高级检索

    地震资料揭示的塔里木盆地地壳结构特征

    Seismic evidence for new characteristics of the crustal structure in the Tarim Basin, northwest China

    • 摘要: 本文利用纵波速度结构剖面来刻画塔里木盆地地壳结构特征,搜集盆地范围内14000余条纵波速度资料,采用层析成像方法,生成18条沿经度线剖面和9条沿纬度线剖面。结果表明,在盆地范围内,Moho界面整体隆升,并因热上涌作用形成局部凸起。Moho界面下方约20 km范围内,波速变化较为复杂。在Moho界面之上,以6.8 km/s速度线为界,该速度线以下,其速度线形态基本与Moho界面一致,而该速度线以上,上部为盆地盖层对应的平缓递变带,下部则出现速度异常体,其中高速带分布基本与盆地范围相当,仅在盆地北缘延伸至天山之下;高速核则仅出现在北纬39°以北的范围内,可以为南−北塔里木拼贴提供佐证。以6.8 km/s速度线为界,塔里木盆地地壳具有“两分性”,上部地壳虽波速变化较复杂,但上、下地壳厚度比小于1,说明地壳大部分属于波速高、密度大、刚性强的物质,为现今可能发生的陆内“A”型俯冲提供了物质基础。

       

      Abstract: This paper utilizes P-wave velocity structural profiles to characterize the crustal structural features of the Tarim Basin. Over 14,000 P-wave velocity data points within the basin area were collected, and through the application of tomographic methods, 18 profiles along longitudinal lines and 9 profiles along latitudinal lines were generated. The Moho interface is generally uplifted within the basin, containing local bulges caused by thermal upwelling. Within the area spanning approximately 20 km below the Moho interface, the wave velocity variations are relatively complex. Taking the 6.8 km/s velocity contour as the boundary, the velocity contours below primarily align with the Moho interface, while above this contour, the upper part corresponds to a gently grading zone of the basin cover. It is in the lower part that velocity anomalies appear. The high-velocity zones are primarily distributed within the basin area, extending only under the northern edge of the basin to the Tianshan Mountains; high-velocity cores only appear north of 39°N, providing a potential source of evidence for the South and North Tarim plate collision. The 6.8 km/s velocity contour boundary causes the crust of the Tarim Basin to exhibit a “dichotomous” nature. Although the P-wave velocity variations in the upper crust are complex, the thickness ratio of the upper to lower crust is below 1, indicating that most of the crust consists of materials with high wave velocity, high density, and high rigidity, providing the material basis for possible modern intracontinental “A”-type subduction.

       

    /

    返回文章
    返回