三维起伏地形下回折波快速走时层析及其静校正应用

    Fast first-arrival traveltime tomography of diving waves under rugged surface and its application to static correction

    • 摘要: 基于射线追踪的初至走时层析被广泛用于近地表速度建模,解决复杂近地表地震资料的静校正问题。该方法需要进行射线追踪计算初至波路径和多次迭代更新初始速度模型,导致其应用于实测三维高密度地震资料时存在耗时极大的问题。为此,本文提出一种在三维起伏地形下利用回折波走时信息快速建立近地表速度模型的方法。基于起伏地形下速度在纵、横向变化时的回折波走时及射线方程,采用共偏移距数据集自地表向下逐层确定介质的速度分布。该方法无需射线追踪和迭代更新速度模型,具有很高的建模效率。理论模型数据测试验证了本文方法的有效性。将该方法应用于三维实测地震资料,取得了和菲涅尔体初至走时层析方法相当的静校正效果,且显著提高了计算效率。

       

      Abstract: Ray tracing-based first-arrival traveltime tomography is widely used to construct near-surface velocity models to achieve the static correction of seismic data from complex near surface.However,this method necessitates the calculation of ray paths for first-arrival traveltimes and the iterative updating of initial velocity models.As a result,significant computational time is required when applying this method to measured 3D high-density seismic data.To address this issue,this study proposed a method for quickly building 3D near-surface velocity models utilizing diving wave traveltimes under rugged surface.Specifically,based on the ray and traveltime equations of diving waves corresponding to velocities subjected to lateral and vertical changes under rugged surface,the velocity distribution from the observation surface downward was determined using common offset gathers.The proposed method eliminates the need for ray tracing and iterative updates of initial velocity models,offering high modeling efficiency.Tests based on data from theoretical models verified the effectiveness of the proposed method.When applied to measured 3D seismic data,the proposed method yielded static correction results comparable to those obtained using the Fresnel-volume first-arrival traveltime tomography while significantly improving computational efficiency.

       

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