Reconsidering the aim and function of low-velocity zone investigation in the massive deserts of middle Tarim basin

Small refraction and upholes are the main technologies for low-velocity zone investigation in the massive deserts of middle Tarim basin, which aim at obtaining the near-surface velocity model for the source depth design and datum statics calculation. Source depth of massive deserts in middle Tarim basin is generally designed 1 to 3 meters under the water table and it is easy to obtain the burial depth of water table by small refraction and uphole. However, the calculation of field statics should obtain the detailed velocity distribution of all layers above substitution velocity (2000 m/s). For the effect of acquisition density and investigation depth, the field statics obtained by small refraction and uphole exist a big error and the stacking profiles after field statics has a long wavelength static problem. This problem was effectively solved by using nonlinear first break tomography inversion static method to take the place of the small refraction and uphole. Finally, aimed at the steady water table in massive deserts of middle Tarim basin, the feasibility of only identifying the depth of water table in the area with low-velocity zone was discussed, indicating that it can largely decrease the density of investigation points.