秦岭造山带与南北相邻地带远震接收函数与地壳结构  

Crust structure of the Qinling orogenic and the region on its north and south margins from teleseismic receiver function

作　　者：司芗[1,2,3] 滕吉文[1] 刘有山[1,2] 马学英[1,2] 乔勇虎[1,2] 董兴鹏[1,2] 宋鹏汉 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学,北京100049 [3]国土资源部油气资源战略研究中心,北京100034

出　　处：《地球物理学报》2016年第4期1321-1334,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(90914012)资助

摘　　要：从2013年3月至2014年11月,我们布设了一条延川—涪陵的流动宽频带地震台阵,剖面由70个流动台站组成,全长约900km,穿越华北克拉通、秦岭—大巴造山带和扬子克拉通东北缘陆内三大构造单元.利用记录到的远震波形资料,提取得到5638个远震P波接收函数,使用H-κ叠加扫描和CCP偏移叠加方法刻划了秦岭造山带与南北相邻地带的地壳厚度、泊松比以及构造界带.研究结果显示,（1）关于地壳厚度：地壳最厚的区域出现在大巴山,地壳厚度集中在47～51km之间,秦岭的地壳厚度相对大巴山较薄,且呈向北减薄趋势,集中在37～46km之间,渭河盆地地壳厚度为本区域最薄地带,在34°N左右处达到最薄为35km,剖面北侧的南鄂尔多斯盆地的地壳厚度变化缓慢,多为44km左右,南侧的四川盆地东北缘的地壳厚度向南缓慢减薄,集中在42～48km之间;（2）关于泊松比：使用接收函数H-κ叠加扫描法得到了沿剖面各台站下方地壳的平均纵、横波速度比VP/VS（κ）,进一步计算得到泊松比σ,泊松比具有明显的横向分块特征,秦岭造山带的泊松比明显低于南北两侧区域,其小于0.26的泊松比表征着该区域地壳物质组分主要为酸性岩石,亦即其酸性长英质组分上地壳相对于基性铁镁质组分下地壳较厚,该区域没有高泊松比分布则表明不存在广泛的部分熔融.（3）关于构造界带：秦岭—大巴造山带与扬子克拉通的边界并非在勉略构造带,应向南移至四川盆地的东北缘,华北克拉通和扬子克拉通分踞秦岭—大巴造山带南、北两侧,且分别以较陡倾角向南和相对较缓的倾角向北俯冲于秦岭—大巴造山带之下,使得秦岭—大巴造山带呈不对称状扇形向外扩展与向上抬升的空间几何模型.秦岭和大巴山之间33°N附近存在分界面,两区域地壳厚度与泊松比特征各异.Qinling-Daba orogenic belt is located between North China craton and the Yangtze craton in an EW narrow zone.As an important part of the central orogenic belt,it is a uniquecomplex typical continental orogenic belt.Studying its crust structure plays an important role for understanding and discussing the interaction among China's Mainland blocks.From March 2013 to November 2014,one seismic profile was deployed crossing the North China craton,Qinling-Daba orogenic belt,and the Yangtze craton,which covered about 900 km from Yanchuan to Fulin and included 70 mobile stations.5638 teleseismic P wave receiver functions were extracted from the waveforms.H-κauto-searching stacking and CCP stacking methods were used to study the crust structure beneath the Qinling orogenic belt and the adjacent north and south zones.Crustal thickness along the profile was obtained by H-κand CCP stacking methods.The average crust velocity ratio VP/VS（κ）beneath each station along the profile was gained by using receiver function H-κstacking method and then the Poisson′s ratio was calculated.The Poisson′s ratio has obvious regional distribution characteristic.Through the CCP stacking methods,the tectonic zone along the profile may be recognized and analyzed.The results indicated,（1）About the crustal thickness：Crustal thickness along Daba mountain is the thickest,which is around 47～51km.While going to the Qinling the thickness becomes thinner,which is around 37～46km.The Weihe basin reaches the thinnest（around 35km）at 34°N.On the north side of profile,i.e.,the south Erdos basin,the crust thickness fluctuates slowly,mostly about 44 km.The thickness of the Sichuan basin northeast margin becomes thinner slowly heading south,mostly about 42～48km.（2）About the Poisson′s ratio：The Poisson′s ratio of Qinling orogenic belt is significantly lower than that of southern and northern area.Qinling′s Poisson′s ratio is less than 0.26,which means that its main crust components are acidic rocks,and its felsic upper cru

关 键 词：秦岭造山带及其南北缘 远震P波接收函数 H-κ叠加 CCP偏移叠加 地壳厚度 泊松比 构造界带 

分 类 号：P315[天文地球—地震学]