云南及周边地区Lg尾波Q值的分布特征
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摘要
收集了昆明台 1990～ 2 0 0 0年间大于 4 .0级的地震宽频记录资料 ,以及分布在云南境内的 2 3个昆明数字化台网 1999～ 2 0 0 0年的资料 ,使用单台叠加谱比方法处理了 2 80个Lg尾波信号 .在假定Lg尾波Q与频率f有Q=Q0 fη关系的基础上 ,计算出各射线 1Hz时的Q值及频率相关因子 η .在此基础上 ,运用反投影技术反演得到云南及周边地区 0 .5°× 0 .5°网格内的Q0 和 η的分布图像 .结果表明 :云南及周边地区的Q0 在 15 0～ 30 0之间变化 ,滇东地区的Q0 明显高于滇西地区 ;η的变化范围在 0 .3～ 0 .8之间 ,绝大部分地区 η的变化范围为 0 .5～ 0 .6 .
We have collected broadband seismograms of earthquakes with magnitudes greater than 4.0 recorded by the Kunming station during the period 1990～2000 and 23 Kunming digital network stations located in Yunnan province during the period 1999～2000. The total 280 Lg coda traces are studied using the stack spectral ratio (SSR) method. Supposing Q of Lg coda correlates with frequency, f by Q=Q 0f η, the Q value at 1Hz, Q 0 and η for each record are calculated. Based on the calculated results, the distribution maps of Q 0 and η for 0.5°×0.5° cells are obtained using the back-projection technique. The results indicate Q 0 in Yunnan and its adjacent regions exhibits low values, varying between 150 and 300. Q 0 in eastern Yunnan is higher than that in western Yunnan. η varies between 0.3 and 0.8. For most of the study regions η is within the range between 0.5 and 0.6.
We have collected broadband seismograms of earthquakes with magnitudes greater than 4.0 recorded by the Kunming station during the period 1990～2000 and 23 Kunming digital network stations located in Yunnan province during the period 1999～2000. The total 280 Lg coda traces are studied using the stack spectral ratio (SSR) method. Supposing Q of Lg coda correlates with frequency, f by Q=Q 0f η, the Q value at 1Hz, Q 0 and η for each record are calculated. Based on the calculated results, the distribution maps of Q 0 and η for 0.5°×0.5° cells are obtained using the back-projection technique. The results indicate Q 0 in Yunnan and its adjacent regions exhibits low values, varying between 150 and 300. Q 0 in eastern Yunnan is higher than that in western Yunnan. η varies between 0.3 and 0.8. For most of the study regions η is within the range between 0.5 and 0.6.
引文
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[20] 熊绍柏,郑 晔,尹周勋等.丽江—攀枝花—者海地带二维地壳结构及其构造意义.地球物理学报,1993,36(4):288～301XIONGShaobai,ZHENGYe,YINZhouxun,etal.The2Dstruc tureanditstectonicimplicationofthecrustintheLijiang—Panzhi hua—Zhehairegion.ChineseJ.Geophys.(ActaGeophysicaSinica),1993,36(4):288～301
[2] HerrmannRB ,KijkoA .ModelingsomeempiricalLgrelations.Bull.Seism.Soc.Am.,1983,56:172～257
[3] WangCY ,HerrmannRB .Synthesisofcodawavesinlayeredmedi um.PureAppl.Geophys.,1988,128:7～42
[4] ZhangT ,LayT .WhytheLgphasedoesnottraverseoceaniccrust.Bull.Seism.Soc.Am.,1995,85:1665～1678
[5] MitchellBJ.Anelasticstructureandevolutionofthecontinentalcrustanduppermantlefromseismicsurfacewaveattenuation.Rev.ofGeo physics,1995,33(2):441～462
[6] HerrmannRB .Qestimatesusingcodaoflocalearthquakes.Bull.Seism.Soc.Am.,1980,70:447～469
[7] XieJ ,NuttliOW .Interpretationofhigh frequencycodaatlargedis tances:stochasticmodelingandmethodofinversion.GeophysicalJ .Int.,1988,95:579～5951
[8] AkiK .Analysisoftheseismiccodaoflocalearthquakesasscattedwaves.J.Geophys.Res.,1969,74(2):615～663
[9] BaqerS ,MitchellBJ .RegionalvariationsofLgcodaQintheconti nentalUnitedStatesanditsrelationtocrustalstructureandevolution.PureAppl.Geophys.,1998,158:613～638
[10] DeSouzaJL ,MitchellBJ.LgcodaQvariationsacrossSouthAmeri caandtheirrelationtocrustalevolution.PureAppl.Geophys.,1998,158:587～612
[11] CongL ,MitchellBJ.LgcodaQanditsrelationtothegeologyandtectonicsoftheMiddleEast.PureAppl.Geophys.,1998,158:563～585
[12] MitchellBJ ,BaqerS ,AkinciA ,etal.LgcodaQinAustraliaanditsrelationtocrustalstructureandevolution.PureAppl.Geophys.,1998,158:639～653
[13] MitchellBJ ,PanY ,XieJ ,etal.LgcodaQvariationacrossEurasiaanditsrelationtocrustalevolution.J.Geophys.Res.,1997,102:22767～22779
[14] XieJ,MitchellBJ.Aback projectionmethodforimaginglarge scalelateralvariationsofLgcodaQwithapplicationtocontientalAfrica.Geophys.J .Int.,1990,100(1):161～181
[15] NuttliOW .LgmagnitudesandyieldestimatesforundergroundNo vayaZemlyanuclearexplosions.Bull.Seism.Soc.Am.,1988,78:873～884
[16] 秦嘉政,阚荣举.用近震尾波估算昆明及周围地区的Q值和地震矩.地球物理学报,1986,29(2):145～155QINJiazheng,KANRongju.QvaluesandseismicmomentsestimatesusingthecodawavenearearthquakesintheKunmingandsurroundingregions.ChinesJ .Geophys.(ActaGeophysicaSinica),1986,29(2):145～155
[17] 汪辑安,徐 青,张文仁等.云南大地热流及地热地质问题.地震地质,1990,12(4):367～377WANGJi’an,XUQing,ZHANGWenren,etal.Heatflowdataandsomegeologic geothermalproblemsinYunnanprovince.SeismologyandGeology,1990,12(4):367～377
[18] 孙 洁,徐常芳,江 剑等.滇西地区地壳上地幔电性结构与地壳构造运动的关系.地震地质,1989,11(1):1～11SUNJie,XUChangfang,JIANGJian,etal.Theelectronicconduc tivitystructureinthecrustanduppermantleinwesternYunnanregionandtherelationbetweenitandthecrusttectonicmovement.Seismolo gyandGeology,1989,11(1):1～11
[19] 陈培善,刘福田,李 强等.云南地区速度结构横向不均匀性.中国科学(B辑),1990,20(4):431～438CHENPeishan,LIUFutian,LIQiang,etal.Thelateralinhomoge neityofvelocitystructureinYunnanregion.ScienceinChina(SeriesB),1990,20(4):431～438
[20] 熊绍柏,郑 晔,尹周勋等.丽江—攀枝花—者海地带二维地壳结构及其构造意义.地球物理学报,1993,36(4):288～301XIONGShaobai,ZHENGYe,YINZhouxun,etal.The2Dstruc tureanditstectonicimplicationofthecrustintheLijiang—Panzhi hua—Zhehairegion.ChineseJ.Geophys.(ActaGeophysicaSinica),1993,36(4):288～301
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