青藏高原东北缘噪声层析成像研究
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摘要
利用青海、甘肃和宁夏3个区域地震台网两年的波形数据,通过地动噪声层析成像方法给出了青藏高原东北缘8—40 s的瑞雷面波二维群速度结构和三维地壳上地幔顶部的剪切波速度结构。研究结果显示,相比传统的面波层析成像方法,噪声层析成像给出的短周期面波信息能够较好地约束地壳和上地幔顶部结构。8 s和10 s周期的群速度图像与沉积层和基底结晶深度有关,具体而言:祁连山和西秦岭造山带表现为高速体特征,柴达木盆地、河西走廊和鄂尔多斯西缘表现为低速特征;周期为15 s和20 s的瑞雷面波群速度图像反映的是中地壳结构,15 s周期群速度图像上造山带下方高速体向北和向东方向扩展,20 s周期群速度图像呈现大范围低速体,推测为中下地壳低速层影响所致;30 s和40 s周期的群速度图像反映的是莫霍面深度附近的速度结构,具体表现为青藏高原大范围的低速体,向北和向东逐渐表现为高速体,说明青藏高原的莫霍面深度较深,且向北和向东逐渐减薄。另外,三维剪切波速度结构显示祁连地块和甘孜地块中地壳存在大范围低速层,且由柴达木盆地东侧深部的低速层连接,该低速层可能是青藏高原物质北移的一个通道。
Two years of seismic ambient noise observed by three provincial networks are used to estimate 2D Rayleigh wave group velocity and 3 D shear wave velocity structure of northeastern Tibetan Plateau. Compared with traditional surface wave tomography,ambient noise tomography may provide refined structure of the crust and uppermost mantle. Low group velocities of 8 s and 10 s periods coincide with sedimentary layer and crystalline basement,while the high velocity zones denote igneous cores of the major mountain ranges. Qilian mountain and Qinling mountain show high velocity,but Qaidam basin,Hexi corridor of Gansu Province and western Ordos block show low velocity. 15 s and 20 s period group velocities represent the structure of middle crust,and the high velocity zones expand to north and east in 15 s period group velocity map. Whereas in the 20 s period group velocity map most areas show low velocity anomaly,which may correspond to the low velocity crustal layer revealed by previous studies. 30 s and40 s period group velocity maps represent the velocity structure around the depth of Moho. The velocity maps show low velocity zones in Tibetan Plateau and high velocity towards the north and the east,suggesting that the crust is thick in Tibetan Plateau and thinned in the northern and the eastern studied areas. In addition,3D shear velocity structure shows low velocity zone beneath Qilian orogen and Garze terrain. The two zones are connected by a lower crustal low velocity zone to the east of Qaidam basin,which may be a channel of northward material movement.
Two years of seismic ambient noise observed by three provincial networks are used to estimate 2D Rayleigh wave group velocity and 3 D shear wave velocity structure of northeastern Tibetan Plateau. Compared with traditional surface wave tomography,ambient noise tomography may provide refined structure of the crust and uppermost mantle. Low group velocities of 8 s and 10 s periods coincide with sedimentary layer and crystalline basement,while the high velocity zones denote igneous cores of the major mountain ranges. Qilian mountain and Qinling mountain show high velocity,but Qaidam basin,Hexi corridor of Gansu Province and western Ordos block show low velocity. 15 s and 20 s period group velocities represent the structure of middle crust,and the high velocity zones expand to north and east in 15 s period group velocity map. Whereas in the 20 s period group velocity map most areas show low velocity anomaly,which may correspond to the low velocity crustal layer revealed by previous studies. 30 s and40 s period group velocity maps represent the velocity structure around the depth of Moho. The velocity maps show low velocity zones in Tibetan Plateau and high velocity towards the north and the east,suggesting that the crust is thick in Tibetan Plateau and thinned in the northern and the eastern studied areas. In addition,3D shear velocity structure shows low velocity zone beneath Qilian orogen and Garze terrain. The two zones are connected by a lower crustal low velocity zone to the east of Qaidam basin,which may be a channel of northward material movement.
引文
陈九辉,刘启元,李顺成,郭飙,赖院根.2005.青藏高原东北缘-鄂尔多斯地块地壳上地幔S波速度结构[J].地球物理学报,48(2):333-342.Chen J H,Liu Q Y,Li S C,Guo B,Lai Y G.2005.Crust and upper mantle S-wave velocity structure across northeastern Tibetan Plateau and Ordos block[J].Chinese Journal of Geophysics,48(2):333-342(in Chinese).
郭桂红,张智,程建武,董治平,闫建萍,马亚维.2015.青藏高原东北缘地壳各向异性的构造含义[J].地球物理学报,58(11):4092-4105.Guo G H,Zhang Z,Cheng J W,Dong Z P,Yan J P,Ma Y W.2015.Seismic anisotropy in the crust in northeast margin of Tibetan Plateau and tectonic implication[J].Chinese Journal of Geophysics,58(11):4092-4105(in Chinese).
嘉世旭,张先康.2008.青藏高原东北缘深地震测深震相研究与地壳细结构[J].地球物理学报,51(5):1431-1443.Jia S X,Zhang X K.2008.Study on the crust phases of deep seismic sounding experiments and fine crust structures in the northeast margin of Tibetan Plateau[J].Chinese Journal of Geophysics,51(5):1431-1443(in Chinese).
李永华,吴庆举,安张辉,田小波,曾融生,张瑞青,李红光.2006.青藏高原东北缘地壳S波速度结构与泊松比及其意义[J].地球物理学报,49(5):1359-1368.Li Y H,Wu Q J,An Z H,Tian X B,Zeng R S,Zhang R Q,Li H G.2006.The Poisson ratio and crustal structure across the NETibetan Plateau determined from receiver functions[J].Chinese Journal of Geophysics,49(5):1359-1368(in Chinese).
刘启民,赵俊猛,卢芳,刘宏兵.2014.用接收函数方法反演青藏高原东北缘地壳结构[J].中国科学:地球科学,44(4):668-679.Liu Q M,Zhao J M,Lu F,Liu H B.2014.Crustal structure of northeastern margin of the Tibetan Plateau by receiver function inversion[J].Science China Earth Sciences,57(4):741-750.
王琼,高原,石玉涛,吴晶.2013.青藏高原东北缘上地幔地震各向异性:来自SKS、PKS和SKKS震相分裂的证据[J].地球物理学报,56(3):892-905.Wang Q,Gao Y,Shi Y T,Wu J.2013.Seismic anisotropy in the uppermost mantle beneath the northeastern margin of QinghaiTibet Plateau:Evidence from shear wave splitting of SKS,PKS and SKKS[J].Chinese Journal of Geophysics,56(3):892-905(in Chinese).
杨志高,张雪梅.2016.2016年门源MS6.4地震震区地壳厚度及波速比研究[J].地震研究,39(4):566-573.Yang Z G,Zhang X M.2016.Study on crustal thickness and velocity ratio near Menyuan MS6.4 earthquake zone[J].Journal of Seismological Research,39(4):566-573(in Chinese).
余大新,李永华,吴庆举,潘佳铁,张风雪,何静.2014.利用Rayleigh波相速度和群速度联合反演青藏高原东北缘S波速度结构[J].地球物理学报,57(3):800-811.Yu D X,Li Y H,Wu Q J,Pan J T,Zhang F X,He J.2014.S-wave velocity structure of the northeastern Tibetan Plateau from joint inversion of Rayleigh wave phase and group velocities[J].Chinese Journal of Geophysics,57(3):8 0 0-811(in Chinese).
赵金仁,李松林,张先康,杨卓欣,张成科,刘宝峰,张建狮,潘素珍.2005.青藏高原东北缘莫霍界面的三维空间构造特征[J].地球物理学报,48(1):78-85.Zhao J R,Li S L,Zhang X K,Yang Z X,Zhang C K,Liu B F,Zhang J S,Pan S Z.2005.Three dimensional Moho geometry beneath the northeast edge of the Qinghai-Tibet Plateau[J].Chinese Journal of Geophysics,48(1):78-85(in Chinese).
Bao X W,Song X D,Xu M J,Wang L S,Sun X X,Mi N,Yu D Y,Li H.2013.Crust and upper mantle structure of the North China Craton and the NE Tibetan Plateau and its tectonic implications[J].Earth Planet Sci Lett,369/370:129-137.
Bensen G D,Ritzwoller M H,Barmin M P,Levshin A L,Lin F,Moschetti M P,Shapiro N M,Yang Y.2007.Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J].Geophys J Int,169(3):1239-1260.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow[J].Geology,28(8):703-706.
Fang H J,Yao H J,Zhang H J,Huang Y C,van der Hilst R D.2015.Direct inversion of surface wave dispersion for three-dimensional shallow crustal structure based on ray tracing:Methodology and application[J].Geophys J Int,201(3):1251-1263.
Herrmann R B,Ammon C J.2002.Computer programs in seismology[EB/OL].Version 3.15.[2016-12-12].http://www.eas.slu.edu/eqc/eqccps.html.
Jiang C X,Yang Y J,Zheng Y.2014.Penetration of mid-crustal low velocity zone across the Kunlun fault in the NE Tibetan Plateau revealed by ambient noise tomography[J].Earth Planet Sci Lett,406:81-92.
Laske G,Ma Z T,Masters G,Pasyanos M.2015.Crust1.0:A new global crustal model at 1×1 degrees[EB/OL].[2016-12-12].http://igppweb.ucsd.edu/~gabi/crust1.html.
Li H Y,Shen Y,Huang Z X,Li X F,Gong M,Shi D N,Sandvol E,Li A B.2014.The distribution of the mid-to-lower crustal low-velocity zone beneath the northeastern Tibetan Plateau revealed from ambient noise tomography[J].J Geophys Res,119(3):1954-1970.
Li L,Li A B,Shen Y,Sandvol E A,Shi D N,Li H Y,Li X F.2013.Shear wave structure in the northeastern Tibetan Plateau from Rayleigh wave tomography[J].J Geophys Res,118(8):4170-4183.
Li X F,Santosh M,Cheng S H,Xu X M,Zhong W X.2015.Crustal structure and composition beneath the northeastern Tibetan Plateau from receiver function analysis[J].Phys Earth Planet Inter,249:51-58.
Pan S Z,Niu F L.2011.Large contrasts in crustal structure and composition between the Ordos Plateau and the NE Tibetan Plateau from receiver function analysis[J].Earth Planet Sci Lett,303(3/4):291-298.
Rawlinson N,Sambridge M.2004a.Multiple reflection and transmission phases in complex layered media using a multistage fast marching method[J].Geophysics,69(5):1338-1350.
Rawlinson N,Sambridge M.2004b.Wave front evolution in strongly heterogeneous layered media using the fast marching method[J].Geophys J Int,156(3):631-647.
Rawlinson N,Sambridge M.2005.The fast marching method:An effective tool for tomographic imaging and tracking multiple phases in complex layered media[J].Explor Geophys,36(4):341-350.
Tapponnier P,Xu Z Q,Roger F,Meyer B,Arnaud N,Wittlinger G,Yang J S.2001.Oblique stepwise rise and growth of the Tibet Plateau[J].Science,294(5547):1671-1677.
Wessel P,Smith W H F,Scharroo R,Luis J,Wobbe F.2013.Generic Mapping Tools:Improved version released[J].Eos Trans Am Geophys Union,94(45):409-410.
Yang Y J,Ritzwoller M H,Levshin A L,Shapiro N M.2007.Ambient noise Rayleigh wave tomography across Europe[J].Geophys J Int,168(1):259-274.
Zhang P Z,Shen Z K,Wang M,Gan W J,Bürgmann R,Molnar P,Wang Q,Niu Z J,Sun J Z,Wu J C,Sun H R,You X Z.2005.Continuous deformation of the Tibetan Plateau from global positioning system data[J].Geology,32(9):809-812.
Zheng D,Li H Y,Shen Y,Tan J,Ouyang L B,Li X F.2016.Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions[J].Geophys J Int,204(1):583-590.
Zhu L P,Helmberger D V.1998.Moho offset across the northern margin of the Tibetan Plateau[J].Science,281(5380):1170-1172.
郭桂红,张智,程建武,董治平,闫建萍,马亚维.2015.青藏高原东北缘地壳各向异性的构造含义[J].地球物理学报,58(11):4092-4105.Guo G H,Zhang Z,Cheng J W,Dong Z P,Yan J P,Ma Y W.2015.Seismic anisotropy in the crust in northeast margin of Tibetan Plateau and tectonic implication[J].Chinese Journal of Geophysics,58(11):4092-4105(in Chinese).
嘉世旭,张先康.2008.青藏高原东北缘深地震测深震相研究与地壳细结构[J].地球物理学报,51(5):1431-1443.Jia S X,Zhang X K.2008.Study on the crust phases of deep seismic sounding experiments and fine crust structures in the northeast margin of Tibetan Plateau[J].Chinese Journal of Geophysics,51(5):1431-1443(in Chinese).
李永华,吴庆举,安张辉,田小波,曾融生,张瑞青,李红光.2006.青藏高原东北缘地壳S波速度结构与泊松比及其意义[J].地球物理学报,49(5):1359-1368.Li Y H,Wu Q J,An Z H,Tian X B,Zeng R S,Zhang R Q,Li H G.2006.The Poisson ratio and crustal structure across the NETibetan Plateau determined from receiver functions[J].Chinese Journal of Geophysics,49(5):1359-1368(in Chinese).
刘启民,赵俊猛,卢芳,刘宏兵.2014.用接收函数方法反演青藏高原东北缘地壳结构[J].中国科学:地球科学,44(4):668-679.Liu Q M,Zhao J M,Lu F,Liu H B.2014.Crustal structure of northeastern margin of the Tibetan Plateau by receiver function inversion[J].Science China Earth Sciences,57(4):741-750.
王琼,高原,石玉涛,吴晶.2013.青藏高原东北缘上地幔地震各向异性:来自SKS、PKS和SKKS震相分裂的证据[J].地球物理学报,56(3):892-905.Wang Q,Gao Y,Shi Y T,Wu J.2013.Seismic anisotropy in the uppermost mantle beneath the northeastern margin of QinghaiTibet Plateau:Evidence from shear wave splitting of SKS,PKS and SKKS[J].Chinese Journal of Geophysics,56(3):892-905(in Chinese).
杨志高,张雪梅.2016.2016年门源MS6.4地震震区地壳厚度及波速比研究[J].地震研究,39(4):566-573.Yang Z G,Zhang X M.2016.Study on crustal thickness and velocity ratio near Menyuan MS6.4 earthquake zone[J].Journal of Seismological Research,39(4):566-573(in Chinese).
余大新,李永华,吴庆举,潘佳铁,张风雪,何静.2014.利用Rayleigh波相速度和群速度联合反演青藏高原东北缘S波速度结构[J].地球物理学报,57(3):800-811.Yu D X,Li Y H,Wu Q J,Pan J T,Zhang F X,He J.2014.S-wave velocity structure of the northeastern Tibetan Plateau from joint inversion of Rayleigh wave phase and group velocities[J].Chinese Journal of Geophysics,57(3):8 0 0-811(in Chinese).
赵金仁,李松林,张先康,杨卓欣,张成科,刘宝峰,张建狮,潘素珍.2005.青藏高原东北缘莫霍界面的三维空间构造特征[J].地球物理学报,48(1):78-85.Zhao J R,Li S L,Zhang X K,Yang Z X,Zhang C K,Liu B F,Zhang J S,Pan S Z.2005.Three dimensional Moho geometry beneath the northeast edge of the Qinghai-Tibet Plateau[J].Chinese Journal of Geophysics,48(1):78-85(in Chinese).
Bao X W,Song X D,Xu M J,Wang L S,Sun X X,Mi N,Yu D Y,Li H.2013.Crust and upper mantle structure of the North China Craton and the NE Tibetan Plateau and its tectonic implications[J].Earth Planet Sci Lett,369/370:129-137.
Bensen G D,Ritzwoller M H,Barmin M P,Levshin A L,Lin F,Moschetti M P,Shapiro N M,Yang Y.2007.Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J].Geophys J Int,169(3):1239-1260.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow[J].Geology,28(8):703-706.
Fang H J,Yao H J,Zhang H J,Huang Y C,van der Hilst R D.2015.Direct inversion of surface wave dispersion for three-dimensional shallow crustal structure based on ray tracing:Methodology and application[J].Geophys J Int,201(3):1251-1263.
Herrmann R B,Ammon C J.2002.Computer programs in seismology[EB/OL].Version 3.15.[2016-12-12].http://www.eas.slu.edu/eqc/eqccps.html.
Jiang C X,Yang Y J,Zheng Y.2014.Penetration of mid-crustal low velocity zone across the Kunlun fault in the NE Tibetan Plateau revealed by ambient noise tomography[J].Earth Planet Sci Lett,406:81-92.
Laske G,Ma Z T,Masters G,Pasyanos M.2015.Crust1.0:A new global crustal model at 1×1 degrees[EB/OL].[2016-12-12].http://igppweb.ucsd.edu/~gabi/crust1.html.
Li H Y,Shen Y,Huang Z X,Li X F,Gong M,Shi D N,Sandvol E,Li A B.2014.The distribution of the mid-to-lower crustal low-velocity zone beneath the northeastern Tibetan Plateau revealed from ambient noise tomography[J].J Geophys Res,119(3):1954-1970.
Li L,Li A B,Shen Y,Sandvol E A,Shi D N,Li H Y,Li X F.2013.Shear wave structure in the northeastern Tibetan Plateau from Rayleigh wave tomography[J].J Geophys Res,118(8):4170-4183.
Li X F,Santosh M,Cheng S H,Xu X M,Zhong W X.2015.Crustal structure and composition beneath the northeastern Tibetan Plateau from receiver function analysis[J].Phys Earth Planet Inter,249:51-58.
Pan S Z,Niu F L.2011.Large contrasts in crustal structure and composition between the Ordos Plateau and the NE Tibetan Plateau from receiver function analysis[J].Earth Planet Sci Lett,303(3/4):291-298.
Rawlinson N,Sambridge M.2004a.Multiple reflection and transmission phases in complex layered media using a multistage fast marching method[J].Geophysics,69(5):1338-1350.
Rawlinson N,Sambridge M.2004b.Wave front evolution in strongly heterogeneous layered media using the fast marching method[J].Geophys J Int,156(3):631-647.
Rawlinson N,Sambridge M.2005.The fast marching method:An effective tool for tomographic imaging and tracking multiple phases in complex layered media[J].Explor Geophys,36(4):341-350.
Tapponnier P,Xu Z Q,Roger F,Meyer B,Arnaud N,Wittlinger G,Yang J S.2001.Oblique stepwise rise and growth of the Tibet Plateau[J].Science,294(5547):1671-1677.
Wessel P,Smith W H F,Scharroo R,Luis J,Wobbe F.2013.Generic Mapping Tools:Improved version released[J].Eos Trans Am Geophys Union,94(45):409-410.
Yang Y J,Ritzwoller M H,Levshin A L,Shapiro N M.2007.Ambient noise Rayleigh wave tomography across Europe[J].Geophys J Int,168(1):259-274.
Zhang P Z,Shen Z K,Wang M,Gan W J,Bürgmann R,Molnar P,Wang Q,Niu Z J,Sun J Z,Wu J C,Sun H R,You X Z.2005.Continuous deformation of the Tibetan Plateau from global positioning system data[J].Geology,32(9):809-812.
Zheng D,Li H Y,Shen Y,Tan J,Ouyang L B,Li X F.2016.Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions[J].Geophys J Int,204(1):583-590.
Zhu L P,Helmberger D V.1998.Moho offset across the northern margin of the Tibetan Plateau[J].Science,281(5380):1170-1172.