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Published October 16, 2017 | Published + Supplemental Material
Journal Article Open

Localized water reverberation phases and its impact on back-projection images


Coherent radiators imaged by backprojections (BP) are commonly interpreted as part of the rupture process. Nevertheless, artifacts introduced by structure related phases are rarely discriminated from the rupture process. In this study, we use a calibration event to discriminate between rupture and structure effects. We reexamine the waveforms and BP images of the 2012 M_w 7.2 Indian Ocean earthquake and a calibration event (M_w 6.2). The P wave codas of both events present similar shape with characteristic period of approximately 10 s, which are backprojected as coherent radiators near the trench. S wave BP does not image energy radiation near the trench. We interpret those coda waves as localized water reverberation phases excited near the trench. We perform a 2-D waveform modeling using realistic bathymetry model and find that the steep near-trench bathymetry traps the acoustic water waves forming localized reverberation phases. These waves can be imaged as coherent near-trench radiators with similar features as that in the observations. We present a set of methodologies to discriminate between the rupture and propagation effects in BP images, which can serve as a criterion of subevent identification.

Additional Information

© 2017 American Geophysical Union. Received 25 FEB 2017; Accepted 17 MAY 2017; Accepted article online 22 MAY 2017; Published online 3 OCT 2017. Data analysis and plotting made use of GMT and Matlab. The teleseismic data are recorded by GSN network and accessed through the IRIS data management center. F-net data are accessed through NIED, and the European data are accessed through Observatories and Research Facilities for European Seismology. We thank the extensive discussion with Hiroo Kanamori, Thorne Lay, Don Helmberger, Miyaki Ishii, Zach Ross, and Victor Tsai. We appreciate two anonymous reviewers for their constructive suggestions. This work is supported by National Basic Research Program of China grant 2012CB417301 and National Science Fundation of the United States grants 1447107 and ear1614609.

Attached Files

Published - grl55981.pdf

Supplemental Material - grl55981-sup-0001-2017GL073254_SI.docx

Supplemental Material - grl55981-sup-0002-2017GL073254_ms01.avi

Supplemental Material - grl55981-sup-0003-2017GL073254_ms02.avi

Supplemental Material - grl55981-sup-0004-2017GL073254_ms03.mov


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