期刊
GEOPHYSICAL JOURNAL INTERNATIONAL
卷 220, 期 2, 页码 996-1011出版社
OXFORD UNIV PRESS
DOI: 10.1093/gji/ggz479
关键词
Rotational seismology; Site effects; Theoretical seismology; Wave propagation
资金
- French National Research Agency [ANR-16-CE31-0022]
- European Research Council [339991]
- European Research Council (ERC) [339991] Funding Source: European Research Council (ERC)
Local small-scale heterogeneities, like geological inhomogeneities, surface topographies and cavities are known to affect seismic wavefield gradients. This effect is in fact measurable with current instruments. For example, the agreement between data and synthetics computed in a tomographic model is often not as good for rotation as it is for displacement. Here, we use the theory of homogenization to explain why small-scale heterogeneities strongly affect wavefield gradients, but not the wavefield itself. We show that at any receiver measuring wavefield gradient, small-scale heterogeneities cause the wavefield gradient to couple with strain through a coupling tensor J. Furthermore, we show that this J is (1) independent of source, (2) independent of time, but (3) only dependent on the receiver location. Consequently, we can invert for J based on an effective model for which synthetics fit displacement data reasonably well. Once inverted, J can be used to correct rotations at that receiver for other sources. Results of the correction are shown for synthetic rotational receivers and for the ring laser located in Wettzell, Germany. We find that compared to synthetics, the synthetics corrected through J are a better fit to the rotation data. Although results here are derived for rotations, they can be extended to receivers measuring any wavefield gradient.
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