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在地表附近,有一段地震波传播速度较低的低速层和降速层。低降速层的厚度一般变化很大。从降速层底面开始,平均速度随着深度增加而按某种规律比较稳定地增加。由于低降速层的存在,使反射波到达时间畸变。表层校正的任务就是消除低降速层对反射时间的影响。黄土覆盖地区,不仅在原、梁、峁上存在低降速层,在沟里低、降速层的影响同样不可忽视。尤其是在构造幅度很小的黄土地区,为了准确地反映地下的构造形态,因此,在黄土地区进行地震勘探就必须十分重视表层校正工作。
In the vicinity of the surface, there is a low-velocity and velocity-lowering layer with a lower seismic velocity. The thickness of the low velocity layer generally varies widely. Starting from the bottom of the deceleration layer, the average velocity increases steadily by some law as the depth increases. Due to the existence of low velocity layer, the reflected wave arrival time distortion. The task of surface correction is to eliminate the effect of low velocity layer on the reflection time. Loess areas, not only in the original, beam, 峁 on the existence of low-speed layer, low in the ditch, the same effect of deceleration layer can not be ignored. Especially in the loess area with small structure amplitude, in order to accurately reflect the subsurface structure and shape, seismic surveying in the loess area must attach great importance to surface correction.