Method for facilitating monitoring, in the course of time, of the evolution of an underground zone by compared analysis of various seismic record sets

1) A method for detecting physical changes undergone in the course of time by a subsoil zone, by analysis of changes observable on seismic events characterised each by seismic attributes, recorded within a time window, on seismic traces of several data sets obtained respectively during successive seismic surveys, comprising using a pattern recognition technique to classify the seismic events, with formation of a learning base with several classes and construction of a classification function for the seismic events, characterized in that it comprises:

• forming an analysis set comprising all the seismic events recorded on the traces of the various seismic trace sets obtained during the successive seismic surveys, with identification of each one by means of its spatial position in said zone and by the number of the trace set to which it belongs,
• forming a learning base comprising several learning classes comprising each a certain number of seismic events detected from all the successive seismic surveys, that can be associated with common physical properties,
• constructing a calibrated classification function on said defined learning classes, and
• applying to all of the seismic events detected from all the successive seismic surveys the calibrated classification function so as to assign at least part of the seismic events of said set to the various learning classes.