Mapping the Upper Mantle Discontinuities beneath China with Teleseismic Receiver Functions
Shen, Xuzhang, Huilan Zhou, and Kawakatsu, H.,
Earth Planets Space , , in press, 2008.
(preprint PDF)
We use teleseismic body waves recorded at stations of the Chinese Center of
Digital Seismic Network to map the upper mantle discontinuities beneath China.
Referring to the CRUST2.0 and a S-tomography model beneath each station,
the 1-D ray tracing method is used to convert time series of radial receiver functions
to depth series. Clear signatures corresponding to the 410- and 660-km
discontinuities (¡Æ410¡Ç and ¡Æ660¡Ç) are visible at almost all of the stations.
The average S velocity contrast of ¡Æ410¡Ç beneath the study area is close to
the global average, but for ¡Æ660¡Ç, the S velocity contrast is smaller than the
global average. The average depth of ¡Æ410¡Ç is 413 km, and the peak-to-peak
topography is about 36 km, with regional depressions that correlate with
the Datong quaternary volcano in north China. The ¡Æ660¡Ç topography
exhibits peak-to-peak variation of about 43 km, and its average depth is 669 km;
the depressions of the ¡Æ660¡Ç in northeastern, southeastern and northern China are
well correlated with the past subduction around the Pacific Ocean and Philippine Sea.
The width of the transition zone is also increased in the region with the deeper ¡Æ660¡Ç.
Our results seem to indicate that there may be a low velocity layer below ~600 km,
which may be the accumulated garnetite layer of ancient crust above the ¡Æ660¡Ç.