The influence of nonuniform ambient noise on crustal tomography in Europe
The influence of nonuniform ambient noise on crustal tomography in Europe
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DOI：
10.1002/ggge.20081
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发表时间：
2013-05
期刊：
影响因子：
3.7
通讯作者：
P. Basini;T. Nissen‐Meyer;L. Boschi;Emanuele Casarotti;J. Verbeke;Olaf Schenk;Domenico Giardini
中科院分区：
文献类型：
--
作者：
P. Basini;T. Nissen‐Meyer;L. Boschi;Emanuele Casarotti;J. Verbeke;Olaf Schenk;Domenico Giardini
环境噪声地震学与高分辨率地壳成像密切相关，因为它在地震活动很少的地区提供了前所未有的密集数据覆盖。在均匀分布噪声源的假设下，它已被用来提取两个接收器之间的格林函数。我们通过现实 3D 地球模型中的波传播和伴随方法来确定这一假设的印记。在这种情况下，我们量化了来自中欧的环境噪声互相关相对于噪声源位置和剪切波速度结构的敏感性。我们使用 196 个站点一年多来记录的环境噪声，生成了包含 864 个互相关的数据库。我们的网格是基于地壳和 3D 断层扫描模型的组合构建的。我们使用 3D 谱元素方法模拟不同频带中的合成环境噪声互相关。这些不同频段中的走时互相关测量定义了合成与观测之间的失配，作为使用伴随方法计算灵敏度核的基础。我们对欧洲海域的不同地理位置和噪声源分布进行了全面分析。确定性敏感性分析可以估计起始地壳模型显示的位置与我们的数据集更好地相符，并深入了解欧洲地区噪声源的分布。这凸显了考虑层析成像的局部噪声分布的潜在重要性，并形成了层析成像反演的基础，其中噪声源的分布可以被视为类似于地震层析成像的自由参数。
Ambient‐noise seismology is of great relevance to high‐resolution crustal imaging, thanks to the unprecedented dense data coverage it affords in regions of little seismicity. Under the assumption of uniformly distributed noise sources, it has been used to extract the Green's function between two receivers. We determine the imprint of this assumption by means of wave propagation and adjoint methods in realistic 3‐D Earth models. In this context, we quantify the sensitivity of ambient‐noise cross‐correlations from central Europe with respect to noise‐source locations and shear wave‐speed structure. We use ambient noise recorded over 1 year at 196 stations, resulting in a database of 864 cross‐correlations. Our mesh is built upon a combined crustal and 3‐D tomographic model. We simulate synthetic ambient‐noise cross‐correlations in different frequency bands using a 3‐D spectral‐element method. Traveltime cross‐correlation measurements in these different frequency bands define the misfit between synthetics and observations as a basis to compute sensitivity kernels using the adjoint method. We perform a comprehensive analysis varying geographic station and noise‐source distributions around the European seas. The deterministic sensitivity analysis allows for estimating where the starting crustal model shows better accordance with our data set, and gain insight into the distribution of noise sources in the European region. This highlights the potential importance of considering localized noise distributions for tomographic imaging, and forms the basis of a tomographic inversion in which the distribution of noise sources may be treated as a free parameter similar to earthquake tomography.