Stress State Inferred From Moment Tensors of Induced Events Near Fox Creek, Alberta: Implications for Fault Criticality

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Using continuous recordings from the ToC2ME field program acquired by the University of Calgary in Fall 2016, we have computed 530 moment tensors of induced seismic events that took place during hydraulic-fracturing operations near Fox Creek, Alberta. Three distinct groups of source mechanisms were identified based on the best double-couple solutions of the retrieved moment tensors, of which two are characterized by predominantly strike-slip motion on sub-vertical nodal planes. One event cluster is characterized by more complex mechanisms, with slip on a shallow-dipping plane accompanied by significant (>30%) non-double-couple components. Stress inversion of this dataset revealed a predominantly strike-slip regime, with S_Hmax in a direction of about N60E. This orientation is in agreement with the nearest available borehole measurement from the World Stress Map but differs from the median regional S_Hmax direction by about 15 degrees. Our analysis indicates that a north-south fault system that hosted most of the M_W> 1.5 events is mis-oriented for slip within the inferred background stress field. Based on our analysis, this fault would require a considerable change in effective stress in order to be brought to a state of incipient failure.

Presenting Author: David W. Eaton

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