Analysis of broadband seismic noise at the German Regional Seismic Network and search for improved alternative station sites

The German Regional Seismic Network (GRSN) comprizes now 16 digital broadband stations equipped with Wieland-Streckeisen STS-2 seismometers, 24-bit dataloggers and a seismological data center at Erlangen. It covers the whole territory of Germany with station-spacings between 80 km to 240 km. The stations are sited in very different environments ranging from near shore at the Baltic Sea coast up to distances of about 700 km from the coast, both within cities and up to about 10 km away from any major settlement, industry or traffic roads. The underground varies from outcropping hard rocks in Hercynian mountain areas, sedimentary rocks in areas of Mesozoic platform cover to up to 1.5 km unconsolidated Quarternary and Tertiary subsoil. Accordingly, seismic background noise varies in a wide range between the upper and lower bounds of the new global noise model. The noise conditions at the GRSN have been investigated systematically by means of displacement power spectral analysis within the frequency range 10^-2 signal-to-noise ratio > 5 for RUE and > 10 for BSEG have been confirmed for frequencies between about 0.6 Hz 3 Hz. Strong lateral velocity and impedance contrasts between the outcropping Triassic/Permian sedimentary rocks and the surrounding unconsolidated Quarternary/Tertiary sediments are shown to be the main cause for the strong noise reduction and signal-to-noise ratio improvement at RUE and can account for about 50% of the noise reduction at BSEG.     

Noise Removal from Duplicate Paleoceanographic Time-Series: The Use of Adaptive Filtering Techniques

This study demonstrates that adaptive filters can be used successfully to remove noise from duplicate paleoceanographic time-series. Conventional methods for noise canceling such as fixed filters cannot be applied to paleoceanographic time-series if optimal filtering is to be achieved, because the signal-to-noise ratio is unknown and varies with time. In contrast, an adaptive filter automatically extracts information without any prior initialization of the filter parameters. Two basic adaptive filtering methods, the gradient-based stochastic least-mean-squares (LMS) algorithm and the recursive least-squares (RLS) algorithm have been modified for paleoceanographic applications. The RLS algorithm can be used for noise removal from duplicate records corrupted by stationary noise, for example, carbonate measurements, species counts, or density data. The RLS filter performance is characterized by high accuracy and fast rate of convergence. The modified LMS algorithm out-performs the RLS procedure in a nonstationary environment (e.g., stable isotope records) but at the price of a slower rate of convergence and a reduced accuracy in the final estimate. The application of both algorithms is demonstrated by means of carbonate and stable isotope data.     

高阻尼检波器在浅层地震勘探纵波反射法中的应用

在浅层地震勘探纵波反射法中,常规的动圈式检波器抗干扰能力有限,所接收的信号信噪比不高.高阻尼检波器能在信噪比等方面有很大提高,从而使我们的所采集的数据可信度更高更准.阐述了高阻尼检波器的各项性能指标及分析了其应用于浅层地震勘探纵波反射法中可行性和优越性,并介绍了一系列的实验和一个查找断裂构造带的工程实例,通过与其它类型检波器的对比分析,表明高阻尼检波器有较高的精度和信噪比,明显优于常规检波器.     

青藏高原东北缘背景噪声特征分析

采用2009年青藏高原东北缘55个数字化宽频带地震台站的垂直分量波形数据,计算了台站间噪声互相关函数,得到了Rayleigh经验格林函数。利用信噪比和归一化平均能量流的方法分析了青藏高原东北缘背景噪声源的方位分布和季节性变化特征。结果表明,5~10 s周期噪声源方位分布上较为稳定,不随季节变化,噪声源能量集中在105°~165°方向上,噪声源主要来自于太平洋。10~20 s周期噪声源季节性变化特征明显,夏季的噪声能量主要集中在165°~210°方向上,噪声源来自于印度洋海洋活动;冬季主要集中在300°~350°和165°~210°方向上,噪声能量主要来源于太平洋和北大西洋。     

改进Laplace的无人机图像边缘检测算法研究

当图像灰度发生急剧变化时,常规算法存在"阈值检测不敏感"的问题.针对这一问题,借鉴RGB三相分解变换的思路,基于Laplace算法基本原理,文中提出BRGB-ALaplace算法.该算法先进行图像增强,并用高斯滤波器平滑图像和抑制噪声;再对RGB 3个相位分量方向进行拉普拉斯模板锐化拉伸,对这3个分量进行相位重组,实现...     

Harmonic stochastic resonance-enhanced signal detecting in NW small-world neural network

The harmonic stochastic resonance-enhanced signal detecting in Newman-Watts small-world neural network is studied using the Hodgkin--Huxley dynamical equation with noise. If the connection probability p, coupling strength gsyn and noise intensity D matches well, higher order resonance will be found and an optimal signal-to-noise ratio will be obtained. Then, the reasons are given to explain the mechanism of this appearance.     

可控震源定向照明方法的仿真研究

当野外噪声很强,即使使用组合震源地震也无法获得满意信噪比的地震数据时,本文提出了一种基于可控震源阵列的定向照明控制方法,采用该方法可形成定向地震波.通过仿真研究合成了8激震器可控震源阵列分别采用简单组合及定向照明技术得到的单炮地震记录,可以看出采用合适的延时参数,定向照明单炮地震记录的反射波信噪比高于组合地震情况.定量的计算结果表明,实验条件下采用0.89 ms延时参数,各反射波信噪比分别提高了10.19 dB,3.23 dB和1.02 dB.由此可见,可控震源定向照明地震技术是一种提高原始地震资料信噪比的有效方法.     

信噪比检验法跟踪评估序贯平差质量研究

序贯平差有一套规律性很强的递推公式,易于编程实现且占用较小的内存,得到了广泛的实际应用。随着序贯进程的发展,观测信息不断丰富,使平差质量逐渐变好。本文对序贯平差质量跟踪检验问题进行了研究,提出了一种利用信噪比统计量,跟踪序贯平差过程评估中各待估参数估计质量的方法,并据此确定序贯平差进程的终止方式,在确保平差质量的同时有效地控制了计算的工作量。数值试验结果表明该方法合理有效,信噪比指标对序贯平差质量变化十分敏感。     

珠江口盆地东部YB油田海上多方位融合地震技术应用

针对珠江口盆地东部YB油田当前面临的高含水生产之压力,海上常规单方位拖缆地震资料难以满足对油田深层及周边滚动油气田开发目标的评价,故开展了海上多方位融合地震技术攻关。本次采取的主要技术方法是通过不同方位的三维二次地震采集,提高地下反射界面覆盖次数,增大地下反射点时距曲面能量面积。实践证明,海上多方位融合地震技术在研究区具有更好地压制采集脚印、提高信噪比、增加勘探目标照明度和改善地震资料成像品质等优势。研究结果表明, 海上多方位融合地震技术能够支持该油田现阶段稳产及推动周边的储量发现。     

海洋浅地层剖面资料的数据处理方法

在海上地球物理调查中,为了揭示浅部地层结构、浅层气、古河道以及其他潜在地质灾害,浅地层剖面测量是一种不可缺少的重要的手段之一,但是各种环境噪声的影响会导致采集到的原始资料质量不佳,影响后续的解释工作。以PARASOUND 70型参量式浅地层剖面仪实测资料为例,结合前人的研究成果,总结阐述了一些用于浅地层剖面资料的数据处理方法,提高了原始资料信噪比以及分辨率,为海洋地质结构的解释提供了良好的基础资料。