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Extent of the low‐velocity region in the lowermost mantle beneath the western Pacific detected by the Vietnamese Broadband Seismograph Array
Author(s) -
Takeuchi N.,
Morita Y.,
Xuyen N. D.,
Zung N. Q.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl033197
Subject(s) - geology , seismometer , seismology , broadband , vietnamese , mantle (geology) , geophysics , physics , optics , linguistics , philosophy
We present evidence showing the extent of the low‐velocity region in the lowermost mantle beneath the western Pacific. We analyzed S , sS , ScS ‐ S , and sScS ‐ sS travel times observed by the Vietnamese broadband seismograph array deployed as part of the Ocean Hemisphere Project. The abrupt changes in ScS ‐ S and sScS ‐ sS travel times suggest that the western geographical boundary of the low‐velocity region is located around 140°E and is sharp (more than 4% velocity contrast within 200 km). The dependency of S and sS travel time anomalies of epicentral distances suggests that the strong low‐velocity region is confined to within 400 km from the CMB (core‐mantle boundary). The existence of lateral heterogeneities with a 100 km scale inside the low‐velocity region is also suggested by the abrupt changes in S and ScS waveforms.