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

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.