Crustal velocity structure beneath the northern North-South Seismic Zone from local seismic tomography and its tectonic implications
-
摘要: 收集和拾取了“中国地震科学台阵”探测项目在南北地震带北段布设的680个流动地震台站和中国地震台网217个固定台站所记录的地震事件的P波和S波初至到时，通过层析成像研究获得了南北地震带北段水平网格间距为0.33°×0.33°的地壳P波和S波速度分布。结果显示：在30 km深度上青藏高原东北部表现为显著的整体性低速异常，低速异常区向南延伸至龙门山断裂，以106°E为界线将秦岭造山带分为西侧的低速异常和东侧的高速异常，并沿银川—河套地堑向东北展布，向北穿过河西走廊，在阿拉善地块表现为低速异常，这可能暗示了青藏高原向东的扩展被较为坚固的四川盆地和秦岭造山带阻挡，而向北的扩展可能影响到了河西走廊至阿拉善地块，并沿银川—河套地堑影响到鄂尔多斯西北缘；在50 km深度上，阿拉善地块、祁连造山带东段显示高速异常，有可能是阿拉善地块向祁连东段下方俯冲所致。研究区内大部分地震分布在P波和S波高低速异常相间及速度剧烈变化的地区，M≥6.0强震几乎全部投影在30 km深度的低速异常区域内，说明强震发生的背景可能与地震源区下方的低速区有关。Abstract: We collected and picked the first arrivals of P and S waves of local and regional events recorded by 680 portable broadband seismic stations of the ChinArray-Himalaya Ⅱ and 217 fixed stations of the Chinese Seismic Network located on the northern North-South Seismic Zone （96°E−110°E, 30°N−44°N）. We got a 3D P and S wave velocity （vP and vS） structure of the crust beneath the northern North-South Seismic Zone with a horizontal grid space of 0.33°×0.33° by tomography. The tomography results reveal obvious integrated low velocity anomalies at 30 km depth beneath the northeastern Tibetan Plateau. The low velocity zone extends southward to the Longmenshan fault and extends eastward to the 106°E, dividing the Qinling orogenic belt into low velocity zone at westside and high velocity zone at eastside. The low velocity zone also extends northeast along the Yinchuan-Hetao graben, and extends northward through the Hexi Corridor, and it shows low velocity anomalies beneath the Alxa block at 30 km depth. This implicates that the extension of the Tibetan Plateau may be blocked by the relatively strong Sichuan basin and Qinling block in the east, while the extension affects the Hexi Corridor and the Alashan block, as well as the northwestern margin of Ordos along the Yinchuan-Hetao graben. At 50 km depth, it shows high velocity anomalies beneath the Alxa block and eastern Qilian orogenic belt, indicating possible southward subduction of the Alxa block beneath the eastern Qilian orogenic belt. Most crustal earthquakes in the studied region generally occurred along the fault zones between low velocity and high velocity zones where vP and vS change drastically over a short distance. The projections of large earthquakes （M≥6.0） at 30 km depth are almost located in the low velocity zone, which may indicate that the background of strong earthquakes is related to the low velocity zone beneath the source area.
-
-
![]()
图 5 走时残差直方图
Figure 5. Histograms of travel-time residuals for the earthquakes used in this study
![]()
图 7 速度扰动变化与走时残差均方根之间的折中曲线. 灰色实心圆圈中的数字为本研究采用的最佳反演参数
（a） 采用不同阻尼因子的折中曲线；（b） 采用不同平滑参数的折中曲线
Figure 7. Trade-off curve for the norm of solution and RMS travel time residual. The numbers in solid gray circles denote the optimal parameters.
（a） The curve with different damping parameters; （b） The curve with different smoothing parameters
![]()
图 6 初始一维速度模型（a）及本文采用的地壳厚度分布（b）（引自Li et al，2014b ；Wang et al，2017a ）
Figure 6. 1-D starting velocity model （a） and crustal thickness obtained from results of receiver functions （b） （after Li et al，2014b ；Wang et al，2017a ）
![]()
图 10 不同深度上穿过每个格点的vP （左）和vS （右）的射线条数
Figure 10. Distribution of vP （left） and vS （right） rays numbers passing through each grid node at different depths
![]()
图 8 不同深度处0.5°水平间隔情况下 vP （左）和vS （右）的检测板测试结果
Figure 8. Results of a checkboard resolution test of vP （left） and vS （right） with the lateral grid interval of 0.5° at different depths
![]()
图 9 不同深度处0.33°水平间隔情况下vP （左）和vS （右）的检测板测试结果
Figure 9. Results of a checkboard resolution test of vP （left） and vS （right） with the lateral grid interval of 0.33° at different depths
-
毕奔腾,胡祥云,李丽清,张恒磊,刘双,蔡建超. 2016. 青藏高原东北部多尺度重力场及其地球动力学意义[J]. 地球物理学报,59(2):543–555. doi: 10.6038/cjg20160213 Bi B T,Hu X Y,Li L Q,Zhang H L,Liu S,Cai J C. 2016. Multi-scale analysis to the gravity field of the northeastern Tibetan Pla-teau and its geodynamic implications[J].Chinese Journal of Geophysics,59(2):543–555 (in Chinese) doi: 10.6038/cjg20160213
常利军,丁志峰,王椿镛. 2016. 南北构造带北段上地幔各向异性特征[J]. 地球物理学报,59(11):4035–4047 doi: 10.6038/cjg20161109 Chang L J,Ding Z F,Wang C Y. 2016. Upper mantle anisotropy beneath the northern segment of the north-south tectonic belt in China[J]. Chinese Journal of Geophysics,59(11):4035–4047 (in Chinese) doi: 10.6038/cjg20161109
邓起东,张培震,冉勇康,杨晓平,闵伟,陈立春. 2003. 中国活动构造与地震活动[J]. 地学前缘,10(增刊1):66–73 Deng Q D,Zhang P Z,Ran Y K,Yang X P,Min W,Chen L C. 2003. Active tectonics and earthquake activities in China[J]. Earth Science Frontiers,10(S1):66–73 (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)
嘉世旭, 郭文斌, 林吉焱, 王夫运, 段永红. 2017. 青藏高原东北缘地壳深部结构长剖面深地震测深探测研究[R]. 北京: 中国地球科学联合学术年会2017: 360–361. Jia S X, Guo W B, Lin J Y, Wang F Y, Duan Y H. 2017. Study on the Crust Structure of Long Profile Deep Seismic Sounding Experiments in the Northeast Margin of Tibetan Plateau[R]. Beijing: Annual Meeting of Chinese Geoscience Union (CGU) 2017: 360–361 （in Chinese）.
李英康,高锐,米胜信,姚聿涛,高建伟,李文辉,熊小松. 2014. 青藏高原东北缘六盘山—鄂尔多斯盆地的地壳速度结构特征[J]. 地质论评,60(5):1147–1157 Li Y K,Gao R,Mi S X,Yao Y T,Gao J W,Li W H,Xiong X S. 2014. The characteristics of crustal velocity structure for Liupan Mountain−Ordos Basin in the northeastern margin of Qinghai−Xizang (Tibet) Plateau[J]. Geological Review,60(5):1147–1157 (in Chinese)
刘永前,方小敏,宋春晖,李立立,程彧. 2009. 青藏高原东北缘六盘山地区新生代构造旋转及其意义[J]. 大地构造与成矿学,33(2):189–198 Liu Y Q,Fang X M,Song C H,Li L L,Cheng Y. 2009. Cenozoic tectonic rotation of the Liupanshan region in the northeastern Tibetan Plateau and its implications[J]. Geotectonica et Metallogenia,33(2):189–198 (in Chinese)
裴顺平. 2017. 青藏高原东北缘上地壳Pg波速度和各向异性联合成像及其动力学意义[R]. 北京: 中国地球科学联合学术年会2017: 366. Pei S P. 2017. Join Imaging of Pg Velocity and Anisotropy of Upper Crust Beneath the Northeast Margin of Tibetan Plateau and its Dynamics Implications[R]. Beijing: Annual Meeting of Chinese Geoscience Union (CGU) 2017: 366 （in Chinese）.
王敏,沈正康,牛之俊,张祖胜,孙汉荣,甘卫军,王琪,任群. 2003. 现今中国大陆地壳运动与活动块体模型[J]. 中国科学:D辑,33(增刊1):21–32 Wang M,Shen Z K,Niu Z J,Zhang Z S,Sun H R,Gan W J,Wang Q,Ren Q. 2003. Contemporary crustal deformation of the Chinese continent and tectonic block model[J]. Science in China:Series D,46(S2):25–40
王帅军,刘保金,嘉世旭,邓晓果,宋向辉,李怡青. 2017. 利用人工地震测深剖面研究银川盆地及两侧区域的S波速度结构[J]. 地球物理学进展,32(5):1936–1943 doi: 10.6038/pg20170510 Wang S J,Liu B J,Jia S X,Deng X G,Song X H,Li Y Q. 2017. Study on S-wave velocity structure difference of Yinchuan basin and blocks on both sides using artificial seismic sounding profiles[J]. Progress in Geophysics,32(5):1936–1943 (in Chinese) doi: 10.6038/pg20170510
王兴臣,丁志峰,武岩,朱露培. 2017. 中国南北地震带北段及其周缘地壳厚度与泊松比研究[J]. 地球物理学报,60(6):2080–2090 Wang X C,Ding Z F,Wu Y,Zhu L P. 2017. Crustal thickness and Poisson’s ratios beneath the northern section of the north-south seismic belt and surrounding areas in China[J]. Chinese Journal of Geophysics,60(6):2080–2090 (in Chinese)
王绪本,罗威,张刚,蔡学林,覃庆炎,罗皓中. 2013. 扇形边界条件下的龙门山壳幔电性结构特征[J]. 地球物理学报,56(8):2718–2727 doi: 10.6038/cjg20130820 Wang X B,Luo W,Zhang G,Cai X L,Qin Q Y,Luo H Z. 2013. Electrical resistivity structure of Longmenshan crust-mantle under sector boundary[J]. Chinese Journal of Geophysics,56(8):2718–2727 (in Chinese) doi: 10.6038/cjg20130820（inChinese）
喻学惠,赵志丹,莫宣学,周肃,朱德勤,王永磊. 2005. 甘肃西秦岭新生代钾霞橄黄长岩的40Ar/39Ar同位素定年及其地质意义[J]. 科学通报,50(23):2638–2643 Yu X H,Zhao Z D,Mo X X,Zhou S,Zhu D Q,Wang Y L. 2006. 40Ar/39Ar dating for Cenozoic kamafugite from western Qinling in Gansu Province[J]. Chinese Science Bulletin,51(13):1621–1627
詹艳,赵国泽,王立凤,王继军,陈小斌,赵凌强,肖骑彬. 2014. 西秦岭与南北地震构造带交汇区深部电性结构特征[J]. 地球物理学报,57(8):2594–2607 doi: 10.6038/cjg20140819 Zhan Y,Zhao G Z,Wang L F,Wang J J,Chen X B,Zhao L Q,Xiao Q B. 2014. Deep electric structure beneath the intersection area of west Qinling orogenic zone with North-South seismic tectonic zone in China[J]. Chinese Journal of Geophysics,57(8):2594–2607 (in Chinese) doi: 10.6038/cjg20140819（inChinese）
詹艳,杨皓,赵国泽,赵凌强,孙翔宇. 2017. 青藏高原东北缘海原构造带马东山阶区深部电性结构特征及其构造意义[J]. 地球物理学报,60(6):2371–2384 doi: 10.6038/cjg20170627 Zhan Y,Yang H,Zhao G Z,Zhao L Q,Sun X Y. 2017. Deep electrical structure of crust beneath the Madongshan step area at the Haiyuan fault in the northeastern margin of the Tibetan Plateau and tectonic implications[J]. Chinese Journal of Geophysics,60(6):2371–2384 (in Chinese) doi: 10.6038/cjg20170627（inChinese）
张乐天,金胜,魏文博,叶高峰,段书新,董浩,张帆,谢成良. 2012. 青藏高原东缘及四川盆地的壳幔导电性结构研究[J]. 地球物理学报,55(12):4126–4137 doi: 10.6038/j.issn.0001-5733.2012.12.025 Zhang L T,Jin S,Wei W B,Ye G F,Duan S X,Dong H,Zhang F,Xie C L. 2012. Electrical structure of crust and upper mantle beneath the eastern margin of the Tibetan Plateau and the Sichuan basin[J]. Chinese Journal of Geophysics,55(12):4126–4137 (in Chinese) doi: 10.6038/j.issn.0001-5733.2012.12.025（inChinese）
张培震,邓起东,张国民,马瑾,甘卫军,闵伟,毛凤英,王琪. 2003. 中国大陆的强震活动与活动地块[J]. 中国科学:D辑,33(增刊1):12–20 Zhang P Z,Deng Q D,Zhang G M,Ma J,Gan W J,Min W,Mao F Y,Wang Q. 2003. Active tectonic blocks and strong earthquakes in the continent of China[J]. Science in China:Series D,46(S2):13–24
赵盼盼,陈九辉,刘启元,郭飚,李顺成,李昱. 2015. 龙门山断裂带中上地壳速度结构的短周期环境噪声成像[J]. 地球物理学报,58(11):4018–4030 doi: 10.6038/cjg20151111 Zhao P P,Chen J H,Liu Q Y,Guo B,Li S C,Li Y. 2015. Fine structure of middle and upper crust of the Longmenshan fault zone from short period seismic ambient noise[J]. Chinese Journal of Geophysics,58(11):4018–4030 (in Chinese) doi: 10.6038/cjg20151111（inChinese）
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
Cheng B,Zhao D P,Cheng S Y,Ding Z T,Zhang G W. 2016. Seismic tomography and anisotropy of the Helan-Liupan tectonic belt:Insight into lower crustal flow and seismotectonics[J]. J Geophys Res,121(4):2608–2635
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
Dayem K E,Molnar P,Clark M K,Houseman G A. 2009. Far-field lithospheric deformation in Tibet during continental collision[J]. Tectonics,28(6):TC6005 doi: 10.1029/2008TC002344
Ding Z T,Cheng B,Dong Y P,Zhao D P. 2017. Seismic imaging of the crust and uppermost mantle beneath the Qilian orogenic belt and its geodynamic implications[J]. Tectonophysics,705:63–79
Gan W, Zhang P, Shen Z K, Niu Z, Wang M, Wan Y, Zhou D, Cheng J. 2007. Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[J]. J Geophys Res,112:B08416
Hickman S,Sibson R H,Bruhn R. 1995. Introduction to special section:Mechanical involvement of fluids in faulting[J]. J Geophys Res,100(B7):12831–12840
Huang Z C,Zhao D P,Wang L S. 2011. Stress field in the 2008 Iwate-Miyagi earthquake (M7.2) area[J]. Geochem Geophys Geosyst,12(6):Q06006 doi: 10.1029/2011GC003626
Jiang C X,Yang Y J,Zheng Y. 2014. Penetration of mid-crustal low velocity zone across the Kunlun fault in the NE Tibetan Pla-teau revealed by ambient noise tomography[J]. Earth Planet Sci Lett,406:81–92
Lei J S,Zhao D P. 2009. Structural heterogeneity of the Longmenshan fault zone and the mechanism of the 2008 Wenchuan earthquake (MS8.0)[J]. Geochem Geophys Geosyst,10(10):Q10010 doi: 10.1029/2009GC002590
Li H Y,Shen Y,Huang Z X,Li X F,Gong M,Shi D N,Sandvol E,Li A B. 2014a. 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 doi: 10.1002/2013JB010374
Li Y H,Gao M T,Wu Q J. 2014b. Crustal thickness map of the Chinese mainland from teleseismic receiver functions[J]. Tectonophysics,611:51–60
Li Y H,Pan J T,Wu Q J,Ding Z F. 2017a. Lithospheric structure beneath the northeastern Tibetan Plateau and the western Sino-Korea craton revealed by Rayleigh wave tomography[J]. Geophys J Int,210(2):570–584 doi: 10.1093/gji/ggx181
Li Y H,Wang X C,Zhang R Q,Wu Q J,Ding Z F. 2017b. Crustal structure across the NE Tibetan Plateau and Ordos block from the joint inversion of receiver functions and Rayleigh-wave dispersions[J]. Tectonophysics,705:33–41
Liu Q Y,van der Hilst R D,Li Y,Yao H J,Chen J H,Guo B,Qi S H,Wang J,Huang H,Li S C. 2014. Eastward expansion of the Tibetan Plateau by crustal flow and strain partitioning across faults[J]. Nat Geosci,7(5):361–365
Lu H J,Xiong S F. 2009. Magnetostratigraphy of the Dahonggou section,northern Qaidam basin and its bearing on Cenozoic tecto-nic evolution of the Qilianshan and Altyn Tagh fault[J].Earth Planet Sci Lett,288(3/4):539–550
Mulch A,Chamberlain C P. 2006. The rise and growth of Tibet[J]. Nature,439(7077):670–671
Paige C C,Saunders M A. 1982. LSQR:An algorithm for sparse linear equations and sparse least squares[J]. ACM Trans Math Softw,8(1):43–71
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
Royden L H,Burchfiel B C,King R W,Wang E,Chen Z L,Shen F,Liu Y P. 1997. Surface deformation and lower crustal flow in eastern Tibet[J]. Science,276(5313):788–790
Shen X Z,Yuan X H,Ren J S. 2015. Anisotropic low-velocity lower crust beneath the northeastern margin of Tibetan Plateau:Evi-dence for crustal channel flow[J]. Geochem Geophys Geosyst,16(12):4223–4236 doi: 10.1002/2015GC005952
Sibson R H. 1992. Implications of fault-valve behaviour for rupture nucleation and recurrence[J]. Tectonophysics,211(1/4):283–293
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
Wang W L,Wu J P,Fang L H,Lai G J,Cai Y. 2017a. Sedimentary and crustal thicknesses and Poisson's ratios for the NE Tibetan Plateau and its adjacent regions based on dense seismic arrays[J]. Earth Planet Sci Lett,462:76–85
Wang X B,Zhang G,Fang H,Luo W,Zhang W,Zhong Q,Cai X L,Luo H Z. 2014. Crust and upper mantle resistivity structure at middle section of Longmenshan,eastern Tibetan Plateau[J]. Tectonophysics,619/620:143–148
Wang X C,Li Y H,Ding Z F,Zhu L P,Wang C Y,Bao X W,Wu Y. 2017b. Three dimensional lithospheric S wave velocity mo-del of the NE Tibetan Plateau and western North China Craton[J]. J Geophys Res,122(8):6703–6720 doi: 10.1002/2017JB014203
Wang Z,Zhao D,Wang J. 2010. Deep structure and seismogenesis of the north-south seismic zone in southwest China[J]. J Geophys Res,115:B12334 doi: 10.1029/2010JB007797
Wu Z B,Xu T,Badal J,Yao H J,Wu C L,Zhang Z J,Teng J W. 2017. Crustal shear-wave velocity structure of northeastern Tibet revealed by ambient seismic noise and receiver functions[J]. Gondwana Res,41:400–410
Wu Z B,Xu T,Liang C T,Wu C L,Liu Z Q. 2018. Crustal shear wave velocity structure in the northeastern Tibet based on the Neighbourhood algorithm inversion of receiver functions[J]. Geophys J Int,212(3):1920–1931
Yang Y J,Ritzwoller M H,Zheng Y,Shen W S,Levshin A L,Xie Z J. 2012. A synoptic view of the distribution and connecti-vity of the mid-crustal low velocity zone beneath Tibet[J]. J Geophys Res,117(B4):B04303 doi: 10.1029/2011JB008810
Ye Z,Gao R,Li Q S,Zhang H S,Shen X Z,Liu X Z,Gong C. 2015. Seismic evidence for the North China plate underthrus-ting beneath northeastern Tibet and its implications for plateau growth[J]. Earth Planet Sci Lett,426:109–117
Yin A,Harrison T M. 2000. Geologic evolution of the Himalayan-Tibetan orogen[J]. Annu Rev Earth Planet Sci,28(1):211–280
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. 2004. Continuous deformation of the Tibetan Plateau from global positioning system data[J]. Geology,32(9):809–812
Zhang Q,Sandvol E,Ni J,Yang Y J,Chen Y J. 2011. Rayleigh wave tomography of the northeastern margin of the Tibetan Pla-teau[J]. Earth Planet Sci Lett,304(1/2):103–112
Zhao D P,Hasegawa A,Horiuchi S. 1992. Tomographic imaging of P and S wave velocity structure beneath northeastern Japan[J]. J Geophys Res,97(B13):19909–19928
Zhao D P,Hasegawa A,Kanamori H. 1994. Deep structure of Japan subduction zone as derived from local,regional,and teleseismic events[J]. J Geophys Res,99(B11):22313–22329
Zhao D P. 2015. Multiscale Seismic Tomography[M]. New York: Springer: 304.
Zhao L F,Xie X B,He J K,Tian X B,Yao Z X. 2013. Crustal flow pattern beneath the Tibetan Plateau constrained by regional Lg-wave Q tomography[J]. Earth Planet Sci Lett,383:113–122
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
下载:
计量
- 文章访问数: 1849
- HTML全文浏览量: 1132
- PDF下载量: 151
