f A HYBRID METHOD FOR FIRST BREAK AUTO PICKING

First break picking is a basic procedure in first arrival tomography. There are a few of first break auto picking approaches available, such as energy ratio, AIC, and tracking. These methods work well with noise free data, but applied to field data, none of them are robust and large bias from the desired picks may present. A hybrid auto picking method is proposed. It first uses the energy ratio to generate a sketch of T-X curve, from which a velocity versus offset function is built, then employs AIC approach with the search range limited by the velocity versus offset function, finally adjusts the picks by correlation of the wavelet of adjacent traces. This method is proven by lots of experiments with a variety of data in refraction and cross-well tomography.