使用回折波走时数据的起伏地表速度建模方法  

A Method for Building Velocity Model Using Traveltimes of Diving-Waves Observed on Undulant Surface

作　　者：何万利 杨华臣[1] 张建中[1] He Wanli;Yang Huachen;Zhang Jianzhong(The Key Laboratory of Submarine Geosciences and Prospecting Techniques, Ministry of Education, College of Marine Geosciences, Ocean University of China, Qingdao 266100, China)

机构地区：[1]中国海洋大学海洋地球科学学院,海底科学与探测技术教育部重点实验室,山东青岛266100

出　　处：《中国海洋大学学报（自然科学版）》2021年第9期64-70,共7页Periodical of Ocean University of China

基　　金：山东省自然科学基金项目(ZR2019MD001)资助。

摘　　要：传统的走时层析方法依赖于初始速度模型,需要射线追踪计算,速度建模效率低。常规的回折波走时反演方法速度建模效率较高,但通过对走时曲线拟合获取射线参数,受地形起伏和走时误差的影响很大,速度建模精度较低。为兼顾近地表速度建模的效率与精度,本文改进了回折波走时方程,提出一种基于回折波走时方程的起伏地表速度建模方法。该方法将每一个共中心点道集按偏移距大小进行选排并分段,在每一个偏移距段内,先利用回折波走时方程逐道计算相应的回折点位置和速度,再对各个炮检对的计算结果进行最小二乘拟合及反距离加权,获得统计平均回折点位置和速度值。对每个共中心点道集均做上述处理,从而建立近地表速度模型。理论模型测试和实测资料应用验证了本文方法的正确性和实用性。The traditional traveltime tomography that relies on the initial velocity model requires ray tracing,resulting in low efficiency of velocity model building.The current traveltime inversion methods which use traveltime equations of diving waves have high efficiency.However,the ray parameters obtained by fitting the traveltime curve are not accurate enough due to undulant topography and traveltime errors.Taking the efficiency and the accuracy of the velocity model building into account,a new method based on modified traveltime equations of the diving waves is proposed for constructing near-surface velocity model with the rugged observation surface in this paper.The common-midpoint gathers are divided into some segment according to offset.In an offset-segment,the positions of the turning points and the corresponding velocities are calculated using the observed first-arrival traveltime data.The statistical average position of those turning points and the corresponding velocity at the position are computed using the least-square fitting and inverse distance weighting.The positions of all turning points and corresponding velocities can be obtained using all common-midpoint gathers.Thus,the near-surface velocity model can be acquired using interpolation methods.The test on theoretical model verifies the superiority of the proposed method.Finally,the proposed method is applied to the field seismic data acquired in a mountain area,demonstrating its practicability.

关 键 词：近地表 速度建模 回折波 初至走时 静校正 

分 类 号：P631.4[天文地球—地质矿产勘探]