论文部分内容阅读
利用中法1995年布设在跨过阿尔金断裂剖面上的18个流动三分量地震台站记录到的近5个月的天然地震记录,经筛选得到533个高质量接收函数。通过速度分析和接收函数成像处理,得到了阿尔金断裂附近地壳结构的清晰图像。塔里木盆地的Moho界面非常清楚,近水平地位于~44km深度上。该界面以低缓的角度一直向南延伸到了阿尔金断裂附近的~70km的深度。阿尔金断裂以南柴达木盆地下面的Moho界面也十分清楚,近水平地位于~55km的深度上,在阿尔金断裂附近存在向上挠曲,并抬升到了~45km的深度上。在阿尔金断裂下方,Moho界面存在~15km的错断。塔里木盆地Moho之下还存在另一个震相,我们解释为沉积层多次波与可能来自Hales间断面转换波的复合震相。接收函数成像结果表明阿尔金断裂是一个超壳的岩石圈断裂,具有比较直立的产状和很狭窄的剪切变形带。根据这些结果,我们推测塔里木的下地壳可能要比柴达木的下地壳更硬,柴达木地壳增厚的原因可以部分归结于它有一个相对弱的下地壳,青藏高原隆升没有扩展到塔里木盆地是因为塔里木盆地具有更刚性的下地壳和岩石圈地幔。高原北部地壳变形应该是所谓青藏高原隆升的“硬”变形模式(Tapponnieretal.,2001)和“软”变形模式(EnglandandHouseman,1989;ClarkandRoyden,2000)共同作用的结果。
Based on the natural seismograms recorded by China-France in 1995 for 18 flowing three-component seismic stations spanning the Altun fault profile, 533 high-quality receiver functions were screened. A clear image of the crustal structure near the Altyn Tagh fault is obtained through velocity analysis and receiver function imaging. The Moho interface in the Tarim Basin is very clear and lies almost horizontally at a depth of ~ 44 km. The interface extends gently to the south to a depth of ~ 70 km near the Altyn Tagh fault. The Moho interface beneath the Qaidam basin to the south of the Altyn Tagh fault is also well known, lying almost horizontally at a depth of ~ 55 km. There is upward deflection near the Altyn Tagh fault and uplift to a depth of ~ 45 km. Below the Altun fault, a ~ 15km fault was observed at the Moho interface. There is another seismic facies beneath the Moho in the Tarim Basin, which we interpret as the complex facies of sedimentary multifractal and possibly Hales intercept converted waves. The receiver function imaging results show that the Altyn Tagh fault is a superhuman lithospheric fault with relatively upright and very narrow shear deformation bands. Based on these results, we speculate that the lower crust of Tarim may be harder than the lower crust of Qaidam. The reason for the thickening of the Qaidam crust may be attributed in part to the fact that it has a relatively weak lower crust and the uplift of the Qinghai-Tibet Plateau does not extend to The Tarim Basin is due to the more rigid lower crust and lithospheric mantle in the Tarim Basin. The crustal deformation in the northern plateau should be the result of the so-called “hard” deformation mode of the so-called Qinghai-Tibet Plateau uplift (Tapponnieretal. 2001) and the “soft” deformation mode (England and Houseman, 1989; Clark and Royden, 2000).