Fault activation by hydraulic fracturing in western Canada

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Science  16 Dec 2016:
Vol. 354, Issue 6318, pp. 1406-1409
DOI: 10.1126/science.aag2583

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  1. Fig. 1 Seismicity of northwestern Alberta, Canada, for the period 1985−2016.

    Symbol size indicates magnitude, and color denotes date of occurrence. B.C., British Columbia. Seismicity west of Fox Creek commenced in December 2013 and correlates in space and time with local hydraulic-fracturing operations (9). Focal mechanisms of the largest earthquakes, from (3234), are labeled by year/month/date of occurrence. White rectangle outlines the area in Fig. 2.

  2. Fig. 2 Details of seismicity induced by hydraulic fracturing at six well pads from December 2014 to March 2015.

    Black triangles show local broadband seismograph stations; small black triangle near well pad 1 shows a station that was deployed for a short time after the MW 3.9 event. Event symbols are colored by date of occurrence and are scaled on the basis of magnitude. Well pads are numbered sequentially by initiation of hydraulic-fracturing operations.

  3. Fig. 3 Comparison of seismicity and injection schedules for selected clusters.

    For each cluster (numbered as in Fig. 2), the top shows seismicity (red dots) and calculated maximum magnitude (blue curve) (19); the bottom shows average daily treatment pressure (blue bars) and cumulative injected volume (red curve). Cluster 1 seismicity is repeated as gray dots in other graphs, for timing comparison. Black bar graph at top shows number of events per day for cluster 1, which lacks a typical Omori decay. At well 1, flowback (dashed curve) indicates recovery of only 7% of injected fluid. S1 to S3 indicate time windows for interpreted sequences. A complete set of graphs for all clusters is shown in the supplementary materials (fig. S9).

  4. Fig. 4 Cross section through cluster 1, showing east and west fault strands inferred from double-difference event locations.

    Dark blue symbols show events that occurred during hydraulic fracturing in two horizontal (hz) wells. Light blue, yellow, and red symbols show subsequent events during sequences S1, S2, and S3, respectively.