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在地震勘探中,近地表的不均匀性给激发、接收和静校正等带来很大的困难.WX地区浅表层分布有多期火成岩,对地震勘探造成很大的影响,本文实际工作从发分析了各种地震表层结构调查方法,并对小折射、井中激发地表接收微测井和地表激发井中接收的微测井等常用方法,进行了同点对比试验.选择了最合适的表层结构调查方法,辅以钻井岩性描述,建立了工区的详细准确的表层岩性变化模型,指导地震野外采集方法设计,并求取模型静校正量.取得了较好的地震资料. 相似文献
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为了研究二氧化碳物理相变技术应用于新型震源研发的可行性,在地下成层性较好的某煤田地震测区,开展了利用二氧化碳相变技术激发地震波的野外人工震源激发-接收实验．并与传统炸药震源进行了对比．地震数据利用Aries2.66型垂直分量反射地震仪和PDS-2型三分量地震仪接收．根据实测地震数据,从野外地震记录震相识别,初至波传播距离分析,震源近场地震信号时频分析,CO_2相变激发震源子波提取和基于CO_2震源子波的地震初至波波形反演实验等多个方面,进行了关于CO_2相变激发技术能否产生地震波信号以及能否将其应用于新型震源研发的可行性研究．研究结果表明CO_2物理相变膨胀能够产生能量集中的地震波信号;在实验区地质条件和激发参量下地震记录中初至波的可识别的传播距离约为1km;震源近场地震信号的主频集中在8～13Hz;利用震源近场数据提取了CO_2震源子波;通过地震初至波波形反演实验认为这种震源子波能够应用于波形反演等方面的研究．因为CO_2相变激发具有绿色、环保、安全等方面的优点,若能进一步在激发能量、激发—延迟时间一致性等方面加以改进,该技术有望在城市隐伏活动断层探测、城市地下空间探测、煤矿高瓦斯环境人工地震勘探等领域发挥重要的作用． 相似文献
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Using an airgun array in a land reservoir as the seismic source for seismotectonic studies in northern China: experiments and preliminary results 总被引：15，自引：0，他引：15
This paper reports the field setup and preliminary results of experiments utilizing an airgun array in a reservoir in north China for a seismotectonic study. Commonly used in offshore petroleum resource exploration, the airgun source was found to be more useful than a traditional explosive source for large‐scale and long offset land seismic surveys. The airgun array, formed by four 1,500 in3 airguns (a total of 6,000 in3 in volume) was placed at a depth of 6–9 m into the reservoir to generate the pressure impulse. No direct evidence was found that the airgun source adversely affected the fish in the reservoir. The peak ground acceleration recorded on the top of the reservoir dam 100 m away was 17.8 gal in the horizontal direction; this is much less than the designed earthquake‐resistance threshold of 125 gal for this dam. The energy for one shot of this airgun array is about 6.68 MJ, equivalent to firing a 1.7 kg explosive. The seismic waves generated by the airgun source were recorded by receivers of the regional seismic networks and a temporary wide‐angle reflection and refraction profile formed by 100 short‐period seismometers with the maximum source‐receiver offset of 206 km. The seismic wave signature at these long‐offset stations is equivalent to that generated by a traditional blast source in a borehole with a 1,000–2,000 kg explosive. Preliminary results showed clear seismic phases from refractions from the multi‐layer crustal structures in the north China region. Forward modelling using numerical simulation confirms that the seismic arrivals are indeed from lower crustal interfaces. The airgun source is efficient, economical, environmentally friendly and suitable for being used in urbanized areas. It has many advantages over an explosive source for seismotectonic studies such as the high repeatability that is supreme for stacking to improve signal qualities. The disadvantage is that the source is limited to existing lakes or reservoirs, which may restrict experimental geometry. 相似文献
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Kamal Abdel-Rahman El-Sayed 《地震研究》2008,31(2):160-170
根据埃及Gasco天然气公司工程场地的现场调查资料、地震活动性和地震灾害评估结果,对该场地进行了评估.通过浅源地震波折射勘探,对8个地震剖面上的土壤和岩石的弹性动态常数进行了分析.场地地面模型包括两层,分析表明它们具有从中值到高值的弹性动态常数,说明场地有良好的土壤条件和基岩岩性.同时,我们搜集和分析了研究区周围150 km半径范围内的历史和仪器记录地震,从构造环境、地震活动性、地质构造和主要地震的断层面解等方面进行了研究,认为场地受4个震源区的影响:苏伊士中部海湾、开罗-苏伊士地区、开罗西南和Beni-Suef地区.我们采用地震活动性统计方法并结合专家判定,确定了这些震源区内最大地震的矩震级(MW).另外,依据场地峰值加速度(PGA)和反应谱,用随机方法对场地进行了地震灾害评估.4个震源区中,Beni-Suef地区距离工程场地最近,其PGA最大值为9.34cm/s2,但这个值很小,表明地震不会对工程场地产生破坏性影响.最后,我们还模拟了阻尼为1%、3%和5%时的伪加速度场地反应谱. 相似文献
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为研究震源和水听器电缆沉放深度对单道地震勘探的影响,建立鬼波影响模型,采用雷克子波模拟震源子波,分析因震源及水听器电缆沉放深度产生的鬼波对一次有效反射地震波的影响,并采用不同震源和水听器电缆沉放深度的数据对本次研究结论进行验证。研究表明：地震剖面分辨率和震源及水听器电缆沉放的总深度呈反比;随着震源或水听器电缆沉放深度的增加,地震剖面的分辨率递减,接收地震波能量从低值递增到最大值,再从最大值缓慢降低到稳定值;当水听器电缆沉放深度小于168.8/f(m)时,接收地震波能量随震源沉放深度变化的波动相对平缓,水听器电缆沉放深度浅有利于地震波的一致性,但沉放深度过浅时接收地震波能量将被极大削弱,会明显降低地震波的有效穿透深度;当震源沉放深度约为292.3/f(m)时,一次有效反射波的峰值和震源鬼波的峰值重叠,接收地震波能量最大;当震源沉放深度大于584.6/f(m)时,不考虑地震波能量在水中衰减的情况下,震源沉放深度继续增加对接收地震波能量的增加无效。 相似文献
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国内外大量地震震例研究表明，巨大的城市地震灾害主要是由隐伏于城市之下的活动断裂上发生的地震造成的，因此，探测城市活断层是十分必要和紧迫的。高分辩率地震勘探是目前探测城市活断层较为有效的地球物理方法，它包括激发技术、接收技术、观测系统、地震数据处理与解释技术等。而震源是地震勘探的首要问题，城市特定的人文环境和城市活断层的特点对高分辩率地震勘探的震源提出了特殊的要求，较小的断距决定了要有较宽的震源谱，城市较严重的干扰决定了震源勘探的震源提出了特殊的要求，较小数点的断距决定了要有较宽的震源谱，城市较严重的干扰决定了震源要有较强的抗干扰能力。通过在福州市跨八一水库断裂进行的可控震源、真空加速落锤、锤击震源、枪震源以及炸药震源的试验研究，利用频谱分析技术，得到了各种震源谱的特征，并给出了可控震源、真空加速落锤和锤击震源叠加时间剖面对比，探讨了各种震源在城市活断层探测中的有效性。 相似文献
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无线数字遥测地震台网的信道测试 总被引：1，自引：0，他引：1
在无线数字遥测地震台网中,信道测试是台网传输的关键环节,关系到台网的运行率和地震信号的可用率,甚至整个台网建设的成败。信道测试有3方面的内容:中继站背景场强测试、子台信道储备测试和信道误码测试。经测试后得到各种参数柱状图,以此判断每个台站的信道质量情况,及时调整台网信道传输的设计方案,确保成功建成无线数字遥测地震台网。 相似文献
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The basic aspects of testing small-scale masonry building models on simple earthquake simulators are discussed. Since the scale effects represent a difficult problem to solve, the overall seismic behaviour of structural systems, and not the behaviour of structulal details, has been studied by testing the reduced-sized models on a simple earthquake simulator. Accurate results regarding the dynamic behaviour and failure mechanism of the tested structures have been obtained by means of testing the relatively simple, adequately designed small-scale masonry building models. A simple earthquake simulator capable of simulating the uni-directional earthquake ground motion has been developed to study the seismic behaviour of masonry building models. Although a multipurpose programmable actuator was used to drive the shaking table, the comparison of the dynamic characteristics of the generated shaking-table motion and the earthquake acceleration records used for the simulation of seismic loads showed an acceptable degree of correlation between the input and output seismic motion. 相似文献
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Passive seismic has recently attracted a great deal of attention because non‐artificial source is used in subsurface imaging. The utilization of passive source is low cost compared with artificial‐source exploration. In general, constructing virtual shot gathers by using cross‐correlation is a preliminary step in passive seismic data processing, which provides the basis for applying conventional seismic processing methods. However, the subsurface structure is not uniformly illuminated by passive sources, which leads to that the ray path of passive seismic does not fit the hyperbolic hypothesis. Thereby, travel time is incorrect in the virtual shot gathers. Besides, the cross‐correlation results are contaminated by incoherent noise since the passive sources are always natural. Such noise is kinematically similar to seismic events and challenging to be attenuated, which will inevitably reduce the accuracy in the subsequent process. Although primary estimation for transient‐source seismic data has already been proposed, it is not feasible to noise‐source seismic data due to the incoherent noise. To overcome the above problems, we proposed to combine focal transform and local similarity into a highly integrated operator and then added it into the closed‐loop surface‐related multiple elimination based on the 3D L1‐norm sparse inversion framework. Results proved that the method was capable of reliably estimating noise‐free primaries and correcting travel time at far offsets for a foresaid virtual shot gathers in a simultaneous closed‐loop inversion manner. 相似文献
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Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m underground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes, shorten survey period, and reduce engineering cost to some extent. 相似文献
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地球深部结构研究是地震预报和地球动力学研究的基础,传统人工地震受到探测深度、分辨率或震源能量的环保限制,探索利用小能量震源进行深部高分辨率探测技术具有重要意义.本文借鉴雷达探测中的编码原理,开展了震源编码探测实验,利用人工震源向地下发送具有独特特征的随机编码序列脉冲,作为一次等效激发,利用准确记录的编码震源的源函数与地震连续观测的互相关进行“解码”分析,获取地下信息,形成编码地震探测技术.实验表明编码地震能够大幅度提高地震探测能力,利用小能量震源获得远距离的探测和高分辨率,是一种具有重要发展前景的人工探测技术. 相似文献
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Tatiana Pertuz Alireza Malehmir Jordan Bos Bojan Brodic Yinshuai Ding Richard de Kunder Paul Marsden 《Geophysical Prospecting》2022,70(1):79-94
A prototype electromagnetic vibrator, referred to here as E-Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E-Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two-dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E-Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E-Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E-Vib source for improved targeting in hardrock geological settings. 相似文献
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Progress in the imaging of the mantle and core is partially limited by the sparse distribution of natural sources; the earthquake hypocenters are mainly along the active lithospheric plate boundaries. This problem can be approached with seismic interferometry. In recent years, there has been considerable progress in the development of seismic interferometric techniques. The term seismic interferometry refers to the principle of generating new seismic responses by cross‐correlating seismic observations at different receiver locations. The application of interferometric techniques on a global scale could create sources at locations where no earthquakes occur. In this way, yet unknown responses would become available for the application of travel‐time tomography and surface‐wave dispersion studies. The retrieval of a dense‐enough sampling of source gathers would largely benefit the application of reflection imaging. We derive new elastodynamic representation integrals for global‐scale seismic interferometry. The relations are different from other seismic interferometry relations for transient sources, in the sense that they are suited for a rotating closed system like the Earth. We use a correlation of an observed response with a response to which free‐surface multiple elimination has been applied to account for the closed system. Despite the fact that the rotation of the Earth breaks source‐receiver reciprocity, the seismic interferometry relations are shown to be valid. The Coriolis force is included without the need to evaluate an extra term. We synthesize global‐scale earthquake responses and use them to illustrate the acoustic versions of the new interferometric relations. When the sampling of real source locations is dense enough, then both the responses with and without free‐surface multiples are retrieved. When we do not take into account the responses from the sources in the direct neighborhood of the seismic interferometry‐constructed source location, the response with free‐surface multiples can still be retrieved. Even when only responses from sources at a certain range of epicentral distances are available, some events in the Green's function between two receiver locations can still be retrieved. The retrieved responses are not perfect, but the artefacts can largely be ascribed to numerical errors. The reconstruction of internal events – the response as if there was a source and a receiver on (major) contrasts within the model – could possibly be of use for imaging. With modelling it is possible to discover in which region of the correlation panel stationary phases occur that contribute to the retrieval of events. This knowledge opens up a new way of filtering out undesired events and of discovering whether specific events could be retrieved with a given source‐receiver configuration. 相似文献
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Trans‐dimensional Bayesian inversion of controlled‐source electromagnetic data in the German North Sea 
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下载免费PDF全文 Romina A. S. Gehrmann Jan Dettmer Katrin Schwalenberg Martin Engels Stan E. Dosso Asli Özmaral 《Geophysical Prospecting》2015,63(6):1314-1333
This paper presents the first controlled‐source electromagnetic survey carried out in the German North Sea with a recently developed seafloor‐towed electrical dipole–dipole system, i.e., HYDRA II. Controlled‐source electromagnetic data are measured, processed, and inverted in the time domain to estimate an electrical resistivity model of the sub‐seafloor. The controlled‐source electromagnetic survey targeted a shallow, phase‐reversed, seismic reflector, which potentially indicates free gas. To compare the resistivity model to reflection seismic data and draw a combined interpretation, we apply a trans‐dimensional Bayesian inversion that estimates model parameters and uncertainties, and samples probabilistically over the number of layers of the resistivity model. The controlled‐source electromagnetic data errors show time‐varying correlations, and we therefore apply a non‐Toeplitz data covariance matrix in the inversion that is estimated from residual analysis. The geological interpretation drawn from controlled‐source electromagnetic inversion results and borehole and reflection seismic data yield resistivities of ～1 Ωm at the seafloor, which are typical for fine‐grained marine deposits, whereas resistivities below ～20 mbsf increase to 2–4 Ωm and can be related to a transition from fine‐grained (Holocene age) to unsorted, coarse‐grained, and compacted glacial sediments (Pleistocene age). Interface depths from controlled‐source electromagnetic inversion generally match the seismic reflector related to the contrast between the different depositional environments. Resistivities decrease again at greater depths to ～1 Ωm with a minimum resistivity at ～300 mbsf where a seismic reflector (that marks a major flooding surface of late Miocene age) correlates with an increased gamma‐ray count, indicating an increased amount of fine‐grained sediments. We suggest that the grain size may have a major impact on the electrical resistivity of the sediment with lower resistivities for fine‐grained sediments. Concerning the phase‐reversed seismic reflector that was targeted by the survey, controlled‐source electromagnetic inversion results yield no indication for free gas below it as resistivities are generally elevated above the reflector. We suggest that the elevated resistivities are caused by an overall decrease in porosity in the glacial sediments and that the seismic reflector could be caused by an impedance contrast at a thin low‐velocity layer. Controlled‐source electromagnetic interface depths near the reflector are quite uncertain and variable. We conclude that the seismic interface cannot be resolved with the controlled‐source electromagnetic data, but the thickness of the corresponding resistive layer follows the trend of the reflector that is inclined towards the west. 相似文献
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Potential sources are aggregates of probable future epicenters.In this area,for source models currently,in common use for seismic risk analysis in China,the mean area of each potential source is about 3000-4000 km2.It is assumed that seismic risk has a uniform distribution within the range of each potential source,but studies have shown that the uniform distribution model to a large extent may give an underestimation of the seismic risk.In this paper,the relative distribution of historical epicenters in space within potential sources is discussed,a method is proposed to quantitatively describe the non-uniform distribution of strong earthquakes within potential sources,and some preliminary results are given.By using the results of this paper,seismic risk analysis and seismic zonation can be made more scientific and more reasonable. 相似文献
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A high-fidelity PC-based control system has been developed to improve the tracking characteristics of a small-scale seismic motion simulator used for testing structural control designs. This work outlines the development and testing of the control system. First, the simulator hardware is described in detail. The process of constructing a mechanistic model of the system and identifying model parameters is then described. Next, a closed-loop feedback/feed-forward control algorithm, based on an optimal receding horizon formulation, is developed. The control design was tested and the results indicate that the seismic shake table precisely tracked reference seismic motions. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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组合震源技术通过调节延迟激发时间和震源埋藏深度能够实现地震波场的定向传播,提高地震波的照明能量和地震数据信噪比.然而,目前国内外对基于特定目标的组合震源最佳聚焦方向的选取以及起伏地表组合震源定向理论的研究相对较少.在聚焦方向选取方面,目前基本是利用多种不同延时参数的组合震源分别进行试验,从而确定较好的组合震源延时参数.本文则利用爆炸反射面原理,在目的层界面上均匀布置震源同时激发地震波,能够产生垂直于地层界面传播的平面波,当初至波传播至地表时进行地表方向统计.根据互易性原理,以初至波传播方向的反方向为聚焦方向,激发产生的地震波主波束方向将垂直入射到目的层界面上,从而精确的计算出组合震源的最佳聚焦方向.在组合震源定向方面,目前主要是利用组合震源方向因子公式进行计算,但该方法要求震源布置在同一条直线上,并不能满足起伏地表的应用要求.本文以惠更斯-菲涅尔原理为理论基础,提出通过炮点向量在聚焦方向上的投影来确定组合震源传播至虚拟波前的走时,从而确定任意起伏地表组合震源的延迟激发时间.该方法不仅能够计算出沿给定地质模型的目的层界面垂直入射的组合震源聚焦方向,也能够确定任意起伏地表情况下形成沿该聚焦方向定向传播地震波场的组合震源延迟激发时间.因此,本文提出的面向目标的起伏地表组合震源延时参数计算方法对组合震源数据采集具有理论与实践意义. 相似文献
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本文提出解调包络方法来重构地震记录中缺失的低频信号,同时该方法能够降低全波形反演的非线性程度;提出伴随状态震源函数反演方法来得到精确的震源函数,并推导了梯度计算公式;解调包络方法结合低通滤波技术,实现了从低频到高频的多尺度反演策略,有效缓解了全波形反演的周波跳跃问题.数值算例证明了解调包络、伴随状态震源函数反演方法和低通滤波多尺度反演策略的可行性及优越性.震源函数反演精度测试结果表明:即使观测记录在缺失低频信息的情况下,也能反演得到精确的震源函数.缺失低频测试和抗噪能力测试结果表明:即使地震数据中缺失9Hz以下的低频信号或者信噪比极低的情况下,利用反演得到的精确震源函数进行解调包络多尺度全波形反演,同样可以得到高精度的全波形反演结果.与Hilbert包络全波形反演对比结果表明:解调包络在重构低频和降低伴随震源主频方面具有一定优势. 相似文献