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1、documentclassarticleusepackagegraphicxusepackageroundnatbibbibliographystyleplainnatusepackagepdfstartview=FitH,%bookmarksnumbered=true,bookmarksopen=true,%colorlinks=true,pdfborder=001,citecolor=blue,%linkcolor=blue,urlcolor=bluehyperrefbegindocumenttitleResearch plan under the Post-doctorate progr

2、am at xx University%subtitleaaauthorRobert Hedate2008/04/23maketitlesectionResearch TitleCrustal seismic anisotropy in the xx using Moho P-to-S converted phases.sectionResearch Background & PurposesShear-wave splitting analyses provide us a new way to study the seismic structure andmantle dynamics i

3、n the crust and mantle. The crustal anisotropy is developed due to variousreasons including lattice-preferred orientation (LPO) of mineral crystals and oriented cracks.newlineTraditionally, the earthquakes occurring in the curst and the subducting plates are selected todetermine the seismic anisotro

4、py of the crust. However, none of these methods can help us toassess the anisotropy in the whole crust.Because crustal earthquakes mostly are located inthe upper crust, they do not provide information of lower crust. On the other hand, earthquakesin the subducting plates provide information of the w

5、hole crust but combined with uppermantle. However, its difficult to extract the sole contribution of the crust from themeasurement. Fortunately P-to-S converted waves (Ps) at the Moho are ideal for investigationof crustal seismic anisotropy since they are influenced only by the medium above the Moho

6、.Moho. Figure refcrustalsplitingschematically shows the effects of shear wave splitting onMoho Ps phases. Initially, a near-vertically incident P wave generates a radially polarizedconverted shear wave at the crust-mantle boundary. The phases, polarized into fast and slowdirections, progressively sp

7、lit in time as they propagate through the anisotropic media. Here,the Ps waves can be obtained from teleseismic receiver function analysis.%beginfigurehtbpbegincenterincludegraphicswidth=0.47textwidthcrustalsplit.pngcaptionThe effects of shear wave splitting in the Moho P to S converted phase. Top s

8、hows aschematic seismogram in the fast/slow coordinate system with split horizontal Pscomponents.(cited from: McNamara and Owens, 1993)labelcrustalsplitingendcenterendfigure%The Korean Peninsula is composed of three major Precambrian massifs, the Nangrim, Gyeongii,and Yeongnam massifs(Fig.refgeomap)

9、. The Pyeongbuk-Gaema Massif forms the southernpart of Liao-Gaema Massif of southern Manchuria, and the Gyeonggi and Mt. Sobaeksan massifsof the peninsula are correlated with the Shandong and Fujian Massifs of China.%beginfigurehtbpbegincenterincludegraphicswidth=0.755textwidthgeo.pngcaptionSimplifi

10、ed geologic map. NCB: North China block; SCB: South China block.(cited from:Choi et al., 2006)labelgeomapendcenterendfigure%Our purpose of the study is to measure the shear wave splitting parameters in the crust of theKorean Peninsula. The shear wave splitting parameters include the splitting time o

11、f shear energybetween the fast and slow directions, as well as fast-axis azimuthal direction in the KoreanPeninsula. These two parameters provide us constraints on the mechanism causing the crustalanisotropy. From the splitting time, the layer thickness of anisotropy will be estimated. Whethercrusta

12、l anisotropy mainly contributed by upper or lower crustal or both will be determined.Based on the fast-axis azimuthal direction, the tectonic relation between northeastern Chinaand the Korean peninsula will be discussed.sectionResearch MethodsSeveral methods have been introduced for calculation of r

13、eceiver functions. An iterativedeconvolution technique may be useful for this study since it produces more stable receiverfunction results than others. The foundation of the iterative deconvolution approach is aleast-squares minimization of the difference between the observed horizontal seismogram a

14、nda predicted signal generated by the convolution of an iteratively updated spike train with thevertical-component seismogram. First, the vertical component is cross-correlated with the radialcomponent to estimate the lag of the first and largest spike in the receiver function (the optimaltime is th

15、at of the largest peak in the absolute sense in the cross-correlation signal). Then theconvolution of the current estimate of the receiver function with the vertical-componentseismogram is subtracted from the radial-component seismogram, and the procedure isrepeated to estimate other spike lags and

16、amplitudes. With each additional spike in the receiverfunction, the misfit between the vertical and receiver-function convolution and the radialcomponent seismogram is reduced, and the iteration halts when the reduction in misfit withadditional spikes becomes insignificant.newlineFor all measurement

17、 methods of shear-wave splitting, time window of waveform should beselected. Conventionally the shear-wave analysis window is picked manually. However, manualwindow selection is laborious and also very subjective; in many cases different windows givevery different results.newlineIn our study, the au

18、tomated S-wave splitting technique will be used, which improves thequality of shear-wave splitting measurement and removes the subjectivity in window selection.First, the splitting analysis is performed for a range of window lengths. Then a cluster analysis isapplied in order to find the window rang

19、e in which the measurements are stable. Once clustersof stable results are found, the measurement with the lowest error in the cluster with thelowest variance is presented for the analysis result.sectionExpected results & their contributionsFirst, the teleseismic receiver functions(RFs) of all stati

20、ons including radial and transverseRFs can be gained. Based on the analysis of RFs, the crustal thickness can be estimated in theKorean Peninsula. Thenmost of the expected results are the shear-wave splitting parametersfrom RFs analysis in the crust beneath the Korean Peninsula. The thickness of ani

21、sotropic layerwill be estimated in the region when the observed anisotropy is assumed from a layer of lowercrustal material.All the results will help us to understand the crustal anisotropy source.newlineCrustal anisotropy can be interpreted as an indicator of the crustal stress/strain regime. Inadd

22、ition, since SKS splitting can offerthe anisotropy information contributed by the uppermantle but combined with the crust, the sole anisotropy of the upper mantle can be attractedfrom the measurement of SKS splitting based on the crustal splitting result.%citefrogge2007%citepfrogge2008%citeps-frogge

23、2007%5. Referencesbeginthebibliography99item Burdick, L. J. and C. A. Langston, 1977, Modeling crustal structure through the use ofconverted phases in teleseismic body waveforms, textitBull. Seismol. Soc. Am., 67:677-691.item Cho, H-M. et al., 2006, Crustal velocity structure across the southern Kor

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32、isotropy in the south-central Alborz regionusing Moho Ps converted phases, textitJ. Earth & Space Physics, 32(3):23-32.item Silver, P. G. and W. W. Chan, 1991, Shear wave splitting and subcontinental mantledeformation, textitJ. Geophys. Res.,96:16 429-16454.item Teanby, N. A. et al., 2004, Automatio

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34、st of the Korean peninsula byjoint inversion of surface-wave dispersion of teleseismic receiver functions, textitBull. Seismol.Soc. Am., 97(3):1 002-1 011.item Zhu, L., and H. Kanamori, 2000, Moho depth variation in Southern California fromteleseismic receiver functions, textitJ. Geophys. Res., doi :10.1029/1999JB900322, 105:2969-2 980.%enddocument