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Fine Structure of the 660‐km Discontinuity Beneath Southeastern China
Author(s) -
Zhang Meng,
Sun Daoyuan,
Wang Yi,
Wu Zhongqing
Publication year - 2019
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 - 10.1029/2019gl082639
Subject(s) - discontinuity (linguistics) , geology , transition zone , mantle (geology) , slab , plume , seismology , mantle plume , classification of discontinuities , geophysics , tectonics , lithosphere , meteorology , geography , mathematical analysis , mathematics
Imaging the structure of the 660‐km discontinuity is crucial to understanding the thermal and compositional states of the mantle transition zone. Here we study triplication data sampling beneath southeastern China and observe strong arrivals with rays turning at top of the lower mantle at an epicentral distance of 10°. Such strong arrivals indicate that the S velocity at the discontinuity increases by ~8.2±0.5% over less than 10 km. This sharp 660‐km discontinuity suggests that harzburgite enrichment exists at the bottom of the 660‐km discontinuity and the temperature near 660 km does not exceed 2000 K. Through comparisons with 1‐D models for other regions, we find that the seismic structure in the mantle transition zone below our study area is similar to that beneath oceanic regions. Thus, we suggest that the mantle near the 660‐km discontinuity beneath southeastern China is locally not affected by slab or plume.