...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Pure and Applied Geophysics >Wavenumber Sampling Issues in 2.5D Frequency Domain Seismic Modelling
【24h】

Wavenumber Sampling Issues in 2.5D Frequency Domain Seismic Modelling

机译：2.5D频域地震建模中的波数采样问题

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

There are several important wavenumber sampling issues associated with 2.5D seismic modelling in the frequency domain, which need careful attention if accurate results are to be obtained. At certain critical wavenumbers there exist rapid disruptions in the mainly smooth oscillatory spectra. The amplitudes of these disruptions can be very large, and this affects the accuracy of the inverse Fourier transformed frequency-space domain solution. In anisotropic elastic media there are critical wavenumbers associated with each wave mode—the quasi-P (qP) wave, and the two quasi-shear (qS1 and qS2) waves. A small wavenumber sampling interval is desirable in order to capture the highly oscillatory nature of the wavenumber spectrum, especially at increasing distance from the source. Obviously a small wavenumber sampling interval adds greatly to the computational effort because a 2D problem must be solved for every wavenumber and every frequency. The discretisation should be carried out up to some maximum wavenumber, beyond which the field becomes evanescent (exponentially decaying or diffusive). For receivers close to the source, activity persists beyond the critical wavenumber associated with the minimum shear wave velocity in the model. Fortunately, for receivers well removed from the source, the contribution from the evanescent energy is negligible and so there is no need to sample beyond this critical wavenumber. Sampling at Gauss–Legendre spacings is a satisfactory approach for acoustic media, but it is not practical in elastic media due to the difficulty of partitioning the integration around the different critical wavenumbers. We found to our surprise that in transversely isotropic media, the critical wavenumbers are independent of wave direction, but always occur at those wavenumbers corresponding to the maximum phase velocities of the three wave modes (qP, qS1 and qS2), which depend only on the elastic constants and the density. Additionally, we have observed that intermediate layers between source and receiver can filter out to a large degree, the sharp irregularities around the critical wavenumbers in the ω–k y spectra. We have found that, using the spectral element method, the singularities (poles) at the critical wavenumbers which exist with analytic solutions, do not arise. However, the troublesome spike-like behaviour still occurs and can be damped out without distorting the spectrum elsewhere, through the introduction of slight attenuation.
机译：在频域中，与2.5D地震建模相关的几个重要波数采样问题，如果要获得准确的结果，则需要仔细注意。在某些临界波数处，主要是光滑的振荡频谱中存在快速破坏。这些干扰的幅度可能非常大，这会影响傅立叶逆变换的频空域解的准确性。在各向异性弹性介质中，与每种波模式相关的临界波数为准P（qP）波和两个准剪切（qS1和qS2）波。为了捕获波数频谱的高度振荡特性，尤其是在距声源的距离越来越大的情况下，需要一个小的波数采样间隔。显然，小波数采样间隔大大增加了计算工作量，因为必须为每个波数和每个频率解决二维问题。离散化应进行到某个最大波数，超过该最大波数，场将消失（呈指数衰减或扩散）。对于靠近源的接收器，活动持续超过与模型中最小剪切波速度相关的临界波数。幸运的是，对于远离源头的接收器而言，e逝能量的贡献可忽略不计，因此无需采样超过此临界波数。对于声学介质，以高斯-勒格德勒间距采样是一种令人满意的方法，但由于难以在不同的临界波数附近划分积分，因此在弹性介质中不可行。我们惊讶地发现，在横观各向同性的介质中，临界波数与波的方向无关，但始终出现在与三个波模（qP，qS1和qS2）的最大相速度相对应的那些波数上，后者仅取决于弹性常数和密度。此外，我们已经观察到，源和接收器之间的中间层可以在很大程度上过滤掉ω-ky 谱中关键波数周围的尖锐不规则性。我们发现，使用频谱元素方法，不会出现解析解中存在的临界波数的奇点（极点）。但是，麻烦的尖峰状行为仍然会发生，并且可以通过引入轻微的衰减来衰减而不会使其他地方的频谱失真。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号