ADAPTIVE PICKING OF REFRACTED FIRST ARRIVALS1

Static correction computations require knowledge of the refracted traveltimes. Zero-phase wavelet sources cannot be picked reliably when incoherent picking techniques are used. Assuming a complex convolutional model for Vibroseis, a coherent picking technique based on the matched filter is described. In order to match the filter to the first arrival wavelet an adaptive algorithm is used. This allows the filter to change both with shot and offset so that all the properties of matched filtering such as improvement of S/N and resolution can be exploited. Incoherent picking is used before coherent picking to improve the convergence of adaptive picking.