Waveform inversion for localized seismic structure and an applications to D" structure beneath the
Waveform inversion for localized seismic structure and an applications to D" structure beneath the
复制标题
局部地震结构波形反演及其在地下D"结构中的应用
DOI：
10.1029/2009jb006503
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
and R.J. Geller
中科院分区：
文献类型：
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作者：
Kawai;K.;and R.J. Geller
为了从观测的地震数据中提取更多有关局部地震结构的信息，我们开发并应用了一种新的波形反演方法。合成地震图及其偏导数的计算是这种反演的关键步骤。我们制定了局部结构波形反演的反演问题，计算特定深度或空间点处的一维和三维各向异性弹性模量的偏导数。我们的方法在计算合成及其偏导数时不使用任何大圆近似。在这项研究中，我们使用周期范围为 8-200 秒的宽带波形的横向分量来反演太平洋下方最下地幔中剪切速度的垂直依赖性。我们发现，在核幔边界（CMB）上方 400 至 500 公里和 300 至 400 公里的区域，速度分别降低和增加 1% 至 1.5%。此外，我们发现CMB上方100至200公里和0至100公里的区域速度分别增加和减少0.5%至1%。这被解释为钙钛矿和后钙钛矿之间相变的证据（尽管不能排除化学分层模型）。
In order to extract more information on localized seismic structure from observed seismic data, we have developed and applied a new method of waveform inversion. The calculation of synthetic seismograms and their partial derivatives is the key steps in such an inversion. We formulate the inverse problem of waveform inversion for localized structure, computing partial derivatives for the 1‐D and 3‐D anisotropic elastic moduli at particular depth or at points in space. Our method does not use any great circle approximations in computing the synthetics and their partial derivatives. In this study we invert for the vertical dependence of the shear velocity in the lowermost mantle beneath the Pacific using the transverse component of broadband waveforms for the period range 8–200 s. We find 1%–1.5% velocity decreases and increases in the zones from 400 to 500 km and from 300 to 400 km above the core‐mantle boundary (CMB), respectively. In addition, we find 0.5%–1% velocity increases and decreases in the zones from 100 to 200 km and from 0 to 100 km above the CMB, respectively. This is interpreted as evidence for phase transitions between perovskite and postperovskite (although a chemical stratification model cannot be excluded).