The Plus-minus time analysis method and its implementation

Jocelyn Dufour, Darren S. Foltinek

The Plus-Minus time analysis method, which is based on the plus-minus method of Hagedorn (1959), was developed to solve the time delays of reflection seismic data. The time delays are caused by low velocity near-surface deposits. The Plus-Minus time analysis method includes a Plus time analysis for depth analysis and a Minus time analysis for velocity determination. The method is based on the traveltime reciprocity and the determination of the crossover point. The crossover point determination uses the traveltime difference analysis of Lawton (1989) and the branch point analysis of Wang and Cheadle (1995). The use of all the possible overlapping shot spreads in the Plus time analysis allows and statistical analysis. The Plus-Minustime analysis was coded in the Matlab language and tested with a synthetic dataset. The Plus-Minus time analysis method provides a reliable near-surface model with accurate depths and velocities.