FIRST ARRIVAL PICKING ON COMMON‐OFFSET TRACE COLLECTIONS FOR AUTOMATIC ESTIMATION OF STATIC CORRECTIONS*

The increase in the number of geophone groups in production records during recent years and the requirement for accurate basic static corrections for high resolution records have made it necessary to develop sufficiently accurate automatic techniques for the determination of static corrections.

A fully automatic method is presented which makes use of the delay‐time method in order to compute static corrections at each shot position. Delay times, weathering and subweathering velocities are determined from automatic picks of the first arrivals on common‐offset trace collections.

It is assumed that the weathering is a single layer and that the dip of the subweathering layer under the geophone groups is small.

The picking routine is fully automatic and successful in most cases, provided the signal‐to‐noise ratio is sufficiently high.

The subsequent filtering of erroneous values for picked times is performed by means of statistical techniques, using curves of picked times on common‐offset trace collections. If the distance between receivers and shot‐points on the profile is sufficiently short, one can expect only little change in the picked times of two contiguous traces.

The method is well adapted to end‐on spreads with a great number of traces, where distances between geophone groups are short.

Examples are presented showing the possibilities of the method for the determination of long wavelength as well as short wavelength components of static corrections.