Mantle Anisotropy beneath China: Measurements and Implications
Seismic anisotropy in the mantle beneath mainland China was studied using data from the China Digital Seismograph Network (CDSN) by Zheng & Gao (1994), and later by using data from more stations and different seismograph networks. The present study utilizes data from the recently-completed China National Seismograph Network (CNSN) from 2001 to 2005 to further improve the coverage of anisotropy measurements, and to search for the existence of complex anisotropy beneath stations with sufficient azimuthal coverage of the events. China is an ideal locale for studying the formation of mantle anisotropy by various mechanisms, such as continental collision along the Himalayas, slab-subducting beneath its eastern region, and continental splitting in the vicinity of the Shanxi and other rifts. Using data recorded over the past five years by the 48 stations in CNSN, this study obtains seismic anisotropic parameters (fast polarization directions and time delays) of split shear-waves. In addition, we use hundreds of events recorded by stations in the Global Seismograph Network (GSN) to detect and analyze complex anisotropy. Our results can be well-explained by coherent deformation of the lithosphere in the past or current orogenic belt, or by asthenospheric flow induced by subducting oceanic slabs. The measurements suggest that the western limit of the approximately westward asthenospheric flow induced by the subducting Pacific slab is consistent with the western boundary of the recent sedimentary basins in eastern China, suggesting that there is a possible connection between the formation of the large sedimentary basins and the slab, which is deflected horizontally in the mantle transition zone, as revealed by recent seismic tomographic studies. This study is supported by NSFC.
Y. Gao et al., "Mantle Anisotropy beneath China: Measurements and Implications,", vol. 87, no. 52 American Geophysical Union (AGU), Dec 2006.
AGU Fall Meeting (2006: Dec. 11-15, San Francisco, CA)
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Seismology; Body Waves; Mantle
Article - Conference proceedings
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