Current seismic tomography models show a complex environment underneath the crust, corroborated by high-precision satellite gravity observations. Both data sets are used to independently explore the density structure of the upper mantle. However, combining these two data sets proves to be challenging. The gravity-data has an inherent insensitivity in the radial direction and seismic tomography has a heterogeneous data acquisition, resulting in smoothed tomography models with de-correlation between different models for the mid-to-small wavelength features. Therefore, this study aims to assess and quantify the effect of regularization on a seismic tomography model by exploiting the high lateral sensitivity of gravity data. Seismic tomography models, SL2013sv, SAVANI, SMEAN2 and S40RTS are compared to a gravity-based density model of the upper mantle. In order to obtain similar density solutions compared to the seismic-derived models, the gravity-based model needs to be smoothed with a Gaussian filter. Different smoothening characteristics are observed for the variety of seismic tomography models, relating to the regularization approach in the inversions. Various S40RTS models with similar seismic data but different regularization settings show that the smoothening effect is stronger with increasing regularization. The type of regularization has a dominant effect on the final tomography solution. To reduce the effect of regularization on the tomographymodels, an enhancement procedure is proposed. This enhancement should be performed within the spectral domain of the actual resolution of the seismic tomography model. The enhanced seismic tomography models show improved spatial correlationwith each other and with the gravity-based model. The variation of the density anomalies have similar peak-to-peak magnitudes and clear correlation to geological structures. The resolvement of the spectral misalignment between tomographic models and gravity-based solutions is the first step in the improvement of multidata inversion studies of the upper mantle and benefit from the advantages in both data sets.

中文翻译：

---

比较全球断层扫描和基于重力的上地幔密度模型

当前的地震层析成像模型显示了地壳下的复杂环境，高精度卫星重力观测证实了这一点。两个数据集都用于独立探索上地幔的密度结构。然而，结合这两个数据集被证明是具有挑战性的。重力数据在径向具有固有的不敏感性，而地震层析成像具有异构数据采集，导致平滑层析成像模型在中小波长特征的不同模型之间具有去相关性。因此，本研究旨在通过利用重力数据的高横向敏感性来评估和量化正则化对地震层析成像模型的影响。将地震断层扫描模型 SL2013sv、SAVANI、SMEAN2 和 S40RTS 与基于重力的上地幔密度模型进行比较。为了获得与地震衍生模型相似的密度解，需要使用高斯滤波器对基于重力的模型进行平滑处理。对于各种地震层析成像模型，观察到不同的平滑特性，这与反演中的正则化方法有关。具有相似地震数据但不同正则化设置的各种 S40RTS 模型表明，随着正则化的增加，平滑效果更强。正则化的类型对最终的断层扫描解决方案有主要影响。为了减少正则化对断层扫描模型的影响，提出了一种增强程序。这种增强应该在地震层析成像模型的实际分辨率的谱域内进行。增强型地震层析成像模型显示出相互之间以及与基于重力模型的空间相关性得到改善。密度异常的变化具有相似的峰峰值和与地质结构的明显相关性。解决层析成像模型和基于重力的解决方案之间的光谱错位是改进上地幔多数据反演研究的第一步，并受益于这两个数据集的优势。