• Analysis of regional seismograms and 3D synthetic seismograms for the 2016-01-24 Mw 7.1 Iniskin earthquake in southern Alaska

      Tape, Carl (2016-11-03)
      I perform two analyses to identify cases of seismogram clipping or other problems (e.g., data gaps) for the 2016-01-24 Mw 7.1 Iniskin, Alaska, earthquake. The first analysis is a comparison of synthetic and observed seismograms: three-component, displacement seismograms filtered between periods 4-80 s. The subset of 141 stations is limited to an oblique rectangular region that is 1200 km x 600 km (Figures 1 and 2) and used in a seismic wavefield simulation with a three-dimensional seismic velocity model. I identify 60 out of 141 stations that are suspected of clipping or other problems. Of the 81 good stations, only 8 are within 250 km of the Iniskin epicenter, and all 8 stations are outside of Cook Inlet basin, which strongly amplifies ground motion (both in data and in synthetics). The second, much simpler, analysis is to identify clipping based on the maximum counts on the waveforms. The max-counts approach reveals general agreeement with the classification based on long-period data and synthetics. The analysis suggests that (1) some recorded waveforms that exceed clipping levels may still be usable for some modeling purposes, and (2) some recorded waveforms that appear to be suitable for modeling purposes should probably be discarded due to clipping at high frequencies. The identification of suspected stations, along with the waveform comparisons, may help network operators assess the possibility of unexpected performance during the Mw 7.1 slab earthquake.
    • Assessment of station metadata in Alaska based on analysis of Love waves from the 2012-04-11 Mw 8.6 offshore Sumatra earthquake

      Tape, Carl (2012-07-05)
      This report is part of a detailed investigation of a Mw 3.9 earthquake near Nenana, Alaska, that was triggered by Love waves from a Mw 8.6 offshore Sumatra earthquake. Results from that study appeared in Tape et al. (2013). We analyze all BH and HH channel waveforms that are available at the Alaska Earthquake Center. This report has three objectives: (1) to provide information that may help improve station metadata at Alaska stations; (2) to provide a snapshot of station performance in Alaska at one particular time (11-April-2012); (3) to provide details and figures on part of the waveform processing used in Tape et al. (2013).
    • Curves Vhat_gamma(omega) (Tape and Tape, 2017) for download and details of their calculation

      Tape, Carl (2017-01-30)
      The files in this collection are a supplement to Tape and Tape (2017). Here we provide precomputed curves Vhat_gamma(omega), where Vhat_gamma(omega) is defined as in Section 2.4 of Tape and Tape (2017). The motivation for this work is the characterization of uncertainties for moment tensors for events in Earth's crust, such as earthquakes, volcanic events, and more. The curves Vhat_gamma(omega) were calculated using Matlab's integral2 function and have an accuracy of approximately 2 x 10^-7.
    • Seismic moment tensor catalog for Minto Flats fault zone (2000-2014)

      Silwal, Vipul (2015-12-07)
      We present moment tensor solutions for 15 earthquakes in the Minto Flats fault zone. Moment tensor solutions were generated using body waves and surface waves. The best solution was obtained through a grid-search in the double-couple moment tensor space using the "cut-and-paste" (CAP) approach of Zhu and Helmberger (1996). The files here are part of the PhD thesis work by Vipul Silwal. The materials were included as part of the supplement to Tape et al. (2015, BSSA).
    • Seismic moment tensor catalog for southern Alaska

      Silwal, Vipul (2015-09-23)
      The files here are part of the PhD thesis work by Vipul Silwal. This supplement will be cited in a manuscript to be submitted. A seismic moment tensor catalog of 106 events was generated using body waves and surface waves. The best solution (M0) was obtained through a grid-search in the double-couple moment tensor space (M) using the "cut-and-paste" (CAP) approach of Zhu and Helmberger (1996). The waveform fits for the 21 events in the Part I catalog is shown in Figure A, with the best-fitting depth plots in Figure B. The uncertainty analysis for these Part I events is shown in Figure C. The waveform fits for the other 85 events (Part II) is shown in Figure D; for these events the best depth search and uncertainty analysis was not performed.
    • Seismic moment tensor catalog for Uturuncu volcano, Bolivia

      Alvizuri, Celso (2015-12-07)
      We present seismic moment tensor solutions for 63 events at Uturuncu volcano, Bolivia. Moment tensor solutions were generated using body waves and surface waves. The best solution (M0) was obtained through a grid-search in moment tensor space using the "cut-and-paste" (CAP) approach of Zhu and Helmberger (1996) and Zhu and Ben-Zion (2013). The files here are part of the PhD thesis work by Celso Alvizuri