated P-wave signals recorded by dense array stations in this experiment. The results from these two methods both reveal similar but complex characteristics of seismic wave propagation in the Binchuan basin. The azimuth anomalies off the great-circle path are quite large with values up to 30°, which is caused by strong structural heterogeneity in the very shallow crust. Our research provide a better understanding of the complex geologic structures in this area and provide guidance for detecting concealed faults and distribution of velocity anomalies. 相似文献
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西准噶尔是我国大陆远离海岸带最远的地区.利用频率域聚束(或称f-κ分析)方法对布设在西准噶尔地区的两个不同尺度的三分量宽频地震台阵61天和31天的连续记录分别进行了低、高频背景噪声源分析.通过台阵响应函数的计算,确定了分析背景噪声源的最佳频带范围分别为0.04~0.1 Hz和0.5~3 Hz.对于低频背景噪声,分析了初次地脉动的震源,结果说明西准噶尔大尺度台阵(WJLA)在观测时间范围内可以接收到来自亚欧大陆周边几个海洋活动强烈的海岸带的背景噪声,尤其以来自北太平洋西海岸带和北大西洋东海岸带的信号最强.通过分析由两个强温带气旋引起的北大西洋的海浪剧烈运动产生的地脉动信号,证明了这两个强温带气旋与北大西洋东海岸带相互作用的区域有所不同,并发现了当这两个强温带气旋结束后,该海域依然会在较长的一段时间内保持活跃状态.对于高频背景噪声,在1~2.5 Hz频带范围内有一个持续而稳定的噪声源,来自于西准噶尔小尺度台阵(WJSA)中心北偏东60°方向,主要由克拉玛依市区及附近的人类活动产生;除此之外,在较低频段有时还会在270°~300°方位产生一个能量相对更强的噪声源,其信号传播速度更快,分析认为该类震源为测区西北部的多个矿山的采矿活动.本项实验研究证明:即使在远离海岸带的我国西北部地区,背景噪声仍具有足够强的信号,但噪声来源存在强烈的方向性,因此在该地区利用背景噪声对地球内部进行成像时,需要考虑噪声源方位特性对成像的影响. 相似文献
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V. Pinsky 《Physics of the Earth and Planetary Interiors》2006,158(1):75-83
The aim of this study is the design and trial of a novel sparse network beamforming (NB) technique to improve earthquake location. For this purpose bulletin phase arrival time data were processed via the use of complex exponents form and then used in an optimization via grid-search to search for the maximum semblance in hypocenter space. The use of the robust semblance statistic, provides reliable location results. The NB location results for a set of test events were compared to standard iterative ISC location procedure “iscloc” and its prototype the Jeffreys maximum likelihood estimator. For this purpose a data-base of 139 reference ground-truth events was extracted from the catalog of the International Seismological Centre (ISC) (97 GT5 events, assumed earthquakes, and 42 GT0 nuclear tests). The tuned NB procedure has shown excellent location results for events with a “good” ISC location and demonstrated the large epicenter deviations have been decreased in “bad” cases. Further developments of the algorithm would include allowances for 3D earth structure and a priori site-specific information. 相似文献
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