Research ArticleEARTHQUAKES

Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable

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Science Advances  02 Aug 2017:
Vol. 3, no. 8, e1700772
DOI: 10.1126/sciadv.1700772
  • Fig. 1 Peak ground acceleration (PGA) measured from the geometric mean of horizontal components recorded by U.S. Geological Survey strong motion instruments for seven recent Mw 4 to 4.5 earthquakes in Oklahoma, Kansas, and Texas (red dots, table S1).

    The predicted ground motions for an Mw 4.5 earthquake (blue solid line) and its 95% confidence interval (gray dashed lines) are calculated using the Ground Motion Prediction Equation (GMPE) from Atkinson (9).

  • Fig. 2 Locations of analyzed earthquakes.
  • Fig. 3 Stress drop estimates of induced and tectonic earthquakes at all depths (top) and deeper than 5 km (bottom) as a function of moment magnitude.

    Dashed lines show the median stress drop for each group. Error bars denote 95% confidence level based on bootstrap analysis.

  • Fig. 4 Stress drop estimates as a function of earthquake depth for strike-slip events and reverse-faulting events.

    Horizontal error bars show bootstrapped 95% confidence level for stress drop. Vertical error bars show the possible range of earthquake depths. The depth gradient of the effective normal stress is 17 MPa/km. Dashed lines indicate fractional stress drops. The top right of the left panel shows the two events with nearly total stress drops: the 2011 Mw 5.0 Prague foreshock and the 2016 Mw 5.8 Pawnee mainshock.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/8/e1700772/DC1

    fig. S1. Observed S-wave spectral ratios of potentially induced earthquakes to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).

    fig. S2. Observed S-wave spectral ratios of tectonic earthquakes in the central United States to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).

    fig. S3. Observed S-wave spectral ratios of tectonic earthquakes in eastern North America to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).

    fig. S4. East-component velocity seismograms and spectra recorded at station KAN06 for the 2016 Mw 5.1 Fairview earthquake (event #1) and its eGf (event #3).

    fig. S5. East-component velocity seismograms and spectra recorded at station OK033 for the 2016 Mw 5.1 Fairview earthquake (event #1) and its eGf (event #3).

    fig. S6. The misfits between the Brune spectral model and the stacked spectral ratios, and the corner frequency estimates derived from different window lengths for the 2016 Mw 5.1 Fairview earthquake.

    fig. S7. Histograms of the corner frequency distribution from the bootstrap analysis for four Oklahoma earthquakes.

    table S1. Near-source peak ground accelerations of potentially induced earthquakes in the central United States.

    table S2. Source parameters of potentially induced earthquakes in the central United States.

    table S3. Source parameters of tectonic earthquakes in the central United States.

    table S4. Source parameters of tectonic earthquakes in eastern North America.

    table S5. Comparison of source parameters between the study of Boyd et al. (41) and this study.

    table S6. Networks and number of stations used in this study.

    References (4759)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Observed S-wave spectral ratios of potentially induced earthquakes to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).
    • fig. S2. Observed S-wave spectral ratios of tectonic earthquakes in the central United States to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).
    • fig. S3. Observed S-wave spectral ratios of tectonic earthquakes in eastern North America to their eGfs (colored solid lines) and modeled spectral ratios (gray dashed lines).
    • fig. S4. East-component velocity seismograms and spectra recorded at station KAN06 for the 2016 Mw 5.1 Fairview earthquake (event #1) and its eGf (event #3).
    • fig. S5. East-component velocity seismograms and spectra recorded at station OK033 for the 2016 Mw 5.1 Fairview earthquake (event #1) and its eGf (event #3).
    • fig. S6. The misfits between the Brune spectral model and the stacked spectral ratios, and the corner frequency estimates derived from different window lengths for the 2016 Mw 5.1 Fairview earthquake.
    • fig. S7. Histograms of the corner frequency distribution from the bootstrap analysis for four Oklahoma earthquakes.
    • table S1. Near-source peak ground accelerations of potentially induced earthquakes in the central United States.
    • table S2. Source parameters of potentially induced earthquakes in the central United States.
    • table S3. Source parameters of tectonic earthquakes in the central United States.
    • table S4. Source parameters of tectonic earthquakes in eastern North America.
    • table S5. Comparison of source parameters between the study of Boyd et al. (41) and this study.
    • table S6. Networks and number of stations used in this study.
    • References (47–59)

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