Research ArticleGEOPHYSICS

Monitoring reservoir response to earthquakes and fluid extraction, Salton Sea geothermal field, California

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Science Advances  10 Jan 2018:
Vol. 4, no. 1, e1701536
DOI: 10.1126/sciadv.1701536
  • Fig. 1 Time-lapse measurements of seismic velocity changes.

    (A) Time history of seismic velocity (dv/v) with two-sigma SDs at five different frequency bands during December 2007 to January 2014. (B and C) Same as (A), but with time interval between February to August 2010 and July to October 2012. EMC, BS, DBC, and OT represent the 2010 Mw 7.2 El Mayor–Cucapah earthquake, the 2012 Brawley seismic swarm, the 30 December 2009 M 5.8 Delta, Baja California, Mexico, and the 15 June 2010 M 5.7 Ocotillo earthquake, respectively (vertical dashed lines). Gray areas indicate time windows in which we were not able to recover empirical Green’s functions (fig. S2 and Materials and Methods).

  • Fig. 2 Stress sensitivity of seismic velocity change.

    Velocity change measured with two-sigma SDs in a frequency range of 0.5 to 2.0 Hz as a function of stress changes inferred from PGV at station RHX. The two-sigma SDs plotted were the median two-sigma SDs in the first 10 days after the target earthquakes (for example, the EMC earthquake). To estimate dynamic stress changes, we used an S-wave velocity of 2.3 km/s and the rigidity of 14 GPa (Materials and Methods). The resultant mean stress sensitivity is −0.0056 MPa−1 (black dashed line), inferred from the EMC earthquake and BS swarm (solid circles). Gray circles show the velocity changes from the DBC and OT earthquakes, and they are not used to compute the stress sensitivity. The inferred stress sensitivity (black dashed line) is extrapolated to the dashed gray lines.

  • Fig. 3 Seismic velocity changes temporally correlated with earthquake swarms.

    (A and B) Inferred seismic velocity changes in the time intervals (A) November to December 2009 and (B) December 2010 to January 2011. Gray bars represent the number of earthquakes per day that occurred within the regions shown in (C) and (D). Dashed lines indicate origin times of M 3+ earthquakes. (C and D) Map views of earthquake swarms. The blue triangles are the locations of the CalEnergy seismic network (EN network). Also shown are the locations of the geothermal injection (red squares) and production wells (white squares) obtained from the California Department of Conservation. Green triangle and diamond are the locations of seismic station RXH [Southern California Seismic (CI) Network] and continuous Global Positioning System (GPS) site P507, respectively. Black dots are relocated earthquake locations with a waveform cross-correlation analysis (77). Yellow stars are locations of M 3+ earthquakes. Earthquakes in the first 100 days from the first earthquake of the earthquake swarms were plotted.

  • Fig. 4 Long-term linear trend of velocity change.

    Values of long-term linear trend of velocity changes in a frequency range of 0.5 to 2.0 Hz obtained from curve fitting (table S1 and Materials and Methods) are shown by the color code in the bottom of the figure. Green rectangle is the SSGF region shown in fig. S1. Background color represents topography.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/e1701536/DC1

    fig. S1. Map view of the seismicity at the SSGF.

    fig. S2. Time delay measurements obtained from EN network at the SSGF.

    fig. S3. Frequency-dependent Rayleigh-wave phase velocity sensitivity.

    fig. S4. Time-lapse measurements of seismic velocity changes inferred from nine components of NCFs.

    fig. S5. Stress changes imparted by the 4 April 2010 Mw 7.2 El Mayor–Cucapah earthquake.

    fig. S6. Stress changes imparted by the 26 August 2012 Mw 5.4 Brawley earthquake.

    fig. S7. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 2010 Mw 7.2 El Mayor–Cucapah earthquake and the 2012 Brawley seismic (BS) swarm.

    fig. S8. Seismic velocity changes, net production, and geodetic line-length change measurements.

    fig. S9. Time history of velocity changes with the single-station cross-correlation analysis.

    fig. S10. Long-term velocity change estimate with curve fitting.

    fig. S11. Long-term velocity change as a function of site elevation.

    fig. S12. Time-lapse measurements of seismic velocity changes at station RXH with the single-station cross-correlation analysis.

    fig. S13. Response of hydrothermal vents to stresses.

    fig. S14. Stress sensitivity for the 2010 Mw 7.2 El Mayor–Cucapah earthquake.

    fig. S15. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 30 December 2009 M 5.8 Delta, Baja California, Mexico and the 15 June 2010 M 5.7 Ocotillo, California earthquakes.

    fig. S16. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 2009 and 2010 earthquake swarms.

    fig. S17. Volumetric static stress change and seismicity map.

    fig. S18. Possible velocity change during the 2005 OB earthquake swarm.

    fig. S19. The November 2009 earthquake swarm.

    fig. S20. The December 2010 earthquake swarm.

    table S1. Parameters of the best-fitting curve to observed seismic velocity changes with Eq. 1 and variance reduction (VR).

    table S2. PGV from the SCEDC and stress sensitivity estimate for the 4 April 2010 Mw 7.2 El Mayor–Cucapah earthquake.

    References (7880)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Map view of the seismicity at the SSGF.
    • fig. S2. Time delay measurements obtained from EN network at the SSGF.
    • fig. S3. Frequency-dependent Rayleigh-wave phase velocity sensitivity.
    • fig. S4. Time-lapse measurements of seismic velocity changes inferred from nine components of NCFs.
    • fig. S5. Stress changes imparted by the 4 April 2010 Mw 7.2 El Mayor–Cucapah earthquake.
    • fig. S6. Stress changes imparted by the 26 August 2012 Mw 5.4 Brawley earthquake.
    • fig. S7. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 2010 Mw 7.2 El Mayor–Cucapah earthquake and the 2012 Brawley seismic (BS) swarm.
    • fig. S8. Seismic velocity changes, net production, and geodetic line-length change measurements.
    • fig. S9. Time history of velocity changes with the single-station cross-correlation analysis.
    • fig. S10. Long-term velocity change estimate with curve fitting.
    • fig. S11. Long-term velocity change as a function of site elevation.
    • fig. S12. Time-lapse measurements of seismic velocity changes at station RXH with the single-station cross-correlation analysis.
    • fig. S13. Response of hydrothermal vents to stresses.
    • fig. S14. Stress sensitivity for the 2010 Mw 7.2 El Mayor–Cucapah earthquake.
    • fig. S15. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 30 December 2009 M 5.8 Delta, Baja California, Mexico and the 15 June 2010 M 5.7 Ocotillo, California earthquakes.
    • fig. S16. Seismic velocity changes, geodetic line-length change, and precipitation measurements around occurrence times of the 2009 and 2010 earthquake swarms.
    • fig. S17. Volumetric static stress change and seismicity map.
    • fig. S18. Possible velocity change during the 2005 OB earthquake swarm.
    • fig. S19. The November 2009 earthquake swarm.
    • fig. S20. The December 2010 earthquake swarm.
    • table S1. Parameters of the best-fitting curve to observed seismic velocity changes with Eq. 1 and variance reduction (VR).
    • table S2. PGV from the SCEDC and stress sensitivity estimate for the 4 April 2010 Mw 7.2 El Mayor–Cucapah earthquake.
    • References (78–80)

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