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Topography of the 660‐km discontinuity beneath northeast China: Implications for a retrograde motion of the subducting Pacific slab
Author(s) -
Li Juan,
Chen QiFu,
Vanacore Elizabeth,
Niu Fenglin
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 - 10.1029/2007gl031658
Subject(s) - geology , seismology , slab , discontinuity (linguistics) , seismogram , pacific plate , subduction , tectonics , geophysics , mathematical analysis , mathematics
Clear S to P converted waves at the 660‐km discontinuity ( S 660 P ) are observed at stacked seismograms of deep earthquakes occurring in northeast China and Japan Sea recorded by broadband seismic arrays in North America and Europe. Differential travel times between the S 660 P and P waves are used to constrain depth variations of the 660 beneath northeast China. A rapid change in the depth of the 660 is observed within a narrow longitudinal range of 130.8°E–131.4°E, where the lower boundary of the subducting slab encounters the 660. Towards the west, the 660 deepens steadily as it approaches the coldest core of the slab. The maximum depression occurs at the west end of the studied region with an amplitude of ∼20 km. To the east, the 660 appears to be flat, showing no obvious effect of the subducting slab. These observations are consistent with a scenario for a retrograde moving Pacific slab lying over the upper and lower mantle boundary progressively from west to east.