Crossplot analysis of A.V.O. anomolies in seismic surveying

Seismic imaging apparatus comprising:

• an input for obtaining, for each surface location in a collection of seismic data, successive values from a plurality of seismic attributes data sets, each attribute data set comprising a respective property of said collection of seismic data,
• a windower for grouping the values using a running window of a predetermined length,
• a group parameterizer for calculating from each group of inputs group parameters representative of group behavior of said attribute values within said window, and
• a plotting unit for plotting each of said group as a single point in a space defined by said parameters.

A method of seismic data analysis to provide clustering of A.V.O. data into A.V.O. anomaly types, the method comprising:

• obtaining, for each surface location in a collection of seismic data, successive values of a plurality of seismic attributes data sets, each seismic attribute data set comprising a respective property of said collection of seismic data,
• grouping said values using a running window of a predetermined size into a plurality of groups,
• for each group calculating first and second parameters corresponding to group behavior of said group within said window, and
• plotting each group as a single point, in a space defined by said group parameters, said group parameters having been selected to cause clustering of said seismic reflection events on said plot according to the presence or absence of A.V.O. anomalies.