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Waveform effects of a metastable olivine tongue in subducting slabsVelocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to a depth of 670 km, as well as a plausible thermal anomaly; one model further included a 10-km-thick fast layer on the surface of the slab. The principal effect of MOTO is to produce grazing reflections at wide angles off the phase boundary, generating a secondary arrival 0 to 4 seconds after the initial arrival depending on the take-off angle. The amplitude and timing of this feature vary with the lateral location of the seismic source within the slab cross-section.
Document ID
19920036878
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Vidale, John E.
(USGS Menlo Park, CA, United States)
Williams, Quentin
(Geological Survey Menlo Park, CA, United States)
Houston, Heidi
(California, University Santa Cruz, United States)
Date Acquired
August 15, 2013
Publication Date
December 1, 1991
Publication Information
Publication: Geophysical Research Letters
Volume: 18
ISSN: 0094-8276
Subject Category
Geophysics
Accession Number
92A19502
Distribution Limits
Public
Copyright
Other

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