1. A method for classifying AVO anomalies in near-offset and far-offset seismic data volumes, comprising the steps of: (a) calculating a plurality of initial AVO seismic attributes in the near-offset and far-offset seismic data volumes; (b) constructing a probabilistic neural network from the calculated initial AVO seismic attributes; (c) calculating AVO anomaly classifications in a portion of the near-offset and far-offset seismic data volumes, using the constructed probabilistic neural network; (d) repeating steps (a) through (c) until the calculated AVO anomaly classifications in the portion of the near-offset and far-offset seismic data volumes are satisfactory; and (e) calculating AVO anomaly classifications throughout the near-offset and far-offset seismic data volumes, using the constructed probabilistic neural network.