Analysis of reduced traveltime creates nonlinear delay-time solution

Abstract

This case study utilizes time-arrival picks and a two-layer depth/velocity model to enhance the refraction solution using nonlinear refractor velocities. The near surface has rapidly changing topography and thickness of the low-velocity layer. The refractor velocity is varying due to outcropping limestone horizons. The acquisition of the 3D survey is hampered due to inaccessible terrain with cliffs up to 150 m in height. There are two large areas with source omissions due to irrigated cultivations. For this 3D seismic survey, multiple tests applying tomographic modeling fail to resolve the near-surface anomaly. The starting model for this analysis is a linear reciprocal-path delay-time model. The proposed method redetermines the delay time, taking into account the nonlinear refractor velocity. The enhancement produced near-surface static corrections that improved the imaging of the 3D seismic volume and created an analytical tool of the solutions uncertainty.