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Pn anisotropic tomography and dynamics under eastern Tibetan plateau
Author(s) -
Lei Jianshe,
Li Yuan,
Xie Furen,
Teng Jiwen,
Zhang Guangwei,
Sun Changqing,
Zha Xiaohui
Publication year - 2014
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2013jb010847
Subject(s) - geology , subduction , mantle (geology) , seismology , lithosphere , seismic anisotropy , plateau (mathematics) , transition zone , seismic tomography , upwelling , slab , tectonics , structural basin , paleontology , geophysics , mathematical analysis , mathematics , oceanography
Abstract We present a new anisotropic tomographic model of the uppermost mantle around eastern Tibet using Pn traveltime data from a newly deployed temporary seismic array and recent observation bulletins of Chinese provincial networks. Our results are generally consistent with previous results but provide new insights into the dynamics of Tibetan plateau. Prominent high‐velocity (high‐V) anomalies are visible under Alashan block and Qaidam and Sichuan basins, which clearly outline their tectonic margins. A distinct high‐V zone representing the double‐sided subduction of Indo‐Eurasian plates is imaged from Lhasa block to the south of Qaidam basin. A pronounced low‐velocity (low‐V) zone is observed from Songpan‐Ganzi block to southern Chuan‐Dian diamond block, suggesting the existence of hot material upwelling there. Crustal strong earthquakes frequently occurred around high‐V anomalies or transition zones from high‐V to low‐V anomalies, suggesting that these earthquakes could be related to lateral heterogeneities in the mantle. The Pn fast direction approximately rotates around Eastern Himalayan Syntaxis, and it is tangential to the margins of Sichuan basin, suggesting that the mantle material flow of Tibetan plateau may have affected east China. In the Yunnan region to the south of 26°N, the Pn fast direction is different from SKS splitting results, indicating that the mantle lithosphere could be mechanically decoupled at certain depth below the uppermost mantle, which might be attributable to the subduction of Indian (or Burma) slab. Although the correlation between anisotropy and velocity is complicated, anisotropy strength could be associated with the pattern of velocity anomalies in the region.