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Marijan Herak Davorka Herak 《CT理论与应用研究》2008,17(3):18-26
克罗地亚地球物理学家莫霍洛维奇在研究1909年10月8日克罗地亚地震的地震波走时特征时,首次发现了该地区的地壳与地幔的分界面,后被命名“莫霍界面”,简称Moho界面。1927年,莫霍洛维奇又在地震记录中识别出了S^＊震相,证实了在地壳内部还会存在另一个康拉德（Conrad）间断面。地震层析成像是研究地球内部结构的重要方法之一。为纪念莫霍洛维奇诞生150周年,莫霍界面发现100周年,特发此文,以兹纪念。 相似文献
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编者按:克罗地亚地球物理学家莫霍洛维奇在研究1909年10月8日克罗地亚地震的地震波走时特征时,首次发现了该地区的地壳与地幔的分界面,后被命名"莫霍界面",简称Moho界面.1927年,莫霍洛维奇又在地震记录中识别出了s*震相,证实了在地壳内部还会存在另一个康拉德(Conrad)间断面.地震层析成像是研究地球内部结构的重要方法之一.为纪念莫霍洛维奇诞生150周年,莫霍界面发现100周年,特发此文,以兹纪念. 相似文献
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美国《地震情报通报》1980年第12卷3期登载一篇介绍《安德里雅·莫霍洛维奇》的署名文章,摘译如下:安德里雅·莫霍洛维奇生前是南斯拉夫萨格勒布气象台台长和萨格勒布大学教授。莫霍洛维奇研究地震资料发现,在地球内部约50公里的深处地震波随深度而增加。他识 相似文献
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一、引言 地壳和上地幔顶部的构造,对研究地震发生、发展及演变过程的深部背景,以及划分地震活动块体和探讨地震成因有着重要的意义。然而地壳构造的研究,又是与地震学的发展密切相关。1909年,莫霍洛维奇在近震研究中,首先发现了地壳与上地幔分界面的首波,其覆盖层的平均速度 =6.3公里/秒,界面速度Vd=8.0公里/秒（简称M界面）。后于1923年,康拉德（conrad）也是根据天然地震资料鉴别出一个平均速度为=5.4 相似文献
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空气或風化了的地表层具有較小的波阻抗,其下則为具有較高波阻抗的致密介質,因而地表面或低速带的底面是两个波阻抗数值相差悬殊的介質的分界面。当地震波入射到这样的一个分界面上时,就有可能产生反射波。这种情况在天然地震（此时,首次的反射系来自地表面）以及勘探地震的实际工作中是会碰到的。 相似文献
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肖承邺 《地震地磁观测与研究》1984,(4)
地球物理学家莫霍洛维奇是南斯拉夫人,1857年1月出生在南斯拉夫沃洛斯科的克罗小海港。莫霍洛维奇年轻时在布拉格大学攻读数学和物理,毕业后任教于巴卡尔海运学校,并在那里建立了一个气象台。年被1891任命为萨格勒布气象台台长,兼任萨格勒布大学教授。 相似文献
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水合物地震属性研究的一个基本目标是水合物/游离气含量的估算. 这项工作的难度体现在地震反演具有多解性. 这项工作涉及到地震数据的精细处理、速度分析和BSR界面AVO分析等多个具体环节. 本文继承前人的有关成果,尝试进行了水合物/游离气含量估算方法的研究. 以区域地质、地震和化探等多元方法信息为基础,以定性推断BSR以及BSR界面AVO性质为导向,通过AVO正演模型方法,半定量（或定量）地估算BSR界面上与下地层中水合物/游离气（或水合物/水合物）的含量. 运用这种方法,结合海上有利于天然气水合物的E研究区某测线地震资料,尝试估算了BSR界面之上和之下介质中水合物/游离气的含量. 相似文献
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一般工程的地震反应分析中地震波假设为竖直向上入射的体波,场地自由波场可简化为成层半空间模型的一维波动问题,通过数值方法获得出平面自由场。在数值计算方法中以显式有限差分法为代表的时间域方法是当前地震波模拟的主流方法,其精度通常受到计算方法、模型尺寸、网格大小、边界设定等诸多条件的影响,数值算法稳定性还受到许多计算参数的限制。为了改进时域数值方法中存在的这些缺点和不足,本文结合分层均匀介质中的理论地震图合成方法提出了一种新的时域数值算法。其基本思想是将计算节点直接设置在波阻抗界面处,各个层内不再设置计算节点,然后根据地震波在波阻抗界面处的反射、透射关系及其在相邻界面之间的传播时间建立计算界面节点振动的数学表达式,据此计算得到各层界面节点的振动,并通过对自由面节点进行适当处理得到成层半空间出平面自由场。界面节点振动可看作为入射波通过波阻抗界面处产生的次一级子波源,本文称之为界面子波,因此把这一计算方法称为界面子波算法。数值算例表明该方法具有很高的精度和很快的计算效率。理论上还可将这一方法推广至二维波动情形,即地震波倾斜入射条件下成层半空间出平面自由场的计算。 相似文献
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《中国地震研究》2021,(1)
Accurate calculations of travel times and raypaths of reflection waves are important for reflection travel time tomography. The multistage shortest path method(MSPM) and multistage fast marching method(MFMM) have been widely used in reflection wave raytracing, and both of them are characterized by high efficiency and accuracy. However, the MSPM does not strictly follow Snell's law at the interface because it treats the interface point as a sub-source, resulting in a decrease in accuracy. The MFMM achieves high accuracy by solving the Eikonal equation in local triangular mesh. However, the implementation process is complex. Here we propose a new method which uses linear interpolation to compute the incident travel time of interface points and then using Snell's law to compute the reflection travel time of grid points just above the interface. Our new method is much simpler than the MFMM; furthermore, numerical simulations show that the accuracy of the MFMM and our new method are basically the same, thus the reflection tomography algorithms which use our new method are easier to implement without decreasing accuracy. Besides, our new method can be extended easily to other grid-based raytracing methods. 相似文献
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本文在各向同性介质假设下,计算了薄层顶、底反射P波和PS波的理论地震图.理论模拟发现薄层的反射P波与PS波是一复合波,包括层内的多次透射和反射转换波型,且具有类似单一界面反射的、脉冲式的波形特征.两类薄层反射整体振幅随着薄层厚度的降低而缩小;在地震子波主频40 Hz条件下,2 m左右厚度的薄层反射相比单一界面反射具有等同的振幅水平.1 m以下极薄层仅有弱反射甚至无反射;薄层反射复合波振幅与炮检距的关系依然成立,但不惟一;单界面反射AVO原理、方法不适用于薄层反射解释与反演. 相似文献
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Summary In areas of steeply dipping seismic horizons, the conventional split-spread seismic reflection method may yield poor seismograms. In order to develop a suitable field technique to improve the record quality in such areas, an analysis of the effect of spherical divergence, reflection coefficient, and absorption on the amplitude of the signal reflected from a dipping interface has been carried out. It has been found that for a dipping interface the reflected signal amplitude in many cases may be higher for the larger angles of incidence at the reflecting bed than for the normal incidence. Thus, a suitable inline-offset spread in the updip direction is likely to increase the recorded reflected signal amplidute and improve the signal-to-noisre ratio in areas of dipping reflectors. The design of such a shot-spread configuration has been developed in this paper, and a field method using this configuration is suggested for continuous mapping of subsurface horizons. 相似文献
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EXPLORATION OF UNDERWATER THREE-DIMENSIONAL TOPOGRAPHY AND ACTIVE FAULTS: A CASE STUDY OF QIONGHAI,XICHANG 
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下载免费PDF全文 CAI Ming-gang LU Ren-qi HE Hong-lin XU Xi-wei WANG Zhen-nan LI Hai-ou WU Xi-yan 《地震地质》2018,40(1):204-214
The theories, techniques and methods for the exploration of active faults in the terrestrial domain are relatively mature, while such efforts in the water domain remain very few. In this study, the AAE shallow profiler was used to detect the underwater three-dimensional topography and active faults in the Qionghai area, Xichang for the first time. Based on the SKUA-GOCAD software platform and its DSI interpolation method, three-dimensional modeling of the exploration data was carried out. The survey profiles clearly reveal three different reflection interfaces, including the underwater interface, the interface between the silt layer and shallow sedimentary layer, and the bottom of the shallow sedimentary layer. The three-dimensional topography of the Qionghai area was mapped initially. Moreover, evidence of active faults was first found in several survey profiles from the reflection interface cutoff. This study also analyzed and discussed the working principle and characteristics of the AAE shallow profiler, including their parameters and various factors of exploration. The mapped three-dimensional topography and active faults in the Qionghai area of Xichang can provide a reference for research on the active tectonics underwater in the future. 相似文献
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光滑处理使得单界面成为非均匀薄层,界面反射转变为层反射.为了探讨光滑处理的影响,以平面波作为入射波场,首先利用过渡层反射系数推导了反射信号的理论公式,然后就非均匀薄层下反射系数的计算问题,给出了具体的实现算法,并通过与经典Epstein过渡层反射系数解析结果的对比说明了算法的精度.最后在单界面及其被光滑后界面的对比分析中,得出了几点重要结论：随着光滑次数的增加,反射信号的到时基本保持不变,而反射信号的主频与能量呈减少趋势,其中信号能量在低光滑次数的衰减速率明显大于高光滑次数. 相似文献
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利用横波响应进行裂缝性各向异性介质的检测在实际应用中取得了很好的效果,但技术复杂、成本较高使该方法的广泛使用受到限制,而纵波资料采集和处理技术的精细有效保持了纵波的各种属性,这为直接利用纵波资料进行裂缝检测创造了条件.地下垂直定向裂缝通常用HTI介质模型来描述,为此,本文利用射线追踪和反射率法计算了层状各向同性介质背景下的HTI介质顶、底界面的反射纵波旅行时和反射系数,并分析了这些属性随观测方位的变化规律.研究表明,HTI介质底界面反射纵波旅行时和HTI介质顶界面反射系数表现出了明显的方位各向异性;旅行时、振幅和AVO梯度属性均在0°观测方位和90°观测方位上存在最大差异,可以用多种属性联合来精确判定裂缝的发育方向. 相似文献
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In this paper, we propose a hybrid PML (H-PML) combining the normal absorption factor of convolutional PML (C-PML) with tangential absorption factor of Mutiaxial PML (M-PML). The H-PML boundary conditions can better suppress the numerical instability in some extreme models. and the computational speed of finite-element method and the dynamic range are greatly increased using this HPML. We use the finiteelement method with a hybrid PML to model the acoustic reflection of the interface when wireline and well logging while drilling (LWD), in a formation with a reflector outside the borehole. The simulation results suggests that the PS- and SP- reflected waves arrive at the same time when the inclination between the well and the outer interface is zero, and the difference in arrival times increases with increasing dip angle. When there are fractures outside the well, the reflection signal is clearer in the subsequent reflection waves and may be used to identify the fractured zone. The difference between the dominant wavelength and the model scale shows that LWD reflection logging data are of higher resolution and quality than wireline acoustic reflection logging. 相似文献
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Based on knowledge of a commutative group calculation of the rock stiffness and on some geophysical assumptions, the simplest fractured medium may be regarded as a fracture embedded in an isotropic background medium, and the fracture interface can be simulated as a linear slip interface that satisfies non‐welded contact boundary conditions: the kinematic displacements are discontinuous across the interface, whereas the dynamic stresses are continuous across the interface. The finite‐difference method with boundary conditions explicitly imposed is advantageous for modelling wave propagation in fractured discontinuous media that are described by the elastic equation of motion and non‐welded contact boundary conditions. In this paper, finite‐difference schemes for horizontally, vertically, and orthogonally fractured media are derived when the fracture interfaces are aligned with the boundaries of the finite‐difference grid. The new finite‐difference schemes explicitly have an additional part that is different from the conventional second‐order finite‐difference scheme and that directly describes the contributions of the fracture to the wave equation of motion in the fractured medium. The numerical seismograms presented, to first order, show that the new finite‐difference scheme is accurate and stable and agrees well with the results of previously published finite‐difference schemes (the Coates and Schoenberg method). The results of the new finite‐difference schemes show how the amplitude of the reflection produced by the fracture varies with the fracture compliances. Later, comparisons with the reflection coefficients indicate that the reflection coefficients of the fracture are frequency dependent, whereas the reflection coefficients of the impedance contrast interface are frequency independent. In addition, the numerical seismograms show that the reflections of the fractured medium are equal to the reflections of the background medium plus the reflections of the fracture in the elastic fractured medium. 相似文献