共查询到20条相似文献，搜索用时 93 毫秒
1.
复杂构造和非均匀介质对时距曲线同相轴的弯曲形成了非双曲线型曲线。如按双曲线正常时差动校正方法计算动校正量,必然使反射波叠加效果不理想。本文使用非双曲线高保真动校正方法计算剩余动校正量△△T,然后对反射信号实行整体移动,避免波形拉伸畸变,提高地震剖面的保真度、信噪比和分辨率。用FORTRAN语言,在TIPEX系统中开发了计算程序,该程序调用方便,对实际资料处理后的反射波道集同相性和叠加剖面质量都较常规正常时差动校正处理效果好。 相似文献
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基于反射波的静校正技术,通常是在反射波CMP叠加剖面上,选择波组连续性好,信噪比高的反射层作为参考层制作模型道,然后再利用互相关的方法求取炮点和接收点的静校正量。当反射波的信噪比过低时,常规的剩余静校正方法由于不能建立准确的模型道而失效。折射静校正采用信噪比较高的初至波进行静校正计算,效果稳定。初至是否平滑,往往作为静校正效果的一个判断准则。这里基于短波长静校正量的随机性和初至与反射波时差变化的一致性二个假定条件,提出了拟合初至利用误差分配的方法,进行静校正量的求取。通过对实际资料静校正处理前、后对比,验证了该算法的正确性和适应性。 相似文献
3.
多次波压制是海洋地震数据处理的关键,如何保护一次反射波的同时高效准确地识别并压制多次波是地震资料处理的重点。笔者在共中心点(CMP)叠加压制多次波方法的基础上,基于CMP道集地震信号与叠加道地震信号的相似性特征在S变换域进行多次波压制。首先,利用多次波速度动校正并对CMP道集数据减去叠加道数据完成第一次多次波减除,此时,波场中残余的多次波以随机噪声的形式存在;然后,对减除多次波的地震波场应用一次波速度动校正,并以一次波速度叠加道为初始模型对CMP道集S变换谱进行相似性滤波完成第二次残余多次波去除。针对理论数据和实际数据进行了有效性测试,结果表明本文所提方法能够较好地压制多次波,提高反射波的成像精度。 相似文献
4.
《物探化探计算技术》2017,(3)
随着3D地震勘探技术的发展,对各向异性介质地震波传播理论的研究也在不断深入。不考虑HTI介质影响的动校正后的叠前CMP道集中仍存在着"正弦型"的剩余时差,传统的基于Dix时差公式的速度分析和动校正已无法满足处理的精度要求。通过借鉴统计剩余静校正的参考道互相关法和最小方差法,并结合HTI介质特征,提出了基于参考道的统计各向异性时差校正方法。提取各向异性时差并进行校正,对其叠加道的纵向分辨率的提高进行了定量分析。实验结果表明,统计各向异性剩余时差校正法消除了由HTI介质产生的剩余时差,同时也提高了纵向分辨率,从而使叠加剖面的质量得到显著提高。 相似文献
5.
在叠前共深度点道集内各地震道的动、静校正误差很小的情况下,地震资料时间域水平叠加方法有较好的叠加结果.但是,如果动、静校正的误差较大时,叠加效果将受到影响,即叠后振幅和分辨率都会降低.因此,提出一种频率域叠加方法.该方法既具有常规水平叠加方法能提高信噪比的优点,又能将共深度点道集内的走时时差消除,达到同相叠加的目的.几个比较叠加方法效果的有噪CDP道集叠加的例子证明了该方法的效果. 相似文献
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纵波VTI介质各向异性参数的求取 总被引：2，自引：0，他引：2
在新疆塔里木盆地某地区的宽方位三维地震数据中,通过速度分析和不同炮检距范围数据的叠加剖面的比较,发现了各向同性基于双曲线时差曲线的NMO动校正时,远炮检距数据存在比较大的剩余动校正量。分析表明,是由于VTI介质火成岩的各向异性和垂向速度变化引起非双曲线时差。应用纵波短排列地震数据求取的均方根动校正速度,分别以扫描法和旅行时法得到了各自相互验证的各向异性参数。最后,利用所提取的各向异性参数,进行VTI介质各向异性速度分析、动校正和成像,剩余动校正得到消除,成像质量得到明显改善。 相似文献
9.
折射静校正技术在宣东地震资料处理中的应用 总被引：1，自引：0，他引：1
当地震数据中存在较大的静校正量时，利用模型道与各道互相关求取时差的反射波静校正方法往往不能奏效，其主要原因是得不到好的模型道，当原始资料的信噪比很低时，这一问题更加突出，因此必须首先解决好野外一次静校正。近年来，针对复杂地形和地表结构的折射波静校正，总差分折射静校正方法和基于速度模型的反演静校正方法被广泛应用。在静校正问题严重的宣东地区为例，综合运用了这两种折射静校正方法进行三维地震资料的处理，取得良好效果。 相似文献
10.
在我国西部地区由于表层激发接收条件差, 常采用高叠加次数的地震观测技术。在地震数据处理中, 在进行了地形校正和基准面校正之后, 还存在数十毫秒的剩余静态时差。在叠加剖面上, 这种静态时差对反射波的起伏形态的影响具有浅中深层的差异性, 即出现了"静校不静"的现象。分析表明 , 这种现象是由叠加次数高、排列偏移距大, 在同一个CMP道集中, 浅、中、深层参加叠加的道数差异较大, 导致叠加过程中对静态时差平滑作用的差异所致。与岩石裸露山区中因反射波传播路径差异形成的非地表一致性"静校不静"现象不同, 仍然是"地表一致性"的。分析产生这种现象的原因, 为正确进行静校正打下基础。 相似文献
11.
大炮检距优化6次NMO校正 总被引：1，自引：0，他引：1
常规2次NMO动校是假定炮检距与深度比值小，并且射线为直线。计算的旅行时精度随着炮检距与深度比值的增加而大大降低，NMO校正能通过高次(4次、6次)项逼近得到改善。因此，在大炮检距情况下，若直接忽略高次项，则计算旅行时会产生很大误差。所以在大炮检距条件下进行2次NMO近似不利于速度分析、AVO研究和CMP道集动校叠加。笔者引入了一个更精确的旅行时近似计算，称为优化6次NMO动校方程式，因为截断误差较小，故其精确度高于泰勒6次展开式。通过模型和实际数据的试验，证明大炮检距优化6次NMO方程精度高，更具有实际应用意义。 相似文献
12.
先后推导了水平层与倾斜层2-D横向各向同性介质地震波反射波走时曲线方程,并就似SH波进行了模型计算,发现2-D情况下,似SH波的反射波走时曲线基本上符合双曲线形式。 相似文献
13.
This paper is devoted to a geostatistical attempt at modeling migration errors when localizing a reflector in the ground. Starting with a probabilistic velocity model and choosing the simple geometrical optics background for the wave propagation in such media, we give the expression of the errors. This may be quantified provided the covariance of the velocity field is known. Variance of arrival times at constant offset is related to the covariance of the velocity field at hand. A practical application is given in the same paragraph. After that we give a typical schema for migration and uncertainty modeling: starting with seismic data, we make the weak seismic inversion. We then obtain the covariance of the velocity field that we use for simulating migration errors. The main issues of this methodology are discussed in the last paragraph. 相似文献
14.
由于介质的非均匀性,反射层的弯曲性,以及介质的各向异性,使得反射波旅行时不再是双曲线的形式,从而使常规动校正产生较大误差。这里从理论上分析了大偏移距处出现动校不平的原因,指出了介质的各向异性是影响地震资料大偏移距处速度分析精度的主要因素,并对Hake、Castle和Alkhalifah三种各向异性动校正理论及其应用效果做了细致研究。结果表明,在偏移距～深度比小于"1"时,几种动校正方法与常规动校正差别不大:在大偏移距处,Hake方法具有较大的误差;Castle能够得到较好的效果;Alkhalifah方法在大炮检距任意各向异性强度下都可以得到比较精确的校正结果。对应用效果最好的Alkhalifah各向异性动校正进行了算法实现,并基于Java语言的开发环境,编制了各向异性速度分析和非双曲动校正的软件,在模型测试和实际资料的应用中取得了良好的效果。 相似文献
15.
基于波前重建和李代数积分的地震波走时计算 总被引：1，自引：0，他引：1
地震波走时计算在数值模拟、层析反演和偏移成像中均有重要意义。将波前重建与李代数积分相结合,提出了一种新的适应横向变速介质的非对称走时算法,称之为wave-front construction-Lie algebra integral(WFC-LAI)算法。本算法利用一次波前重建计算成像射线走时进行坐标变换,将深度域单平方根算子透镜项转化为常数,在射线坐标系下计算李代数积分和指数映射,得到地震波走时的解析表达式。数值试验表明,该方法计算结果与线性横向变速介质中走时的理论值吻合。通过与波前重建结果对比,WFC-LAI算法对于求取横向变速介质中地震波走时是可行的,节省了存储空间,易于并行,有利于提高Kirchhoff积分叠前深度偏移的精度和效率。 相似文献
16.
We present the mathematical deduction and properties of the mean traveltime curves for homogeneous elliptical anisotropic
media. These curves generalize their isotropic counterparts which have been introduced in the past as a simple data quality
analysis technique at the pre-inversion stage for 2D transmission experiments, allowing the inference of prior velocity models
to gain stability at the tomographic inversion. Also, the anisotropy parameters (maximum velocity, anisotropic direction and
ratio) are shown to affect the shape of these curves. The degree of asymmetry of the anisotropic mean traveltime curves (displacement
of the mean time and standard deviation minima from the middle of the gathering line) is related to the direction of anisotropy
which can then be visually estimated. Least squares’ fitting of the anisotropic theoretical models to their experimental counterparts
is an effective method to estimate at the pre-inversion stage a macroscopic elliptical anisotropic velocity model, valid at
the scale of the experiment, and able to match the experimental mean traveltime distribution.
Sensitivity analysis has shown that the mean curve is less prone to errors than the standard deviation curve. Parameter identification
from the standard deviation curve becomes unstable for noise levels higher than 5%; data errors produce smearing of the value
of the estimated anisotropy ratio and wrong directions of anisotropy biased towards zero degrees. Also, identification from
the mean traveltime curve becomes stable when the maximum velocity is well constrained. Finally, this methodology is illustrated
with the application to the Grimsel data set. Performing MTC analysis is always recommended since it does not need high numerical
requirements, and as shown in the sensibility analysis section, errors in data can be misinterpreted as geological anisotropies.
J.L. Fernández Martínez is a visiting professor at UC Berkeley, Department of Civil and Environmental Eng., CA 94720-1710. 相似文献
17.
V. B. Piip 《Moscow University Geology Bulletin》2009,64(5):296-305
The paper discusses the mantle structure along superlong seismic profiles in Russia examined using the method of homogenous
functions. Two-dimensional heterogeneous sections of the upper mantle were calculated from travel-time curves to a depth of
500–600 km with allowance for the Earth’s curvature without using any a priory information. The presentation of sections as
surfaces with a shaded relief combined with velocity contours allowed discerning the principal interfaces in the lithosphere
and in the upper mantle, the internal structure of layers, and local heterogeneities of different shapes (convective cells
and slabs) in the sections. 相似文献
18.
The analysis of measured stress waves for the prediction of static pile capacity is described. The usual method of using the measured velocity record as the input boundary condition in a wave equation analysis with a finite element model, if not properly implemented, can lead to significant numerical errors. An alternative scheme using an accurate prescribed displacement procedure with the measured displacement record (obtained from the integration of the velocity) is proposed, and is shown to be very efficient. These aspects of the numerical modelling procedure are illustrated by a case study. 相似文献
19.
This paper describes an experimentally based procedure for building dynamic P–Y curves for clays from the Campeche sound in the Gulf of Mexico and for Mexico City clays. Cyclic triaxial and resonant column tests were used to derive hyperbolic stiffness–strain and damping–strain functions that depend on soil plasticity and on relative consistency. The dynamic P–Y curves incorporate these functions and also include hysteretical and geometrical damping characteristics of the pile–soil system; they can be used directly in dynamic interaction analyses of structure–pile–soil systems in the time or the frequency domains. Usual practice relies on pseudo static formulations and a simplified alternative to include P–Y curves in this kind of analysis is also proposed, which is essentially the same as the dynamic ones but does not include radiation or hysteretical damping. 相似文献
20.
When deriving velocity models by forward modelling or inverting travel time arrivals from seismic refraction data, a heterogeneous but isotropic earth is usually assumed. In regions where the earth is not isotropic at the scale at which it is being sampled, the assumption of isotropy can lead to significant errors in the velocities determined for the crust and the depths calculated to reflecting boundaries. Laboratory velocity measurements on rocks collected from the Haast Schist terrane of South Island, New Zealand, show significant (up to 20%) compressional (P) wave velocity anisotropy. Field data collected parallel and perpendicular to the foliation of the Haast Schist exhibit as much as 11% P-wave velocity anisotropy. We demonstrate, using finite-difference full-wavefield modelling, the types of errors and problems that might be encountered if isotropic methods are used to create velocity models from data collected in anisotropic regions. These reflector depth errors could be as much as 10–15% for a 10-km thick layer with significant (20%) P-wave velocity anisotropy. The implications for South Island, New Zealand, where the problem is compounded by extreme orientations of highly anisotropic rocks (foliation which varies from horizontal to near vertical), are considered. Finally, we discuss how the presence of a significant subsurface anisotropic body might manifest itself in wide-angle reflection/refraction and passive seismic datasets, and suggest ways in which such datasets may be used to determine the presence and extent of such anisotropic bodies. 相似文献