Density is one of the most essential properties that determines the dynamic behavior of the Earth. Besides, density has been commonly used to investigate the mineral composition, porosity and fluid content of rock. Therefore, a reliable estimation of the density structure is one of the most important objectives in both global seismology and seismic exploration. However, seismic inversions of independent density estimates are ill-posed because density has a large trade-off with velocities. Shear wave propagation is sensitive to both density and the S-wave velocity. We show that the reflected SV-wave (SV-to-SV wave) at an incident angle of 22.5^o depends only on density contrast, and at incident angle 30^o it depends only on S-wave velocity contrast. Thus, density as well as S-wave velocity can be directly inverted from the reflected SV-wave as separate and independent parameters. The forward modelling has high accuracy, the inverse problem is well-posed and the misfit function can be easily regularized. Field data application demonstrates the proposed method can efficiently recover reliable and high-resolution density and S-wave velocity of fine sturctures. Thus, this method has great potential in geological interpretation including understanding regional Moho structure, crustal and mantle formation and evolution, and rock lithologic composition and fluid-filled porosity.

中文翻译：

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反射的SV波反演用于密度和S波速度结构

密度是决定地球动态行为的最重要属性之一。此外，密度通常用于研究岩石的矿物成分，孔隙率和流体含量。因此，对密度结构的可靠估算是全球地震学和地震勘探中最重要的目标之一。但是，独立密度估计的地震反演是不合适的，因为密度与速度之间存在很大的权衡。剪切波传播对密度和S波速度都敏感。我们表明，入射角为22.5 ^o时反射的SV波（SV到SV波）仅取决于密度对比，入射角为30 ^o时它仅取决于S波速度对比。因此，密度和S波速度可以直接作为独立和独立的参数从反射的SV波中反转。正向建模具有很高的精度，反问题很好，而且失配函数可以很容易地进行正则化。现场数据应用表明，该方法可以有效地恢复精细结构的可靠的高分辨率密度和S波速度。因此，该方法在地质解释方面具有很大的潜力，包括了解区域莫霍面构造，地壳和地幔的形成和演化以及岩石岩性成分和充满流体的孔隙度。