云南地区SKS波分裂研究
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摘要
根据云南数字地震台网和云南流动地震台网的台站,以及中国国家数字地震台网(CNDSN)腾冲台和昆明台,共计47个台站记录到的远震SKS波震相,计算了各个台站下方的各向异性,讨论并分析了各向异性层的深度、厚度、起因,进一步探讨了与青藏高原东南缘地区地球动力学有关的一些问题.从得到的结果来看,云南北部的各向异性的快波偏振方向呈南北向,逐渐过渡到南部的近东西向,整体来看,有一旋转的趋势.分析表明各向异性层主要分布于上地幔,时间延迟在0·58~1·88s,厚度在67~216km之间.青藏高原存在垂直向隆升变形和东西向拉张变形外,地幔物质还向东南运移.
SKS shear waves recorded at 47 stations, which are located in Yunnan and involve Yunnan digital seismograph network, Yunnan temporary seismometer arrays, and China National Digital Seismograph Network (CNDSN), are used to analyze the direction and extent of seismic anisotropy. Furthermore, some problems related to the dynamics of the Qinghai_Tibetan plateau are discussed. It is demonstrated that delay times vary from 0.58 to 1.88s and fast wave polarization directions are present at stations with nearly N-S in northern Yunnan and gradually rotate to W-E in southern Yunnan. The shear wave splitting is mainly due to the anisotropy in the upper mantle whose thickness is between 67km and 216km. It is possible that the collision of the India and Eurasia plates resulted in not only crustal thickening and subsequently the E-W extension beneath the Qinghai_Tibetan plateau, but also mantle material flow southeastward.
SKS shear waves recorded at 47 stations, which are located in Yunnan and involve Yunnan digital seismograph network, Yunnan temporary seismometer arrays, and China National Digital Seismograph Network (CNDSN), are used to analyze the direction and extent of seismic anisotropy. Furthermore, some problems related to the dynamics of the Qinghai_Tibetan plateau are discussed. It is demonstrated that delay times vary from 0.58 to 1.88s and fast wave polarization directions are present at stations with nearly N-S in northern Yunnan and gradually rotate to W-E in southern Yunnan. The shear wave splitting is mainly due to the anisotropy in the upper mantle whose thickness is between 67km and 216km. It is possible that the collision of the India and Eurasia plates resulted in not only crustal thickening and subsequently the E-W extension beneath the Qinghai_Tibetan plateau, but also mantle material flow southeastward.
引文
[1]Hiramasu Y,Ando M,Ishikawa Y.ScS wave splitting of deep earthquakes around Japan.Geophys.J.Int.,1997,128:409~424
[2]Hess HH.Seismic anisotropy of the uppermost mantle under ocean.Nature,1964,203:629~631
[3]Nicolas A,Christensen NI.Formation of anisotropyin upper mantle peridotites:Areview,in composition structure and dynamics of the lithosphere-asthenosphere system.Geodyn.Ser.,1987,16:111~123
[4]Montagner J P,Tanimoto T.Global anisotropy in the upper inferred fromthe regionalizationof phase velocities.J.Geophys.Res.1990,95:4797~4819
[5]Ando M,Ishikawa Y.Observations of the shear-wave velocity polarization anisotropy beneath Honshu,Japan:Two masses with different polarizations inthe upper mantle.J.Phys.Earth,1982,30:191~199
[6]Vinnik L P,Kosarev G L,Makeyeva L I.Anisotropy in the lithosphere fromthe observations of SKS and SKKS.Dok.Acad.,Nauk SSSR(in Russian),1984,278:1335~1339
[7]Silver P G,Chan W W.Implication for continental structure and evolutionfromseismic anisotropy.Nature,1988,35:34~39
[8]Silver P G,Chan W W.Shear wave splitting and subcontinental mantle deformation.J.Geophys.Res.,1991,96:16429~16454
[9]郑斯华,高原.中国大陆岩石层的方位各向异性.地震学报,1994,16(2):131~140Zheng S H,Gao Y.Azimuth anisotropy of lithosphere of continental China.Acta Seismologica Sinica(in Chinese),1994,16(2):131~140
[10]丁志峰,曾融生.青藏高原横波分裂的观测研究.地球物理学报,1996,39(2):211~219Ding Z F.Zeng RS.Observation and study of shear wave anisotropy in Tibetan Plateau.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1996,39(2):211~219
[11]姜枚,许志琴,HirmA等.青藏高原及其部分邻区地震各向异性和上地幔特征.地球学报,2001,22(2):111~116Jiang M,Xu Z Q,Hirm A,et al.Eleseimic anisotropy and corresponding features of upper mantle in Tibetan Plateau and its neighboring areas.Acta Geoscientia Sinica(in Chinese),2001,22(2):111~116
[12]李白基.昆明地区上地幔地震方位异性.见:中国固体地球物理学进展.北京:海洋出版社,1994·330~338Li BJ.Seismic anisotropy of upper mantle in Kunming region.In:Progressin Chinese Solid Geophysics(in Chinese).Beijing:Ocean Press,1994·330~338
[13]阮爱国,王椿镛.云南地区上地幔各向异性研究.地震学报,2002,24(3):260~274Ruan AG,Wang C Y.The upper mantle anisotropyin Yunnanarea,China.Acta Seismologica Sinica(in Chinese),2002,24(3):260~274
[14]罗艳,黄忠贤,彭艳菊等.中国大陆及邻区SKS波分裂研究.地球物理学报,2004,47(5):812~821Luo Y,Huang Z X,Peng YJ,et al.Astudy on SKS wave splitting beneath the China mainland and adjacent regions.Chinese J.Geophy.(in Chinese),2004,47(5):812~821
[15]何正勤,叶太兰,苏伟.云南地区地壳中上部横波速度结构研究.地球物理学报,2004,47(5):838~844He Z Q,Ye TL,Su W.S wave velocitystructure of the middle and upper crust in the Yunnan region.Chinese J.Geophys.(in Chinese),2004,47(5):838~844
[16]吴小平,黄雍,冒蔚等.云南地震的潮汐应力触发机制及相关天体位置图像.地球物理学报,2005,48(3):574~583Wu XP,Huang Y,Mao W,et al.Tidal stresstriggering mechanism of earthquakes in Yunnan and related patterns of celestial body positions.Chinese J.Geophys.(in Chinese),2005,48(3):574~583
[17]胡家富,朱雄关,夏静瑜等.利用面波和接收函数联合反演滇西地区壳幔速度结构.地球物理学报,2005,48(5):1069~1076Hu J F,Zhu X G,Xia J Y,et al.Using surface wave and receiver functionto jointly inverse the crust-mantle velocity structure in the west Yunnan area.Chinese J.Geophys.(in Chinese),2005,48(5):1069~1076
[18]McNamara D E,Owens TJ,Silver PJ,et al.Shear wave anisotropy beneaththe Tibetan Plateau.J.Geophys.Res.,1994,99(B7):13655~13666
[19]刘希强,周蕙兰,李红等.中国大陆及邻区上地幔各向异性研究.地震学报,2001,23(4):337~348Liu X Q,Zhou HL,Li H,et al.Upper mantle anisotropy studyin China and adjacent regions.Acta Seismologica Sinica(in Chinese),2001,23(4):337~348
[20]Silver P G,Kaneshima,Meade C.Why is the lower mantle so isotropic?Eos Trans.AGU,1993,74:313
[21]Crampin S.A review of wave motion in anisotropic and cracked elastic-media.Wave Motion,1981,3:343~391
[22]许忠淮,汪素云,黄雨蕊等.由多个小震推断的青甘和川滇地区地壳应力场的方向特征.地球物理学报,1987,30(5):476~486Xu Z H,Wang S Y,Huang Y R,et al.Directions of mean stress axes in southwestern China deduced from microearthquake data.Chinese J.Geophys.(in Chinese),1987,30(5):476~486
[2]Hess HH.Seismic anisotropy of the uppermost mantle under ocean.Nature,1964,203:629~631
[3]Nicolas A,Christensen NI.Formation of anisotropyin upper mantle peridotites:Areview,in composition structure and dynamics of the lithosphere-asthenosphere system.Geodyn.Ser.,1987,16:111~123
[4]Montagner J P,Tanimoto T.Global anisotropy in the upper inferred fromthe regionalizationof phase velocities.J.Geophys.Res.1990,95:4797~4819
[5]Ando M,Ishikawa Y.Observations of the shear-wave velocity polarization anisotropy beneath Honshu,Japan:Two masses with different polarizations inthe upper mantle.J.Phys.Earth,1982,30:191~199
[6]Vinnik L P,Kosarev G L,Makeyeva L I.Anisotropy in the lithosphere fromthe observations of SKS and SKKS.Dok.Acad.,Nauk SSSR(in Russian),1984,278:1335~1339
[7]Silver P G,Chan W W.Implication for continental structure and evolutionfromseismic anisotropy.Nature,1988,35:34~39
[8]Silver P G,Chan W W.Shear wave splitting and subcontinental mantle deformation.J.Geophys.Res.,1991,96:16429~16454
[9]郑斯华,高原.中国大陆岩石层的方位各向异性.地震学报,1994,16(2):131~140Zheng S H,Gao Y.Azimuth anisotropy of lithosphere of continental China.Acta Seismologica Sinica(in Chinese),1994,16(2):131~140
[10]丁志峰,曾融生.青藏高原横波分裂的观测研究.地球物理学报,1996,39(2):211~219Ding Z F.Zeng RS.Observation and study of shear wave anisotropy in Tibetan Plateau.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1996,39(2):211~219
[11]姜枚,许志琴,HirmA等.青藏高原及其部分邻区地震各向异性和上地幔特征.地球学报,2001,22(2):111~116Jiang M,Xu Z Q,Hirm A,et al.Eleseimic anisotropy and corresponding features of upper mantle in Tibetan Plateau and its neighboring areas.Acta Geoscientia Sinica(in Chinese),2001,22(2):111~116
[12]李白基.昆明地区上地幔地震方位异性.见:中国固体地球物理学进展.北京:海洋出版社,1994·330~338Li BJ.Seismic anisotropy of upper mantle in Kunming region.In:Progressin Chinese Solid Geophysics(in Chinese).Beijing:Ocean Press,1994·330~338
[13]阮爱国,王椿镛.云南地区上地幔各向异性研究.地震学报,2002,24(3):260~274Ruan AG,Wang C Y.The upper mantle anisotropyin Yunnanarea,China.Acta Seismologica Sinica(in Chinese),2002,24(3):260~274
[14]罗艳,黄忠贤,彭艳菊等.中国大陆及邻区SKS波分裂研究.地球物理学报,2004,47(5):812~821Luo Y,Huang Z X,Peng YJ,et al.Astudy on SKS wave splitting beneath the China mainland and adjacent regions.Chinese J.Geophy.(in Chinese),2004,47(5):812~821
[15]何正勤,叶太兰,苏伟.云南地区地壳中上部横波速度结构研究.地球物理学报,2004,47(5):838~844He Z Q,Ye TL,Su W.S wave velocitystructure of the middle and upper crust in the Yunnan region.Chinese J.Geophys.(in Chinese),2004,47(5):838~844
[16]吴小平,黄雍,冒蔚等.云南地震的潮汐应力触发机制及相关天体位置图像.地球物理学报,2005,48(3):574~583Wu XP,Huang Y,Mao W,et al.Tidal stresstriggering mechanism of earthquakes in Yunnan and related patterns of celestial body positions.Chinese J.Geophys.(in Chinese),2005,48(3):574~583
[17]胡家富,朱雄关,夏静瑜等.利用面波和接收函数联合反演滇西地区壳幔速度结构.地球物理学报,2005,48(5):1069~1076Hu J F,Zhu X G,Xia J Y,et al.Using surface wave and receiver functionto jointly inverse the crust-mantle velocity structure in the west Yunnan area.Chinese J.Geophys.(in Chinese),2005,48(5):1069~1076
[18]McNamara D E,Owens TJ,Silver PJ,et al.Shear wave anisotropy beneaththe Tibetan Plateau.J.Geophys.Res.,1994,99(B7):13655~13666
[19]刘希强,周蕙兰,李红等.中国大陆及邻区上地幔各向异性研究.地震学报,2001,23(4):337~348Liu X Q,Zhou HL,Li H,et al.Upper mantle anisotropy studyin China and adjacent regions.Acta Seismologica Sinica(in Chinese),2001,23(4):337~348
[20]Silver P G,Kaneshima,Meade C.Why is the lower mantle so isotropic?Eos Trans.AGU,1993,74:313
[21]Crampin S.A review of wave motion in anisotropic and cracked elastic-media.Wave Motion,1981,3:343~391
[22]许忠淮,汪素云,黄雨蕊等.由多个小震推断的青甘和川滇地区地壳应力场的方向特征.地球物理学报,1987,30(5):476~486Xu Z H,Wang S Y,Huang Y R,et al.Directions of mean stress axes in southwestern China deduced from microearthquake data.Chinese J.Geophys.(in Chinese),1987,30(5):476~486