复杂山前带地震初至拾取方法应用研究

Study on the application of seismic first arrival pickup method in complex piedmont

复杂山前带表层结构在纵、横向上变化剧烈,单炮能量弱,背景噪声发育,信噪比低,地震初至难以准确拾取。为了提高初至拾取精度及效率,针对单炮初至难以准确识别及初至拾取范围不明确等问题,开展波动方程正演、可控震源预处理及不同初至范围层析反演分析等方面工作。结果表明,波动方程正演模拟方法指导地震单炮的初至拾取,可以避免初至漏拾、错拾现象;可控震源单炮开展最小相位化和反褶积处理,近道初至识别率提高50%以上,可提高单炮初至信噪比;初至偏移距涵盖风化层及1 km左右的折射层时间范围即可满足层析反演精度需求。通过以上方法处理,采用相同的地震资料处理流程及层析反演参数,可以提高静校正精度,改善剖面的成像效果,具有一定推广价值。

In the complex piedmont zone,the surface structure changes dramatically in the vertical and horizontal direction.Due to the weak energy of single shot,lots of background noise,and the low SNR,it is difficult to pick up the seismic first arrival accurately.In order to improve the accuracy and efficiency of first arrival pickup,wave equation forward modeling,vibroseis pretreatment and tomographic inversion analysis with different first arrival ranges are carried out to solve the problems such as difficulty in first arrival identification and unclear pickup range of single shot.The results show that the wave equation forward modeling method can guide the first arrival pickup of single shot,and can avoid missing and wrong pickup of first arrival.With the minimum phasing and deconvolution processing of vibroseis single shot,the recognition rate of near path first arrival can be improved by more than 50%,and the SNR of single shot first arrival can also be improved.The first arrival offset range,which covers the time of weathering layer and refraction layer of about 1 km,can meet the needs of tomographic inversion accuracy.Through the above method by using the same seismic data processing procedure and tomographic inversion parameters,not only the static correction accuracy but also the imaging effect of the profile can be improved,which has a certain value of popularization.