Abstract:

First, SS precursor boundary sensitivity kernel is calculated based on finite-frequency theory and the sensitivity of SS precursor traveltime perturbation to the topography perturbation implemented on mantle discontinuity is analysed. Next, SS precursor waveform with topography perturbation implemented on mantle discontinuity is simulated using SPECFEM and its traveltime perturbation is measured and compared with the traveltime perturbation predicted by finite-frequency theory. It is found that finite-frequency theory can well explain the wavefront healing effect of SS precursor. At last, an inversion scheme is built based on boundary sensitivity kernel, and more reliable topography of the mantle discontinuity can be obtained after considering the finite-frequency effect of SS precursor. This research provides some preliminary knowledge for inversion of the topography of mantle discontinuities using SS precursor.

Key words: SS precursor, mantle discontinuity, transition zone, finite frequency, ray theory

摘要：

首先, 根据有限频原理计算SS前驱震相的边界敏感核, 分析SS前驱震相对间断面起伏状况的敏感性。然后, 利用SPECFEM软件正演间断面存在起伏扰动下的SS前驱震相波形, 得到其到时扰动量, 与利用有限频敏感核计算得到的到时扰动量相比较, 说明有限频理论可以较好地解释SS前驱震相的波前愈合效应。最后, 利用边界敏感核反演界面起伏状况, 展示当考虑SS前驱震相的有限频效应时, 可以更好地恢复界面起伏的真实状况。研究结果为正确利用SS前驱震相反演地幔间断面起伏提供了必要的基础。

关键词: SS 前驱震相, 地幔间断面, 转换带, 有限频, 射线理论