Constraints on earthquake epicentres independent of seismic velocity models   总被引：1，自引：0，他引：1  

T. Nicholson  Ó. Gudmundsson  M. Sambridge 《Geophysical Journal International》2004,156(3):648-654

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地震波走时计算的逆风差分算法   总被引：5，自引：0，他引：5  

熊金良  李国发  王濮  何兵寿 《物探化探计算技术》2004,26(4):295-298

快速精确地旅行时计算在地震资料的叠前偏移与层析反演中起重要作用。利用逆足差分格式求解程函方程，首先在波阵面上寻找全局极小点，然后计算该点周围各点的地震波初至走时，同时，采用局部算法以确保计算的稳定性。该算法对于任意复杂地质模型都具有较高的精度。  相似文献   

共聚焦点道集偏移速度建模   总被引：3，自引：1，他引：3  

李振春  穆志平  张建磊  张凯  王延光  陈世军 《物探与化探》2003,27(5):403-406,410

偏移速度建模可在多种道集实现.基于等时原理和差异时移分析,提出了共聚焦点道集偏移速度建模方法.偏移速度的更新是利用约束参数迭代反演实现,模型的参数化主要依据实际情况而定.为适应横向变速,选用了垂直速度梯度参数.模型试算表明:偏移速度相对误差在0.25%范围内,反射层深度误差小于10m.  相似文献   

Traveltimes of waves in three-dimensional random media   总被引：4，自引：0，他引：4  

A. M. Baig  F. A. Dahlen  S.-H. Hung 《Geophysical Journal International》2003,153(2):467-482

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Irregular interface parametrization in 3-D wide-angle seismic traveltime tomography   总被引：1，自引：0，他引：1  

N. Rawlinson  M. Sambridge 《Geophysical Journal International》2003,155(1):79-92

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测井资料解释煤成气层方法研究   总被引：10，自引：1，他引：9  

潘和平  黄智辉 《现代地质》1994,8(1):119-125

本文在应用计算机对测井曲线进行分层的基础上,利用孔隙差异法、声波差值法、空间模量差比法和电阻率比值法逐层综合解释煤成气层,并对这几种方法在解释煤成气层时可能出现的问题进行了探讨．  相似文献   

Finite difference calculation of traveltime on non-orthogonal grid          下载免费PDF全文

Xiangfang Zeng  Sidao Ni 《地震科学（英文版）》2018,31(2):55-61

Finite difference methods have been widely employed in solving the eikonal equation so as to calculate traveltime of seismic phase. Most previous studies used regular orthogonal grid. However, much denser grid is required to sample the interfaces that are undulating in depth direction, such as the Moho and the 660 km discontinuity.Here we propose a new finite difference algorithm to solve the eikonal equation on non-orthogonal grid(irregular grid).To demonstrate its efficiency and accuracy, a test was conducted with a two-layer model. The test result suggests that the similar accuracy of a regular grid with ten times grids could achieve with our new algorithm, but the time cost is only about 0.1 times. A spherical earth model with an undulant660 km discontinuity was constructed to demonstrate the potential application of our new method. In that case, the traveltime curve fluctuation corresponds to topography. Our new algorithm is efficient in solving the first arrival times of waves associated with undulant interfaces.  相似文献   

3D P‐wave traveltime computation in transversely isotropic media using layer‐by‐layer wavefront marching          下载免费PDF全文

Jiangtao Hu  Junxing Cao  Huazhong Wang  Xingjian Wang  Renfei Tian 《Geophysical Prospecting》2018,66(7):1303-1314

Subsurface rocks (e.g. shale) may induce seismic anisotropy, such as transverse isotropy. Traveltime computation is an essential component of depth imaging and tomography in transversely isotropic media. It is natural to compute the traveltime using the wavefront marching method. However, tracking the 3D wavefront is expensive, especially in anisotropic media. Besides, the wavefront marching method usually computes the traveltime using the eikonal equation. However, the anisotropic eikonal equation is highly non‐linear and it is challenging to solve. To address these issues, we present a layer‐by‐layer wavefront marching method to compute the P‐wave traveltime in 3D transversely isotropic media. To simplify the wavefront tracking, it uses the traveltime of the previous depth as the boundary condition to compute that of the next depth based on the wavefront marching. A strategy of traveltime computation is designed to guarantee the causality of wave propagation. To avoid solving the non‐linear eikonal equation, it updates traveltime along the expanding wavefront by Fermat's principle. To compute the traveltime using Fermat's principle, an approximate group velocity with high accuracy in transversely isotropic media is adopted to describe the ray propagation. Numerical examples on 3D vertical transverse isotropy and tilted transverse isotropy models show that the proposed method computes the traveltime with high accuracy. It can find applications in modelling and depth migration.  相似文献   

数据域初至波走时与成像域反射波走时联合层析速度建模方法          下载免费PDF全文

张兵  王华忠 《地球物理学报》2019,62(7):2633-2644

复杂地表探区,尤其是盆山过渡区的油气勘探是我国也是世界上油气勘探的重点区域,但是此类区域油气地震勘探中满足精确地震成像的速度建模一直是个没有很好解决的问题.本文提出了一种综合性的数据域初至波走时与成像域反射波走时联合层析复杂地表浅中深层速度建模方法,并针对联合层析速度反演解的非唯一性问题,深入地分析了层析反演中正则化的本质意义,指出了建立构造特征正则化方法的具体技术路线,提出了联合层析的实现流程及策略.理论和实际数据试验表明,本文提出的数据域初至走时与成像域反射走时联合层析浅中深层速度建模技术避免了常规建模方法中浅层速度模型与中深层速度模型的融合问题,较好地解决了传统成像域反射层析对近地表模型的不可控更新问题,整体提升了深度域浅中深层速度模型的建模精度,进而提高了复杂地表、复杂构造区的地震成像质量.  相似文献   

Traveltime approximation in vertical transversely isotropic layered media          下载免费PDF全文

Igor Ravve  Zvi Koren 《Geophysical Prospecting》2017,65(6):1559-1581

The well‐known asymptotic fractional four‐parameter traveltime approximation and the five‐parameter generalised traveltime approximation in stratified multi‐layer transversely isotropic elastic media with a vertical axis of symmetry have been widely used for pure‐mode and converted waves. The first three parameters of these traveltime expansions are zero‐offset traveltime, normal moveout velocity, and quartic coefficient, ensuring high accuracy of traveltimes at short offsets. The additional parameter within the four‐parameter approximation is an effective horizontal velocity accounting for large offsets, which is important to avoid traveltime divergence at large offsets. The two additional parameters in the above‐mentioned five‐parameter approximation ensure higher accuracy up to a given large finite offset with an exact match at this offset. In this paper, we propose two alternative five‐parameter traveltime approximations, which can be considered extensions of the four‐parameter approximation and an alternative to the five‐parameter approximation previously mentioned. The first three short‐offset parameters are the same as before, but the two additional long‐offset parameters are different and have specific physical meaning. One of them describes the propagation in the high‐velocity layer of the overburden (nearly horizontal propagation in the case of very large offsets), and the other characterises the intercept time corresponding to the critical slowness that includes contributions of the lower velocity layers only. Unlike the above‐mentioned approximations, both of the proposed traveltime approximations converge to the theoretical (asymptotic) linear traveltime at the limit case of very large (“infinite”) offsets. Their accuracy for moderate to very large offsets, for quasi‐compressional waves, converted waves, and shear waves polarised in the horizontal plane, is extremely high in cases where the overburden model contains at least one layer with a dominant higher velocity compared with the other layers. We consider the implementation of the proposed traveltime approximations in all classes of problems in which the above‐mentioned approximations are used, such as reflection and diffraction analysis and imaging.  相似文献