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S-wave velocity and Poisson's ratio structure of crust in Yunnan and its implication

Science china Earth sciences 2005年第2期48卷 210-218页

作者： HU Jiafu, SU Youjin, zhu Xiongguan & CHEN Yun Geophysical Department of Yunnan University, Kunming 650091, china {2. Bureau of Yunnan Province, Kunming 650041, china institute of geology and Geophysics, chinese academy of sciences, beijing 100101, china 1. Geophysical Department of Yunnan University 650091 Kunming China 2. seismological Bureau of Yunnan Province 650041 Kunming China 3. institute of geology and Geophysics Chinese Academy of Sciences 100101 Beijing China

Receiver function of body wave under the 2. stations in Yunnan was extracted from 3-component broadband digital recording of teleseismic event. Thus, the S-wave velocity structure and distribution characteristics of Poisson's ratio in crust of Yunnan are obtained by inversion. The results show that the crustal thickness is gradually thinned from north to south. The crustal thickness in Zhongdian of northwest reaches as many as 62.0 km and the one in Jinghong of further south end is only 30.2.km. What should be especially noted is that there exists a Moho upheaval running in NS in the Chuxiong region and a Moho concave is generally parallel to it in Dongchuan. In addition, there exists an obvious transversal inhomogeneity for the S-wave velocity structure in upper mantle and crust in the Yunnan region. The low velocity layer exists not only in 10.0-15.0 km in upper crust in some regions, but also in 30.0-40.0 km in lower crust. Generally, the Poisson's ratio is on the high side, however it has a better corresponding relation to the crustal velocity structure. An obvious block distribution feature is still shown on such a high background of Poisson's ratio. It is discovered by synthetically analyzing the velocity structure and Poisson's ratio distribution that there are high Poisson's ratio and complicated crust-mantle velocity structure feature in the Sichuan-Yunnan Diamond Block with Xiaojiang fault to be the east boundary and Yulong Snow Mountain fault to be the west boundary besides the frequent seismicity. This feature differs obviously from that of surrounding areas, which would provide geophysical evidence to deeply study the eastwardly flowage of lithospheric substances in the Qinghai-Tibet Plateau.

关键词： Yunnan, S-wave velocity, Poisson's ratio, Sichuan-Yunnan Diamond Block.

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New evidence from seismic imaging for subduction during assembly of the North china craton:REPLY

New evidence from seismic imaging for subduction during asse...

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中国科学院地质与地球物理研究所第十届(2.10年度)学术年会

作者： tianyu zheng~**,liang zhao,{2.(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing 10002.,china

As mentioned in the Comment from zhao et al.(2.10),our original paper(zheng et al.,2.09) provides the first images of the crustal structure beneath the Western block and across its boundary with the Trans-North {2. ...

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Moment tensor analysis of the acoustic emission source in the rock damage process

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Progress in Natural Science:Materials International 2005年第7期15卷 609-613页

作者： YU Huaizhong, zhu Qingyong, YIN Xiangchu and WANG Yucang ( State Key laboratory of Earthquake Dynamics, {2. of geology, china Earthquake Administration, beijing 10002., china State Key laboratory of Nonlinear Mechanics, {2. of Mechanics, chinese academy of sciences, beijing 100080, china School of Mathematics and Computational Science, Zhongshan University, Guangzhou 5102.5, china Center for Analysis and Prediction, china seismological Bureau, beijing 100036, china Quakes, Department of Earth Science, University of Queensland, Brishbane, Austrialia) State Key laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing 100029 China. State Key laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China. School of Mathematics and Computational Science Zhongshan University Guangzhou 510275 China. Center for Analysis and Prediction China Seismological Bureau Beijing 100036 China. Quakes Department of Earth Science University of Queensland Brishbane Austrialia

To further investigate the mechanism of acoustic emission (AE) in the rock fracture experiment, moment tensor analysis was carried out. The AE sources characterized by crack sizes, orientations and fracture modes, are represented by a time-dependent moment tensor. Since the waveforms recorded by AE monitors correlate to the moment tensors, we prefer to select the P wave amplitude from the full-space Green's function of homogeneous and isotropic materials to determine the six independent components of the moment tensor. The moment tensor analysis was used to investigate the AE sources recorded in the experiment, and three types of micro-cracks were found, which are tensile mode, shear mode and mixture of the tensile and shear mode. In addition, the motion of micro-cracks was decided by eigenvectors of moment tensor. Results indicate that the moment tensor analysis may be used as a measurement to reflect the damage evolution of rock specimen.

关键词： moment tensor acoustic emission rock fracture.

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Mantle dynamics of the reactivating North china Craton:Constraints from the topographies of the 410-km and 660-km discontinuities

Mantle dynamics of the reactivating North China Craton:Const...

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中国科学院地质与地球物理研究所第11届（2.11年度）学术年会

作者： XU WeiWei~*,zheng tianyu & {2. liang seismological laboratory,State Key laboratory of Lithospheric Evolution,institute of geology and Geophysics, chinese academy of sciences,beijing,10002.,{12.

The topographies of the 410-km and 660-km discontinuities have important implications for mantle *** we present high-resolution seismic imaging of the 410-km and 660-km discontinuities beneath the North china Craton(NCC) employing the receiver function *** anomalies(deeper or shallower than the global average depths) at both discontinuities were detected by introducing a three-dimensional regional velocity *** depressions of the 410-km discontinuity are mostly located in the eastern NCC.A local elevation of the 660-km discontinuity appeared in the northwest of the NCC and a significant depression of the 660-km discontinuity is located in the southeast of the *** dynamic mantle regimes are speculated to explain the formation of the anomalous depth zones in the *** possibility is a complex mantle upwelling linked to edge-derived convection between the stagnant slab and the thick cratonic *** other potential dynamic regime is slab stagnating,sinking,and induced upwelling at the neighboring slab *** regimes hint that the mantle flow was possibly dominated by dynamic interactions among the subducting slab,cratonic root,and ambient mantle beneath the NCC.

关键词： 410-km discontinuity 660-km discontinuity receiver function imaging dynamic mantle regime North china Craton

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Distinct lateral variation of lithospheric thickness in the Northeastern North china Craton

Distinct lateral variation of lithospheric thickness in the ...

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中国科学院地质与地球物理研究所2.08学术年会

作者： Ling Chen~*,Wang Tao,liang zhao,tianyu zheng~* {2. laboratory(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing 10002.,china

A detailed knowledge of the thickness of the lithosphere in the northeastern North china Craton(NCC) is important for understanding the significant tectonic reactivation of the craton in the Mesozoic and Cenozoic *** achieve this goal by applying the newly proposed wave equation-based migration technique to the S-receiver functions recently collected in the *** negative signals are identified below the Moho in all the S-receiver function-migrated images and stacks,which we interpret as representing the S-to-P conversions from the lithosphereasthenosphere boundary(LAB).The imaged LAB is as shallow as～60-70 km in the southeast basin and coastal areas and deepens to no more than 140 km in the northwest mountain ranges and continental *** observations indicate widespread lithospheric thinning in the study region in comparison with the>180-km lithospheric thicknesses typical of most cratonic *** revealed topography of the LAB generally agrees with the lateral variation in upper mantle seismic anisotropy previously measured through SKS splitting *** particular,a sharp LAB step of～40 km is detected at the triple junction of the basin and mountains,at almost the same place where an abrupt change from NW-SE to NE-SW in fast polarization direction of shear waves was *** findings suggest a close correlation between the seismic anisotropy and hence deformation of the upper mantle,the lithospheric thickness,and the surface tectonics of the northeastern *** the thinned lithosphere and the NW-SE fast shear wave polarizations in the east areas probably are related to the dominant NW-SE tectonic extension in the late Mesozoic-Cenozoic time,the thicker lithosphere and the NE-SW fast polarization direction in the west mountain ranges may reflect earlier contractional deformations of the *** tests indicate that the LAB beneath the northeastern NCC is a well-defined zone 10-2. km *** with seismic tomography

关键词： lithosphere-asthenosphere boundary northeastern North china Craton S-receiver functions lithospheric reactivation

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Destruction geodynamics of the North china Craton and its Paleoproterozoic plate tectonics

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chinese Science Bulletin 2009年第19期54卷 3354-3366页

作者： zhu rixiang {2. tianyu Paleomagnetism and Geochronology laboratory (SKL-LE) Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

Much attention has been paid in the last two decades to the physical and chemical processes as well as temporal-spatial variations of the lithospheric mantle beneath the North china Craton. In order to provide insights into the geodynamics of this variation, it is necessary to thoroughly study the state and structure of the lithospheric crust and mantle of the North china Craton and its adjacent regions as an integrated unit. Based on the velocity structure of the crust and upper mantle constrained from {2. studies, this paper presents various available geophysical results regarding the lithosphere thickness, the nature of crust-mantle boundary, the upper mantle structure and deformation characteristics as well as their tectonic features and evolution systematics. Combined with the obtained data from petrology and geochemistry, a mantle flow model is proposed for the tectonic evolution of the North china Craton during the Mesozoic-Cenozoic. We suggest that subduction of the Pacific plate made the mantle underneath the eastern Asian continent unstable and able to flow faster. Such a regional mantle flow system would cause an elevation of melt/fluid content in the upper mantle of the North china Craton and the lithospheric softening, which, subsequently resulted in destruction of the North china Craton in different ways of delamination and thermal erosion in Yanshan, Taihang Mountains and the Tan-Lu Fault zone. Multiple lines of evidence recorded in the crust of the North china Craton, such as the amalgamation of the Archean eastern and western blocks, the subduction of Paleo-oceanic crust and Paleo-continental residue, indicate that the Earth in the Paleoproterozoic had already evolved into the plate tectonic system similar to the present plate tectonics.

关键词：地球动力学筑造学研究调查

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A thinned lithospheric image of the Tanlu Fault Zone,eastern china:Constructed from wave equation based receiver function migration

A thinned lithospheric image of the Tanlu Fault Zone,eastern...

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中国科学院地质与地球物理研究所2.06学术年会

作者： Ling Chen,tianyu zheng~*,and Weiwei Xu seismological {2.(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing 10002.,PR china

We apply the newly proposed wave equation-based receiver function poststack migration method to the Northern china interior Structure Project broadband data to image the lithospheric structure of the Tanlu Fault Zone area in eastern *** migration result reveals a 60- to 80-km-thick present-day lithosphere beneath the study region,significantly thinned from the Paleozoic lithosphere of >180 *** lithosphere asthenosphere boundary(LAB) is coherently imaged along the 00-km east-west profile,displaying an arc-like shape with its apex roughly coincident with the transverse location of the Tanlu Fault Zone on the *** obvious uplift from6 km to2.km of the Moho is also clearly detected right below this fault *** coincidence of the imaged Moho uplift and the LAB apex with the surface location of the Tanlu Fault Zone provides seismological evidence for the steep geometry and deep penetration of the fault system,and indicates that the Tanlu Fault Zone might have acted as a major channel for anthenosphere upwelling during the Mesozoic-Cenozoic continental extension and lithospheric thinning in eastern *** analysis and synthetic modeling suggest that both the Moho and the LAB are sharp and *** latter,in particular,is constrained to have a 3-7%drop in S wave velocity over a depth range of 10 km or *** a rapid velocity change at the base of the lithosphere in the study region cannot be solely explained by thermal variation,but likely reflects the presence of volatiles or melt in the asthenosphere,or is partially attributed to the compositional contrast between the preserved depleted and dehydrated cratonic lithospheric veneer and the uplifted hydrated and fertile asthenospheric materials.

关键词： Tanlu Fault Zone Receiver function Migration Lithosphere thinning

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Receiver function migration image of the deep structure in the Bohai Bay Basin,eastern china

Receiver function migration image of the deep structure in t...

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中国科学院地质与地球物理研究所2.06学术年会

作者： Ling Chen~*,tianyu zheng~*,and Weiwei Xu seismological {2.(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing 10002.,PR china

We apply a receiver function poststack migration method to image the crustal and upper mantle structures beneath the Bohai Bay Basin,eastern *** thick sediments of the basin appear to have a substantial influence on the migrated image of the deep *** using the surface reflected PpPs multiples instead of the commonly used Ps converted phases,a curved Moho is coherently imaged,showing a thinned crust of 30 km in the basin area compared with the >40-km thick crust in the west mountain *** incorporating the sedimentary velocity model into migration,both the 410-km and the 660-km discontinuities present a simple structural feature with relatively flat topography within the basin’s interior,although possible local structural complexities may exist at the base of the upper mantle around the boundary areas of the *** mantle transition zone is on average 10-15 km thicker than the global average,reflecting a cold lower upper mantle environment that is distinct from the warm shallow upper mantle of the region.

关键词： Bohai Bay Basin Receiver function Migration Mantle transition zone Sediment influence

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Insight into craton evolution:Constraints from shear wave splitting in the North china Craton

Insight into craton evolution:Constraints from shear wave sp...

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中国科学院地质与地球物理研究所2.08学术年会

作者： liang zhao~*,tianyu zheng~*,Gang L(u|¨) {2. laboratory(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing 10002.,china

The multi-episodic tectonic activities from the Precambrian to Cenozoic,including nucleus formation, cratonic amalgamation,and rejuvenation,make the North china Craton(NCC) an ideal natural laboratory for studying craton *** change in the upper deformation records is an important aspect for understanding cratonic formation and *** this study,we performed seismic shear wave splitting analysis using SKS phases from 50 portable *** different methodologies,shear wave splitting measurement and amplitude analysis of transverse/radial components,produced mutually consistent splitting *** results showed that the seismic anisotropy beneath the Ordos Block can be divided into three subgroups reflecting the tectonic *** these results with those from previous splitting studies in the eastern NCC,we suggest that the Proterozoic amalgamation generated the seismic anisotropy in the boundary zone between the Ordos Block and the Trans-North china Orogen, while the anisotropy in the eastern Trans-North china Orogen and eastern NCC were possibly associated with the lithospheric rejuvenation during the Late Mesozoic to Cenozoic.

关键词： North china Craton Upper mantle Seismic anisotropy Shear wave splitting

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Insight into the geodynamics of cratonic reactivation from seismic analysis of the crust-mantle boundary

Insight into the geodynamics of cratonic reactivation from s...

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中国科学院地质与地球物理研究所2.08学术年会

作者： T.Y.zheng,L.zhao,and R.X.{2. 1 seismological laboratory(SKL-LE),institute of geology and Geophysics,chinese academy of sciences,beijing,china.

[1]The reactivation of craton is a crucial issue for the understanding of continent *** the partial loss of the thick lithospheric root of the North china Craton (NCC) was documented,its mechanism remains a contentious topic in the study of cratonic *** this paper,we imaged the crust-mantle structures by using the data from 36 permanent stations with fine spatial coverage in the Yanshan tectonic belt(YSTB) and the Taihangshan region(TSR) in the northern *** tectonic units with distinct crust-mantle structures were recognized and their junction zone was *** results reveal distinct features of the crust-mantle boundaries of the YSTB and the TSR which are characterized by a sharp interface and a thick transition zone,*** on the analysis of the seismic structures of the crust-mantle boundary and the upper mantle,we propose that the NCC reactivation was possibly derived by a slow secular ascension of hydrated asthenospheric material atop the stagnant Pacific slab,which influenced the formation of crust-mantle transition zone in the eastern *** the other hand, regional delamination of the deep crust after orogenic thickened and/or magmatic underplating beneath the YSTB caused the spatial variation of the crust-mantle boundary. Both of the mantle processes possibly changed the nature of the lithospheric mantle.

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