Inferring earth structure from combined measurements of rotational and translational ground motions
Inferring earth structure from combined measurements of rotational and translational ground motions
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DOI：
10.1190/1.3211110
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发表时间：
2009-11-01
期刊：
影响因子：
3.3
通讯作者：
Igel, Heiner
中科院分区：
文献类型：
--
作者：
Bernauer, Moritz;Fichtner, Andreas;Igel, Heiner
我们介绍了一种新的变形地震层析成像的基础上共定位测量的旋转和平移地面运动。我们的目的是评估旋转是否可以成功地纳入地震反演问题，以产生更好的解决和更逼真的层析图像。我们的方法是基于视S波速度的定义为均方根速度和旋转振幅的比值。这个定义的主要优点是：（1）不需要走时测量;（2）视横波速度与震源震级和震源定时无关。我们推导出有限频率核的视S波速度通过使用伴随方法和射线近似相结合。这些核的特性作为频率带宽的函数，可以沿着说明它们对于地震层析成像的有用性。在多频合成反演中，我们考虑了局部井间层析成像和区域尺度地震层析成像。我们的研究结果表明，S波速度的变化可以准确地从同位旋转和平移测量，这表明我们的方法是一个很有前途的扩展传统的地震层析成像。此外，表观S波速度可以用于增加局部结构的地震层析成像中的垂直分辨率。
We introduce a novel variant of seismic tomography that is based on colocated measurements of rotational and translational ground motions. Our aim is to assess whether rotations may be incorporated successfully into seismic inverse problems to produce better resolved and more realistic tomographic images. Our methodology is based on the definition of apparent S-wave speed as the ratio of rms velocity and rotation amplitudes. The principal advantages of this definition are that (1) no traveltimes measurements are needed and (2) the apparent S-wave speed is independent of source magnitude and source timing. We derive finite-frequency kernels for apparent S-wave speed by using a combination of the adjoint method and ray approximation. The properties of these kernels as a function of frequency bandwidth can be illustrated along with their usefulness for seismic tomography. In multifrequency synthetic inversions, we consider local cross-hole tomography and regional-scale earthquake tomography. Our results indicate that S-wave speed variations can be retrieved accurately from colocated rotation and translation measurements, suggesting that our methodology is a promising extension of conventional seismic tomography. Further, apparent S-wave speed can be used to increase vertical resolution in teleseismic tomography for local structures.