青藏高原东北缘—鄂尔多斯地壳上地幔地震层析成像研究
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摘要
根据横跨青藏高原东北缘—鄂尔多斯地区的流动宽频带地震台阵和区域地震台网的走时数据 ,利用地震层析成像方法研究了该地区 4 0 0km深度范围内地壳上地幔的P波速度结构 .结果表明 :青藏高原东北缘—鄂尔多斯地区地壳上地幔结构呈明显的横向不均匀性 .这种不均匀性体现在不同块体之间 ,同时也存在于块体内部 ;青藏高原东北缘上地幔P波平均速度低 ,而鄂尔多斯地块的P波平均速度高 ,这与两个地块的地质构造活动特征相吻合 .在青藏高原东北缘与鄂尔多斯地块之间的上地幔存在宽约 2 0 0km的过渡带 ,该过渡带在地表的界限在兰州—海原之间 ,在上地幔表现为向东 4 5°左右的倾斜条带 ,基本结构特征表现为高速与低速物质的混杂 ;青藏高原内部的柴达木地块平均速度偏低 ,而祁连地块的上地幔的平均速度偏高 ,两者相差约 8% ;在泽库、兰州和海原地区的上地幔顶部有明显的低速体侵入特征 .
Combining the data recorded by the portable broadband seismic array across the northeastern edge of the Qinghai-Xizang Plateau and the Ordos area and the travel time data of the regional seismic network, we investigate the P wave velocity structure of the crust and upper mantle down to 400km depth along a profile. Our results show that the structure of the crust and upper mantle along the profile has obviously laterally inhomogeneities, which occur not only between different blocks, but also within block. Along the profile can be identified obvious difference between the velocity structures of the upper mantle beneath the northeastern Qinghai-Xizang and Ordos plateau. The former has a lower averaged P wave velocity than the global model, and the latter is higher than the global model. This is consistent with tectonic activities in these two blocks. Between the northeastern Qinghai-Xizang and Ordos plateau there is a transitional zone of about 200km wide, which has indicators on the surface are Lanzhou and Haiyuan,?respectively.?In?the?upper?mantle?this?transitional zone appears as a sloping strip with about 45° toward the eastern direction. The main features of the transition zone appear as a mixture of high-velocity and low-velocity media. We can also identify the differences of the upper mantle velocity structures beneath the Qaidam basin and the Qilian block within the northeastern Qinghai-Xizang. This appears mainly as a low average velocity in the Qaidam block and a high average velocity in the Qilian block, respectively. The difference between them is up to about 8%. A low-velocity intrusive body is located on the top of the upper mantle beneath Zeko, Lanzhou and the Haiyuan area. This is in accord with the results by the receiver function method.
Combining the data recorded by the portable broadband seismic array across the northeastern edge of the Qinghai-Xizang Plateau and the Ordos area and the travel time data of the regional seismic network, we investigate the P wave velocity structure of the crust and upper mantle down to 400km depth along a profile. Our results show that the structure of the crust and upper mantle along the profile has obviously laterally inhomogeneities, which occur not only between different blocks, but also within block. Along the profile can be identified obvious difference between the velocity structures of the upper mantle beneath the northeastern Qinghai-Xizang and Ordos plateau. The former has a lower averaged P wave velocity than the global model, and the latter is higher than the global model. This is consistent with tectonic activities in these two blocks. Between the northeastern Qinghai-Xizang and Ordos plateau there is a transitional zone of about 200km wide, which has indicators on the surface are Lanzhou and Haiyuan,?respectively.?In?the?upper?mantle?this?transitional zone appears as a sloping strip with about 45° toward the eastern direction. The main features of the transition zone appear as a mixture of high-velocity and low-velocity media. We can also identify the differences of the upper mantle velocity structures beneath the Qaidam basin and the Qilian block within the northeastern Qinghai-Xizang. This appears mainly as a low average velocity in the Qaidam block and a high average velocity in the Qilian block, respectively. The difference between them is up to about 8%. A low-velocity intrusive body is located on the top of the upper mantle beneath Zeko, Lanzhou and the Haiyuan area. This is in accord with the results by the receiver function method.
引文
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[25] 王椿镛,MooneyWD ,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1):1～16WangCY ,MooneyWD ,WangXL ,etal.Studyon3DvelocitystructureofcrustanduppermantleinSichuanYunnanregion,China.ActaSeismologicalSinica(inChinese),2002,24(1):1～16
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[2] 张培震,邓起东,张国民等.中国大陆的强震活动与活动地块.中国科学(D辑),2003,33(增):12～20ZhangPZ ,DengQD ,ZhangGM ,etal.ActivetectonicblocksandstrongearthquakesinthecontinentofChina.ScienceinChina(SeriesD)(inChinese),2003,33(Suppl.):12～20
[3] 李松林,张先康,张成科等.玛沁—兰州—靖边地震测深剖面地壳速度结构的初步研究.地球物理学报,2002,45(2):210～217LiSL ,ZhangXK ,ZhangCK ,etal.ApreliminarystudyonthevelocitystructureofMaq毢nLanzhouJingbianbymeansofdeepseismicsoundingprofile.ChineseJ .Geophys.(inChinese),2002,45(2):210～217
[4] 薛光琦,钱 辉,姜 枚等.青藏高原东北部天然地震探测与岩石圈深部特征.地球学报,2003,24(1):19～26XueGQ ,QianH ,JiangM ,etal.Studiesonthevelocitystructureofcrust uppermantlebeneathNortheastQinghaiTibetPlateau,China.ActaGeoscientiaSinica(inChinese),2003,24(1):19～26
[5] 陈九辉,刘启元,李顺成等.青藏高原东北缘—鄂尔多斯地块地壳上地幔S波速度结构.地球物理学报,2005(待发表)ChenJH ,LiuQY ,LiSC ,etal.CrustanduppermantleS wavevelocitystructureacrossnortheasternTibetanplateauandOrdosblock.ChineseJ .Geophys.(inChinese),2005,inpress
[6] 赵国泽,汤 吉,詹 艳等.青藏高原东北缘地壳电性结构和地块变形关系的研究.中国科学(D辑),2004,(待发表)ZhaoGZ ,TangJ,ZhanY ,etal.RelationbetweenelectricitystructureofthecrustanddeformationofcrustalblocksonthenortheasternmarginofQinghaiTibetPlateau.ScienceinChina(SeriesD)(inChinese),2004,inpress
[7] 徐果明,李光品,王善恩等.用瑞利面波资料反演中国大陆东部地壳上地幔横波速度的三维构造.地球物理学报,2000,43(3):366～376XuGM ,LiGP ,WangSN ,etal.The3DstructureshearwaveinthecrustandmantleofeastcontinentalChinainvertedbyRayleighwavedata.ChineseJ .geophys.(inChinese),2000,43(3):366～376
[8] 何正勤,丁志峰,叶太兰等.中国大陆及其邻域的瑞利波群速度分布图像与地壳上地幔速度结构.地震学报,2002,24(3):253～259HeZQ ,DingZF ,YeTL ,etal.ThegroupvelocitydistributionofRayleighwavesandcrustalanduppermantlevelocitystructureoftheChinesemainlandanditsvicinity.ActaSeismologicaSinica(inChinese),2002,24(3):253～259
[9] 何正勤,丁志峰,叶太兰等.中国大陆及其邻域地壳上地幔速度结构的面波层析成像研究.地震学报,2001,23(6):579～603HeZQ ,DingZF ,YeTL ,etal.SurfacewavetomographyofthecrustanduppermantleofChinesemainland.ActaSeismologicaSinica(inChinese),2001,23(6):579～603
[10] 彭艳菊,苏 伟,郑月军等.中国大陆及海域Love波层析成像.地球物理学报,2002,45(6):792～801PengYJ ,SuW ,ZhengYJ ,etal.LovewaveseismictomographyofChinaandvicinalseaarea.ChineseJ.Geophys.(inChinese),2002,45(6):792～801
[11] 朱良保,许 庆,陈晓非.中国大陆及邻近海域的Rayleigh波群速度分布.地球物理学报,2002,45(4):475～482ZhouLB ,XuQ ,ChenXF .GroupvelocityofRayleighwaveinChinesecontinentanditsadjacentseas.ChineseJ.Geophys.(inChinese),2002,45(4):475～482
[12] 胥 颐,刘福田,刘建华等.中国西北大陆碰撞带的深部特征及其动力学意义.地球物理学报,2001,44(1):40～47XuY ,LiuFT ,LiuJH ,etal.DeepfeaturesofcontinentalcollisionbeltsinnorthwesternChinaandtheirdynamicimplications.ChinesJ .Geophys.(inChinese),2001,44(1):40～47
[13] 刘建华,刘福田,吴 华等.中国南北带地壳和上地幔的三维速度图像.地球物理学报,1989,32(2):143～151LiuJH ,LiuFT ,WuH ,etal.3DvelocityimagesofcrustanduppermantleinChinaSouthNorthseismicbelt.ChineseJ .Geophys.(inChinese),32(2):143～151
[14] 田勤俭,丁国瑜.青藏高原东北隅似三联点构造特征.中国地震,1998,14(4):17～35TianQJ ,DingGY .Thetectonicfeatureofaquasi trijunctioninthenortheasterncornerofQinghaiXizangPlateau.EarthquakeResearchinChina(inChinese),1998,14(4):17～35
[15] 丁国瑜.中国岩石圈动力学概论.北京:地震出版社,1991.438～445DingGY .LithospheresDynamicsofChina.Beijing:SeismologicalPress,1991.438～445
[16] 邓起东,程绍平,闵 伟等.鄂尔多斯块体新生代构造活动和动力学的讨论.地质力学学报,1999,5(3):13～21DengQD ,ChengSP ,MinW ,etal.DiscussiononCenozoictectonicsanddynamicsofOrdosblock.JournalofGeomechanics(inChinese),1999,5(3):12～21
[17] DapengZhao,AkiraHasegawa,HirooKanamori.DeepstructureofJapansubductionzoneasderivedfromlocal,regional,andteleseismicevents.J .Geophys.Res.,1994,99(B11):22313～22329
[18] 刘福田.震源位置和速度结构的联合反演(I)———理论和方法.地球物理学报,1984,27(2):167～175LiuFT .Simultaneousinversionofearthquakehypocentersandvelocitystructure(I) theoryandmethod.ChineseJ .Geophys.(inChinese),1984,27(2):167～175
[19] 刘福田,李 强,吴 华等.用于速度图像重建的层析成像法.地球物理学报,1989,32(1):46～60LiuFT ,LiQ ,WuH ,etal.Seismictomographymethodforreconstructvelocityimages.ChineseJ .Geophys.(inChinese),1989,32(1):46～60
[20] 刘福田,曲克信,吴 华等.华北地区的地震层面成像.地球物理学报,1986,29(5):442～449LiuFT ,QuKX ,WuH ,etal.SeismictomographyofnorthChinaregion.ChineseJ .Geophys.(inChinese),1986,29(5):442～449
[21] 徐佩芬,刘福田,王清晨等.大别—苏鲁碰撞造山带的地震层析成像研究———岩石圈三维速度结构.地球物理学报,2000,43(3):377～385XuPF ,LiuFT ,WangQC ,etal.SeismictomographybeneathDabieSulucollisionorogen3Dvelocitystructurelithosphere.ChineseJ.Geophys.(inChinese),2000,43(3):377～385
[22] ZhaoDapeng,AkiraHasegawa,ShigekiHoriuchi.TomographicimagingofPandSwavevelocitystructurebeneathNortheasternJapan.J.Geophys.Res.,1992,97(B3):19909～19928
[23] ZhaoDapeng,AkiraHasegawa.PwavetomographicimagingofthecrustanduppermantlebeneaththeJapanislands.J.Geophys.Res.,1993,98(B3):4333～4353
[24] 范广伟,WallaceT ,赵大鹏等.应用地震层析成像技术研究深部速度结构.CT理论与应用研究,1999,8(1):1～8FanGW ,WallaceTC ,ZhaoDP ,etal.Aseismicstudyofdeepvelocitystructure.CTTheoryandApplication(inChinese),1999,8(1):1～8
[25] 王椿镛,MooneyWD ,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1):1～16WangCY ,MooneyWD ,WangXL ,etal.Studyon3DvelocitystructureofcrustanduppermantleinSichuanYunnanregion,China.ActaSeismologicalSinica(inChinese),2002,24(1):1～16
[26] 雷建设,周惠兰,赵大鹏.帕米尔及邻区地壳上地幔P波三维速度结构的研究.地球物理学报,2002,45(6):802～811LeiJS ,ZhouHL ,ZhaoDP .3DvelocitystructureofPwaveinthecrustandupper mantlebeneathPamirandadjacentregion.ChineseJ.Geophys.(inChinese),2002,45(6):802～811
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