Technical CommentsSeismology

Response to Comment on “How will induced seismicity in Oklahoma respond to decreased saltwater injection rates?”

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Science Advances  09 Aug 2017:
Vol. 3, no. 8, eaao2277
DOI: 10.1126/sciadv.aao2277


  • Fig. 1 Observation and prediction of induced seismicity in north-central Oklahoma.

    The monthly number of observed earthquakes (M ≥ 3, green; M ≥ 3.5, red) (aftershocks of M ≥ 4.7 events have been removed), complete earthquake catalogs (gray dashed lines), seismogenic index (SI) models calibrated to different times between June 2014 and December 2015 (dotted lines), predicted decay rates according to Omori’s law (p = 2) (black solid lines), and seismicity rates resulting from the suggested parameter range by Goebel et al. (gray areas). The figure is an updated version of Fig. 4 presented in Langenbruch and Zoback (2) and includes seismicity in the region subjected to injection rate reduction mandated in early 2016. The eight month of earthquake data (October 2016 to May 2017) has been recorded after our forecast was accepted for publication.

  • Fig. 2 Comparison of observed, expected, and forecasted magnitude distributions.

    (A) The complete earthquake catalog (M ≥ 3) from January 2009 to May 2017 (solid line) and the magnitude distribution expected from our model in the same time window. (B) The magnitude distribution of earthquakes (solid line) recorded from October 2016 to May 2017 after our forecast (dashed line) was accepted for publication. (C) Observed and forecasted magnitude distributions for 2017 (January to May). Magnitude distribution resulting from the “realistic parameter choice” suggested by Goebel et al. [gray shaded areas in (B) and (C)] disagree with observations.

  • Fig. 3 Expected, observed, and forecasted M ≥ 4.5 and M ≥ 5 earthquakes.

    (A) Observed M ≥ 5 earthquakes (solid lines) occur within the 95% confidence interval (shaded areas) around the model expectation (dashed lines). The 95% confidence interval is computed according to a Poisson process. Occurrence of four M ≥ 5 earthquakes through May 2017 was expected. (B) Forecasted occurrence probabilities of M ≥ 5 and M ≥ 4.5 from 2017 to 2022. Our model expects 1.21 M ≥ 5 earthquakes but accounts for the possibility of zero (30%), one (36%), two (22%), or three (9%) M ≥ 5 earthquakes within the 95% confidence interval.