- Ground-motion model is: where PGA is in g, b0 = -1.2780 ± 0.1909, b1 = 0.2853 ± 0.0316, b2 = -1.730 × 10-3 ± 2.132 × 10-4 and
σ = 0.3368 (± indicates the standard deviation of the coefficients). h was fixed arbitrarily to 8km.
- Use data from ISESD (Ambraseys et al., 2004). Select using de < 1000km, 5 ≤ M ≤ 7 (where M is either
Mw or Ms).
- Focal depths < 20km.
- Only use data from strike-slip earthquakes.
- Note that coefficient of variation for b coefficients is in range 11 to 15%.
- Note that b0 and b1 are very strongly negatively correlated (correlation coefficient of -0.9938), believed to
be because PGA is governed by b0 + b1M as D approaches zero, but they are almost uncorrelated with b2
(correlation coefficients of -0.0679 and -0.0076 for b0 and b1 respectively), believed to be because of zero
correlation between M and D in the data used.
- Also derive equation using log 10(PGA) = b0 + b1M + b2R + b3 log 10(R) (do not report coefficients) and
find slightly smaller residuals but similar behaviour of the b parameters.
- Plot distribution of residuals (binned into intervals of 0.25 units) and the normal probability density