Research ArticleGEOLOGY

Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle

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Science Advances  15 Mar 2017:
Vol. 3, no. 3, e1602642
DOI: 10.1126/sciadv.1602642
  • Fig. 1 Earthquake location and P- and S-source time functions.

    (A) Map of the seismic stations (triangles) used here and location of the 21 September 2013 Wyoming earthquake (star) and its focal mechanism (beach ball). Colored triangles stand for seismic stations used in the EGF procedure. Black triangles show the extended set of stations used in the radiated energy estimate. Inset shows the study area (red box) as well as the epicenter of the earthquake (red star). Single-station STFs obtained from the EGF procedure on P wave (B) and S wave (C). STFs are sorted as a function of station azimuth from the fault strike. Waveform colors correspond to those of the stations in (A). The gray dashed lines are the predicted widths of the P- and S-STFs (see main text).

  • Fig. 2 Rupture directivity and velocity estimate.

    (A) Contours of normalized variance reduction as a function of rupture velocity VR and percent unilateral rupture values e. The variance of the best-fit model in this plot is set to 1. Dark blue contours indicate variability within 10%, and the dashed line shows the best-fit rupture velocity. (B) Stacked P- and S-STFs resulting from the correction using our best-fit rupture velocity VR = 1.3 km/s. (C) Single-station S-STFs corrected for directivity effects using the stretching method with VR = 1.3 km/s. (D) Same as (C), with VR = 3.8 km/s. Red waveform at the bottom of each figure is the stack of all the corrected STFs. This correction involves stretching the STFs at station i with a factor of 1/Di.

  • Fig. 3 Temperature modeling of the Wyoming earthquake.

    (A) The VS model (25) in the western United States at a depth of 75 km and east-west cross sections showing the location of the Wyoming earthquake (star) in the strong velocity gradient. (B). Geothermal models (left; inset shows a zoom around the hypocenter) and predicted shear wave velocities using the approach of Faul and Jackson (24) that best fit the VS tomography models (right) of Schaeffer and Lebedev (26) (blue area) and Shen et al. (25) (red area). The geothermal models assume a crustal thickness of 50 km and produce surface heat flows between 40 and 60 mW m−2. The range of temperatures at the hypocentral depth predicted is from 750° to 850°C in the upper range of the brittle-ductile transition.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Temperature modeling for the Randolph, UT earthquake.
    • fig. S2. Comparison of estimated S wave corner frequencies and the best-fitting source model obtained from the STF stretching approach.

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