Atlantic Richfield Company

Mary J Cole

Robert J Withers

Shirley A Rieven

A system and computer program for determining the location of a seismic event in an earth formation zone using seismic traces corresponding to the event collected from one or more sensors in the zone. A graphical data window is displayed of the seismic traces corresponding to the event, the traces representing observed arrival time signals from the sensors plotted with respect to time. A window of a base map of the positions of the sensors within the zone is also displayed. Displayed in the data window is a curve plotting calculated arrival time signals for the traces, the curve being developed from a user-selected one of the observed arrival time signals displayed in the data window and from a user-selected trial location of the event selected in the base map window. The program enables user-repositioning of the trial location in the base map window such that the displayed curve moves in correspondence with the repositioning of the trial location. The trial location is repositioned until an acceptable visual coincidence of the curve is reached with the observed arrival time signals of the traces to thereby yield the location of the event. The program includes a pick-mode technique to refine the location of the event and a polarization analysis to remove ambiguity in the location of the event when more than one solution is possible.

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Plano, TX, United States of America

Mary J Cole