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1.
Three-component seismic and geoelectrical in-mine surveys were carried out in Lyukobanya colliery near Miskolc, Hungary to determine the in situ petrophysical parameter distributions and to detect inhomogeneities in the coal seam. The seismic measurements comprise an underground vertical seismic profile, using body waves, and an in-seam seismic amplitude-depth distribution and transmission survey, using channel waves. The geoelectrical measurements are based on the drift- and seam-sounding method. Interval traveltime-, amplitude-, multiple-filter- and polarization analysis methods are applied to the seismic data. They lead to a five-layer model for the strata including the coal seam. The coal seam and two underlying beds act as a seismic waveguide. The layer sequence supports the propagation of both normal and leaky mode channel waves of the Love- and Rayleigh type. A calculation of the total reflected energy for each interface using Knott's energy coefficients shows that the velocity ranges of high reflection energy and of normal and leaky mode wavegroups coincide. The excitation of wavegroups strongly depends on the seismic source. A simultaneous inversion of a geoelectrical drift- and seam-sounding survey prevents misinterpretations of the seismic data by clearly identifying the low-velocity coal seam as a high-resistivity bed. Calculations of dispersion and sounding curves improve the resolution of the slowness and resistivity in each layer. Both diminished amplitudes and distortions in the polarization of transmission seismo-grams and decreasing resistivities in a geoelectrical pseudosection of the coal seam are related to an inhomogeneity. A calculation of synthetic seismograms for Love and Rayleigh channel waves with the finite-difference and the Alekseev-Mikhailenko method agrees well with the field data for the main features, i.e., particular arrivals in the wave train, wavegroups, velocities and symmetries or asymmetries. This in-mine experiment demonstrates that the simultaneous acquisition, processing and interpretation of seismic and geoelectrical data improve the lithological interpretation of petrophysical parameter distributions. Coal seam inhomogeneities can also be detected more reliably by the two independent surveys than by one alone. 相似文献
2.
G. NEUMANN 《Geophysical Prospecting》1981,29(2):161-177
Lateral inhomogeneities generate fluctuations in the traveltime of seismic waves. By evaluation of these traveltime fluctuations from different source and receiver positions, lateral inhomogeneities can be located using a pseudo inverse matrix method (Aki, Christoffersson and Husebye 1977). The formulation of the problem is possible for transmitted waves as well as for reflected and refracted waves. In reflection seismics this method is of importance, if no reflections from the inhomogeneities themselves, but only reflections from lower boundaries can be observed. The basic assumptions for the mathematical formulation are (1) the average velocities and depths of the reflecting horizons are known already from standard processing methods, and (2) the traveltime residuals are due to lateral velocity changes between different reflectors or between reflectors and the surface. The area of the earth to be considered is divided into layers and the layers into rectangular blocks. The parallel displacement of a ray after passing a disturbed block is neglected, only the traveltime residual is taken into account. In this paper the method and its application to data obtained with two-dimensional models are described. 相似文献
3.
讨论非平稳、非线性局域波信号分解方法的物理意义和自适应性，数值实现三种局域波分解算法，研究局域波分解在地震信号时频分析中的应用方法和实践.通过Hilbert变换得到地震信号时频分布特征，与Fourier变换谱物理意义不同.采用一定的计算策略，改善瞬时频率计算精度，突出瞬时频率属性的物理意义；将局域波分解同Wigner分布结合，计算地震信号基于局域波分解的Wigner分布，抑制交叉项.模型和实际地震数据试算结果表明实现算法的正确性和有效性.研究表明：在地震信号时频分析中采用局域波分解求Hilbert谱具有自适应性，时域和频域的分辨率也较高；而基于局域波分解的地震信号Wigner分布，保留Wigner分布优良特性，抑制交叉项方法简单易实现；局域波分解方法适合处理地震信号，值得进一步研究和推广. 相似文献
4.
Part I of this series starts with a brief review of the fundamental principles underlying wave field extrapolation. Next, the total wave field is split into downgoing and upgoing waves, described by a set of coupled one-way wave equations. In cases of limited propagation angles and weak inhomogeneities these one-way wave equations can be decoupled, describing primary waves only. For large propagation angles (up to and including 90°) an alternative choice of sub-division into downgoing and upgoing waves is presented. It is shown that this approach is well suited for modeling as well as migration and inversion schemes for seismic data which include critical angle events. 相似文献
5.
宽方位高密度地震勘探可以有效的提高地震资料的空间分辨率和裂缝预测的精度,但地震道数的增加也大幅度提升了地震数据的处理成本.为提高海量地震数据偏移处理的计算效率,本文发展了一种快速射线束叠前时间偏移方法.该方法首先根据给定的射线束中心间隔将炮记录划分为一系列数据子集,然后利用倾斜叠加将数据子集分解为不同方向的平面波,最后根据射线束中心到地下成像点的双程走时和射线参数拾取相应的平面波振幅累加到成像点上.同Kirchhoff叠前时间偏移相比,本文方法不但保持了一致的成像精度,且由于仅需在稀疏的射线束中心位置进行成像累加运算,计算效率得到了大幅度的提升.文中所给出的模型和实际资料的测试结果验证了本文方法的正确性和有效性. 相似文献
6.
James G. Berryman 《Pure and Applied Geophysics》1988,128(1-2):423-432
Contrary to the traditional view, seismic attenuation in Biot's theory of fluid-saturated porous media is due to viscous damping of local (not global) pore-fluid motion. Since substantial inhomogeneities in fluid permeability of porous geological materials are to be expected, the regions of highest local permeability contribute most to the wave energy dissipation while those of lowest permeability dominate the fluid flow rate if they are uniformly distributed. This dichotomy can explain some of the observed discrepancies between computed and measured attenuation of compressional and shear waves in porous earth. One unfortunate consequence of this result is the fact that measured seismic wave attenuation in fluid-filled geological materials cannot be used directly as a diagnostic of the global fluid-flow permeability. 相似文献
7.
The interpretation of deep seismic sounding (DSS) data has been made on the basis of a two-dimensional inhomogeneous model. The refracted first arrivals as well as reflected and diffracted waves on the seismic records have been utilized. The seismic section was modeled in the iso-veolcity lines v(x, y) = const, taking into account the zones of diffraction associated with deep faults. Gravity observations have been used to construct a block model of the Earth's crust with vertical boundaries. It is suggested to define the base of the crust as the zone with velocities between 7.8 and 8.2 km/s. The reflecting boundaries of different length occurring in this zone can be conformal or unconformal with the iso-velocity lines near the base of the crust. As an example of our approach to the interpretation of DSS data the folded-blocky structure of the crust with horizontal inhomogeneities of velocity and density is shown in the Kzyl-Orda-Dzheskazgan profile in Central Kazakhstan. 相似文献
8.
The scattering of elastic energy by random clusters of fractures and/or cavities in a massive rock is studied. The interpretation of the scattered seismic response reveals crucial information about the clusters of inhomogeneities (fractures/cavities), which may correspond to reservoirs. The study is based on a new two‐dimensional numerical‐modelling method that relaxes the constraints on the location and orientation of the inhomogeneities, accounts for inhomogeneities that have almost no volume but a finite surface area (fractures) and improves the accuracy of the calculation when the size of the inhomogeneities is comparable to the mesh size. It is shown that the nature of the seismic response of zones of diffuse fracturing and/or cavities is associated with the non‐uniformity of micro‐inhomogeneities in such zones; accumulations of these micro‐inhomogeneities are known as clusters. The relationship between the non‐uniformity of micro‐inhomogeneities and the strength of the seismic response has been established and measured. Considerable differences in the structure of the seismic response of zones of diffuse fracturing and diffuse cavities have been identified. Converted PS‐waves dominate in the scattered wavefield associated with fractures. This is explained, as the modelling results show, by a greater transparency of fluid‐filled fractures, which reduces the reflected energy of compressional waves. The wavefield associated with cavities is characterized by the predominance (in terms of strength) of compressional PP‐waves. The strength of converted PS‐waves in the scattered wavefields for both media is approximately the same. On the whole, according to the results of the modelling, the energy of the scattered response of fractured reservoirs is considerably less (about two times) than that of cavernous reservoirs. 相似文献
9.
P. Gouédard L. Stehly F. Brenguier M. Campillo Y. Colin de Verdière E. Larose L. Margerin P. Roux F. J. Sánchez-Sesma N. M. Shapiro R. L. Weaver 《Geophysical Prospecting》2008,56(3):375-393
Random field cross‐correlation is a new promising technique for seismic exploration, as it bypasses shortcomings of usual active methods. Seismic noise can be considered as a reproducible, stationary in time, natural source. In the present paper we show why and how cross‐correlation of noise records can be used for geophysical imaging. We discuss the theoretical conditions required to observe the emergence of the Green's functions between two receivers from the cross‐correlation of noise records. We present examples of seismic imaging using reconstructed surface waves from regional to local scales. We also show an application using body waves extracted from records of a small‐scale network. We then introduce a new way to achieve surface wave seismic experiments using cross‐correlation of unsynchronized sources. At a laboratory scale, we demonstrate that body wave extraction may also be used to image buried scatterers. These works show the feasibility of passive imaging from noise cross‐correlation at different scales. 相似文献
10.
Born正演是一种常用的地震波场正演模拟方法,也是线性化地震反演的理论基础.在实际应用时,Born正演通常结合常规的地震射线方法进行实现.为了克服常规地震射线方法的弊端,并且保证地震波场的模拟精度和计算效率,本文提出了一种基于高斯束的一阶散射波场Born正演方法.该方法分为两个环节:首先,我们利用高斯束的走时和振幅信息将地下散射点处的反射率映射为地表束中心位置处的局部平面波;然后,我们利用逆倾斜叠加将局部平面波转化为接收点处的时空域散射波场.在具体的实施过程中,我们提出一种以wavelet-bank方式实现的局部平面波合成方法,同现有的算法相比,可以在保持计算精度的同时,大大减少计算时间;此外,我们还利用最速下降法优化了高斯束的迭代循环过程,进一步提高了Born正演的计算效率.两个模型的应用效果证明,本文所提出的高斯束Born正演方法可以精确、高效的实现声波介质一次散射波场的正演模拟,为三维大规模地震波场的正演问题提供了一种切实可行的实现方案. 相似文献
11.
一般而言,由于地下非均质体的存在所产生的二次波源,由它再生成新的波场,叫散射波场。目前,将散射波作为有效波来成像,已开始在溶洞和裂缝等特殊地质体的识别中得到应用。但对于野外资料采集来说,地表复杂地区,如戈壁、砾石区和山前带,大量存在的散射波却是干扰波,它们的存在会严重影响资料的品质,而其研究与实际应用国内外还很少。因此,通过正演模拟,分析散射波的基本特征,在此基础上研究散射波的去噪方法显得十分必要。本文从地震波运动学时距关系出发,研究了反射波和散射波的几何特征;然后用有限差分正演,模拟了散射波场,用理论模型研究并测试了局域双曲线Radon变换散射波去噪新方法。对于实际炮集资料,分析了F-K滤波方法压制散射噪声的局限,采用局域双曲Radon变换有效地去除了炮集中存在的散射噪声,取得了较好的应用效果。 相似文献
12.
三维复杂山地条件下的各种地震波型的走时计算技术,可以直接用于复杂山地区域地震波运动学特性的分析、地震数据采集观测系统的设计以及直接基于三维复杂地表的地震数据处理技术的研发.为了在三维复杂地表条件下准确、灵活且稳定地计算各种地震波型的走时,提出一种多级次群推进迎风混合法.该算法利用不等距迎风差分法简洁稳定地处理三维复杂地表及附近的局部走时计算问题,利用计算精度不错的迎风双线性插值法处理绝大部分均匀正方体网格中的局部走时计算问题,利用群推进法模拟三维复杂地表条件下地震波前的扩展问题,利用多级次算法处理各种类型的地震波的走时计算问题.算法分析和计算实例表明:新方法具有很好的计算精度与效率,且能灵活稳定地处理三维复杂地表复杂介质条件下的多波型走时计算问题. 相似文献
13.
场地放大效应的估计 总被引：2，自引：0，他引：2
本利用唐山地区9个台站得到的13次近场地震记录分析了场地放大效应，其中一些站位于废弃的地下煤矿坑道内，最深的一个台站在地下822m处，首先检验确定了地面反射波对地下场地的入射波没有很大影响，在后利用地下基岩场地台站（－822m)作参考场地，用线性反演法来同时分离震源，传播途径和局部场地效应，结果发现：在1至10Hz的频段上S波品质因子Qs基本上与频率成正比；与以地面基岩场地作参考场地所得的结果相比较，地面基岩场地的反应并不是一常数，它在大于6Hz的高频段上有明显的放大作用，在本的研究事件中，在6至10Hz的频段上这个放大纱数约为2至4。这表明由于地面基岩场地本身的放大作用，将导致在作场地震动预测时会低估地震作用，最后采用一种新的非参考场地法，即遗传算法，用w^2震源模型来估计绝对场地效应。在本的研究结果中，对大多数台站场地来说，所得的绝对场地应应与以地下基岩台站作参考场地所得的相对场地效应十分一致。这表明这作场地震动分析时，当仔细考虑了反射波对入射波的影响后，地下或井下基岩场地是比地面基岩场地更合适的参考场地。 相似文献
14.
The propagation of seismic waves through Earth models with slightly random lateral and vertical inhomogeneities superimposed on one composed of layers with vertical velocity gradients was investigated. The maximum deviation of velocity from a mean value at a given depth and a correlation distance derived from a two-dimensional smoothing filter were two parameters used to vary the amplitude and size of the velocity anomalies. The resulting models show short discontinuous reflectors scattered about at various depths throughout the model, and are thus in agreement with many deep seismic reflection experiments. On the other hand numerical experiments using ray-tracing techniques showed that the effect of the lateral and vertical velocity anomalies is to scatter the energy, and break up the continuous travel-time lines from vertical gradient models into travel-time segments with different slopes similar to those observed in many long range seismic refraction experiments, and to those resulting from layering effects in the media. Many of the numerical experiments which modelled the random crust produced a Pg segment and a P* segment with an apparent Conrad discontinuity at a depth of 10–20 km, this apparent depth being related to the correlation distance.When a seismic wave propagates through a heterogeneous Earth the amount of its energy which is converted into scattered energy will be a function of the inhomogeneous characteristics of the medium through which it has passed. If a ray passes through a homogeneous Earth the energy arriving at an array station should be relatively coherent whereas if the ray encounters lateral and vertical inhomogeneities its energy will be incoherent and much more complex. A series of coherency measurements done on array recordings of earthquakes at various distances showed that large lateral and vertical variations in complexity exist for different ray paths through the Earth with the region below the 650 km discontinuity in the mantle tending to be much simpler than the region just below the lithosphere. 相似文献
15.
As an ideal carrier of high-resolution information, seismic diffraction can be used to clarify and locate small-scale discontinuities or inhomogeneities in the subsurface. However, a diffraction is weak and thus be suppressed by the specular reflection. Furthermore, a diffraction would be destroyed by the conventional imaging method due to the polarity reversal of diffraction. In this paper, we analyse the behaviour of diffraction and reflection. For the image point on a horizontal or oblique reflector, the zone on both sides of the stationary point has the same energy after using a cosine weight function. Based on the behaviour, we propose the adaptive phase filter to adjust the polarity of the energy on both sides, and calculate it through the illumination angle and the reflector dip angle. This method avoids the calculation of the Fresnel zones and can further suppress residual reflection that disturb the diffraction images. Synthetic and field data applications show that the desired imaging results can be obtained by the proposed method. The test results demonstrate that the method is efficient in detecting small-scale discontinuities or inhomogeneities in the subsurface and can provide high-resolution information for seismic interpretation. 相似文献
16.
Ground roll is an interference wave that severely degrades the signal-to-noise ratio of seismic data and affects its subsequent processing and interpretation. In this study, according to differences in morphological characteristics between ground roll and reflected waves, we use morphological component analysis based on two-dimensional dictionaries to separate ground roll and reflected waves. Because ground roll is characterized by low-frequency, low-velocity, and dispersion, we select two-dimensional undecimated discrete wavelet transform as a sparse representation dictionary of ground roll. Because of a strong local correlation of the reflected wave, we select two-dimensional local discrete cosine transform as the sparse representation dictionary of reflected waves. A sparse representation model of seismic data is constructed based on a two-dimensional joint dictionary then a block coordinate relaxation algorithm is used to solve the model and decompose seismic record into reflected wave part and ground roll part.The good effects for the synthetic seismic data and application of real seismic data indicate that when using the model, strong-energy ground roll is considerably suppressed and the waveform of the reflected wave is effectively protected. 相似文献
17.
根据地震波场的线性叠加原理,提出了对地震共炮道集及其震源进行线性叠加的一般方案——广义地震数据合成的方法.利用这个方法,可以根据不同的地质情况和要求得到各种不同的人工合成地震数据道集和震源,如平面波数据道集和震源、局部平面波（束）数据道集和震源以及面向目标的人工合成地震数据道集和震源.对于人工合成地震数据道集的偏移成像可应用单平方根方程实现.不同的合成地震数据道集具有不同偏移成像特性：平面波数据道集具有很高的计算效率,局部平面波数据道集具有很好的方向性,面向目标的合成地震数据道集具有很好的面向目标特性. 相似文献
18.
19.
利用绿色、环保的人工震源,主动向地下发射地震波,构建地震雷达,实现大范围的地下探测,是地球科学的一个前沿课题.最早,探测地球内部利用的是天然地震产生的地震波,这是因为天然地震释放的能量大,一次天然地震释放的能量相当于万吨级炸药.几千公里远处仍可以接收到信噪比大于1的地震波信号,但天然地震发生频度低和震源位置定位精度低限制了利用天然地震进行地下探测的精度;后来,利用人工源的地震勘探得到迅速的发展,探测精度明显提高,但受到人工源能量的限制,探测的空间尺度有限;今天,以小当量激发实现大尺度探测是发展地震雷达的一个关键问题,是将地震波理论和现代信息科学相结合的一个新的领域.发展人工震源的编码和接收信号的解码等理论和技术,可以从电磁波雷达在过去半个世纪所经过的道路得到许多借鉴和启发.可以预期,地震雷达的发展将会对观测地震学带来全面的影响. 相似文献
20.
描述地震波衰减特征的品质因子Q对地震数据处理和油藏描述非常重要,在地震勘探领域,Q值一般通过垂直地震剖面(VSP)数据或地面地震数据得到.由于叠前地面地震数据具有复杂的射线路径且存在噪声、调谐干涉效应等影响,从叠前地震数据中准确估计Q值相对困难.本文以地震波射线传播为基础,根据同相轴局部斜率和射线参数的映射关系,将多射线波形频谱同时带入谱比法联合反演估计Q值,提出了基于多射线联合反演的速度无关叠前Q值估计方法.该方法通过局部斜率属性避开了速度对Q值估计的影响,局部斜率携带地震波传播的速度信息,具有相同局部斜率的地震反射波具有相同的传播射线参数.同相轴局部斜率是地震数据域的属性,而速度是模型域的参数,在估计Q值中采用数据域的属性参数可以直接应用于数据的联合反演,而不需要通过速度对其做进一步的转化,从而提高了Q值估计的精度.同时,本方法采用预测映射(predictive mapping)技术将非零炮检距反射信息映射到零炮检距处,从而获得零偏移距走时对应的Q值.模拟和实际算例验证了本文方法的有效性. 相似文献