Abstract

From July 1980 to August 1984, the University of Western Ontario operated a small seismic telemetry network over the Gobles oil field in Southwestern Ontario. A total of 478 small earth tremors, mainly in the 1 to 2 magnitude range were detected by this array. There were three events greater than magnitude 3 felt by residents up to 15 km from the oil field. Approximately 10 events/month were recorded on average, although the actual number was rather erratic and tended to have a winter maximum. Event locations did not correlate with the actual positions of the oil and gas wells in the field but rather are confined to two main areas, one lying 1.5 km northwest of the town of Gobles and the other just south of the town. The depths of the well-recorded events were found to be near the depth of the producing horizon. The observed first motion patterns indicated that at least two active faults almost perpendicular to each other are present in the area. The results are consistent with the hypothesis that the events are induced or triggered by fluids which are pumped in and out of wells during secondary recovery activities.

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