Appendix C

Fourier Spectra

Appendix C contains Fourier acceleration spectra from selected aftershocks. First, spectra from all seismograms recorded during the largest event - 0171333T - are shown. Second, for comparison of a range of aftershocks, spectra are shown from C9V seismograms for all earthquakes whose P-arrival triggered C9V. C9V was our best instrument in terms of number of triggers and proximity to the hypocenters.

Each seismogram was hi-pass filtered at 2 Hz prior to analysis (see Appendix B). Five seconds of each seismogram were analyzed and a cosine taper was applied to the first and last 10 percent prior to the FFT. Velocity spectra were multiplied by frequency to obtain acceleration. There was no correction for attenuation, instrument, or anti-alias filter. Scaling within each group of spectral plots is similar to facilitate comparison.

[ The Appendix figures are not available online ]

U.S. Geological Survey

Open-File Report 82-777

Local Multi-Station Digital Recordings of
Aftershocks of the January 9th, 1982
New Brunswick Earthquake