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A fast velocity anomaly to the west of the Australian‐Antarctic discordance
Author(s) -
Kuo BanYuan,
Chen ChauHuei,
Zhang YuShen
Publication year - 1996
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 - 10.1029/96gl02144
Subject(s) - geology , geodesy , seismology , ridge , anomaly (physics) , rayleigh wave , geophysics , surface wave , physics , paleontology , optics , condensed matter physics
To examine the hypothesis that the Australian‐Antarctic Discordance overlays an anomalously cold upper mantle, we have measured Rayleigh wave group velocities along paths between the Southeast Indian Ridge and the Australian station NWAO. The group velocity peaks for events in the vicinity of 117°E, rather than for those within the discordance zone between 120 and 127°E. This variation is resolved at least for periods of 35–45 s. To model the cause, assumed velocity anomalies with simple geometry were tested using the surface wave Gaussian beam method in a forward sense. The preferred model consists of an elongated structure centered 300–500 km west of the discordance and stretching northward for at least 1000 km. The position of the anomalous structure is consistent with recent global tomographic models in this region.