Beam-steered vertical seismic arrays for wave classification

Vertical seismic profiling (VSP) is a technique for determining wave transmission properties of the earth. It is implemented using a surface energy source and an array of geophones placed vertically in a well shaft. The geophysical interpretation of VSP data is greatly facilitated by the use of geophone array processing or beam steering to separate the various wave types and arrival angles. Constraints are placed on the array directional response pattern to force main lobe and null locations to desired positions. The corrective gradient projection method is then used to determine the set of tap weights which minimize received power subject to the pattern constraints. The algorithm is applied to data from a simulated seismogram with crossing events and to data from a synthetic VSP seismogram for a 2-layer model. These results demonstrate that undesired events from a given direction can be effectively attenuated.