Method for verifying the location of an array of detectors

A method for relocating, relative to a geodetic datum, the nominal positions of the members of an array of seismic detectors, the detectors being in communication with a signal processing system, comprising:

• a) depositing a plurality of detectors in an array at nominal locations, D.sub.i ;
• b) causing an acoustic source to visit each one of a plurality of geographically-known source locations SR.sub.j, and to launch an acoustic wavefield therefrom;
• c) determining a set of nominal ranges, R.sup.n.sub.i,j between every known source location, SR.sub.j, and every nominal detector location, D.sub.i ;
• d) at each wavefield launching, measuring, with said signal processing system, the minimum wavefield travel time between every known source location and every nominal detector location, taken in all combinations, to define a set of pick times, P.sub.i,j corresponding to said set of nominal ranges R.sup.n.sub.i,j ;
• e) with the aid of the signal processing system, fitting a global polynomial regression curve of the R.sup.n.sub.i,j on the P to provide a set of pick time distances (ptd) with the global vertical velocity gradient removed;
• f) using the known source coordinates, the nominal detector coordinates and the set of pick time distances, with the aid of the signal processing system, generating a quadratic surface to provide a common block containing the coefficients for modeling the lateral velocity gradient;
• g) simultaneously calculating a network of updated local detector coordinates using the common-block coefficients;
• h) comparing the updated detector coordinates with the nominal detector coordinates;
• i) repeating steps f) through h) until the difference between the nominal and the updated detector coordinates for every detector in said array converge to a preselected limit.