The format follows that used by Herrmann in his 2011 Seismological Society of America presentation in Memphis.
All available broadband data are reduced to ground velocity (m/s) and narrow band pass filtered at center frequencies, fc, of 0.25, 1.0, 3.0 and 8.0 Hz. Defining corners fL=fc/1.414 and fH=1.414 fc , the filter consisted of an 8-pole highpass Butterworth filter and an 8-pole lowpass Butterworth filter, implemented using the gsac command
hp c ${FL} n 8 lp c ${FH} n 8The peak filtered velocity is then saved for the plots.
The observed values are then compared to the predictions of the Atkinson Boore (1995), Frankel (1996) and the Atkinson (2004) models for eastern North America. I used the random vibration theory program rvcal which consists of a wrapper to provide input to David Boore's smsim program. The program is run using the command line:
rvcal -V -B -MODEL ${MOD}.mod -MW ${MW} -FN ${FREQ} -R ${DIST} -OA -DT 0.01where the SHELL parameter MOD is the propagation/source model file, MW is the moment magnitude, FREQ is the filter frequency, DIST is the desired distance. The -B and -V flags indicate that the peak filtered velocity is desired.
Plots are made for each of the 3-components of ground motion, vertical (Z), radial (R) and transverse (T):
Propagation models
Source code
gfortran rvcal.f -o rvcalFor the command
rvcal -V -B -MODEL F96.txt -MW 5.7 -FN 0.25 -R 100 -OA -DT 0.01The output is
100.000 5.700 0.126E-02 vmax 0.25 0.05 T 0.711E-03 0.191E-02 0.29With annotation the output is
Dist(km) Mw Peak(m/s) Peak Freq Damp Butter Max05 Max95 Freq20 100.000 5.700 0.126E-02 vmax 0.25 0.05 T 0.711E-03 0.191E-02 0.29where Damp is a place holder and has no meaning for a Butterworth filter, Max05 and Max95 are the 5% and 95% bounds on the peak value and Freq20 is the frequency of zero crossings.