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The low-velocity layer at the depth of 620 km beneath Northeast china

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chinese Science Bulletin 2009年第17期54卷 3067-3075页

作者： shen xuzhang zhou huilan laboratory of computational geodynamics Graduate University of the Chinese Academy of Sciences Beijing 100049 China Lanzhou Institute of Seismology China Earthquake Administration Lanzhou 730000 China

Based on the 3-D Earth model, the common convert points-phase weighted stacks (CCP-PWS) migra- tion method is used to image the upper mantle discontinuities beneath Northeast china (longitude 120°―132°; latitude 38°―40°) with 802 observed receiver functions. Teleseismic records are obtained from 4 stations belonging to CCDSN and 19 stations belonging to PASSCAL. A low-velocity layer has been detected at the depth of 620 km. This low-velocity layer rises to 600 km in the east of the study region close to the subducted slab. We consider that this low-velocity layer might be the accumulated oceanic crustal material delaminated from the western Pacific subducted slab. Additionally, we detect the obvious depression of 660 km discontinuity which was attributed to the interaction between the upper mantle and subducted slab. The maximum depth of 660 km discontinuity approaches 700 km, and 660 km discontinuity splits into multiple discontinuities in the northeast of the study region.

关键词：中国东北低速层公里 PASSCAL 地幔间断面地球模型迁移方法物质积累

Receiver functions of CCDSN and crustal structure of chinese mainland

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Earthquake Science 2012年第1期25卷 3-16页

作者： xuzhang shen huilan zhou Lanzhou Institute of Seismology China Earthquake AdministrationLanzhou 730000China laboratory of computational geodynamics Graduate University of Chinese Academy of SciencesBeijing 100049China

The teleseismic receiver functions of 48 stations belonging to the CCDSN are used to invert the crustal structure beneath each station with the neighborhood algorithm. Thin layers with low velocity have been found beneath eight stations with ＂abnormal＂ observed receiver functions. Unreasonable results of few stations have been adjusted lightly with the trial-and-error method. The final result indicates that the crust in the western china is relatively thicker than the eastern china. The crust thickness beneath the Tibetan plateau is very large, which reaches 84 km at the station LSA. Double-crust structure exists below the stations LSA and CAD in Tibet, which might imply the collision between the Indian and Eurasian plates. A pronounced low velocity zone in the lower crust beneath the station TNC of Yunnan province might relate to the high temperature or emergence of partially molten material caused by Quaternary volcano, magma and geothermal activities in this area. The Moho is a transitional zone made up of thin layers instead of simple sharp discontinuity beneath several stations. The Conrad discontinuity is clearly identified beneath 20 stations mainly in the southeastern china, whereas it is blurry beneath 14 stations and uncertain beneath remaining stations.

关键词： receiver function neighborhood algorithm chinese mainland crust structure

Peeling linear inversion of upper mantle velocity structure with receiver functions

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Earthquake Science 2012年第1期25卷 65-74页

A peeling linear inversion method is presented to study the upper mantle （from Moho to 800 km depth） velocity structures with receiver functions. The influences of the crustal and upper mantle velocity ratio error on the inversion results are analyzed, and three valid measures are taken for its reduction. This method is tested with the IASP91 and the PREM models, and the upper mantle structures beneath the stations GTA, LZH, and AXX in northwestern china are then inverted. The results indicate that this inversion method is feasible to quantify upper mantle discontinuities, besides the discontinuities between 3hM （hM denotes the depth of Moho） and 5hM due to the interference of multiples from Moho. Smoothing is used to overcome possible false discontinuities from the multiples and ensure the stability of the inversion results, but the detailed information on the depth range between 3hM and 5hM is sacrificed.

关键词： upper mantle receiver function peeling linear inversion