- Ground-motion model is:
- Response parameter is pseudo-velocity for 5% damping.
- All data from rock sites.
- Includes only if a reliable seismic moment estimate exists.
- Converts ECTN vertical seismograms to equivalent horizontal component by multiplying by 1.4.
- Includes Nahanni (western Canada) earthquakes because exhibit dominant characteristics of eastern North
American shocks (low seismicity area, high horizontal compressive stress, thrust mechanisms dominant,
no surface ruptures despite shallow focus and rocks have high seismic velocity).
- Excludes US digital strong-motion Saguenay records due to low resolution. Two effects on response spectra:
i) high frequencies contaminated by a ‘mathematical noise’ floor, ii) significant errors in amplitudes of low
to intermediate frequencies (severity dependent on resolution degree). Inclusion of such data could lead to
significant misinterpretation of these earthquakes.
- Most records (66, 65%) from R ≥ 111km and M ≤ 5.22.
- Examines residuals from equations. Finds no persistent trends except for Saguenay data (M = 6) between
63 ≤ R ≤ 158km.
- Notes data very limited in large magnitude range and that one or two earthquakes are controlling
- Notes different regression technique could change predictions for large magnitudes but i) data too limited
to warrant more sophisticated analysis and ii) may be other factors, in addition to number of recordings,
which should be considered in weighting each earthquake.