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Published December 28, 2019 | Published + Supplemental Material
Journal Article Open

Frequency-Dependent P Wave Polarization and Its Subwavelength Near-Surface Depth Sensitivity

Abstract

Near‐surface structure is crucial to assessing seismic hazards and understanding earthquakes and surface processes yet is a major challenge to robustly image. Recently, an approach based on body‐wave polarization was introduced for constraining shallow seismic structure, but the depth sensitivity of the polarization measurement has remained unclear. Using waveform simulations based on a layer over a half space, we find that the depth sensitivity of P wave polarization peaks at the surface and decreases abruptly over a depth range shorter than its wavelength. A strong frequency dependence provides constraints on local 1‐D structure, with frequencies between 0.1 and 10 Hz illuminating structure at depths of 10 m to several kilometers. Applying these results to teleseismic recordings in Japan provides constraints on structure at about 120 to 750 m, including a distinctive weak zone along the Median Tectonic Line in the Kii peninsula and Awaji Island.

Additional Information

© 2019 American Geophysical Union. Received 9 AUG 2019; Accepted 8 NOV 2019; Accepted article online 15 NOV 2019. The authors thank the editor Jeroen Ritsema and two anonymous reviewers for helpful comments. S.P. thanks Hiroo Kanamori for valuable discussion about the Median Tectonic Line. The early phase of this work was supported by NSF grant EAR‐1735960. S. P. was also supported by the Caltech Texaco Postdoctoral Fellowship. The waveform simulation code was obtained from QUEST (http://www.quest‐itn.org/library/software/reflectivity‐method.html).

Attached Files

Published - Park_et_al-2019-Geophysical_Research_Letters.pdf

Supplemental Material - grl59862-sup-0001-2019gl084892-si.docx

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