Soil characteristics known to bedrock for 571 (out of 1013) stations. Classify stations using NEHRP classification
using Vs,30 or converted N-values:
Vs,30> 1500m∕s, 0 stations
760 < Vs,30≤ 1500m∕s, 0 stations
460 < Vs,30≤ 760m∕s, 174 stations
360 < Vs,30≤ 460m∕s, 193 stations
250 < Vs,30≤ 360m∕s, 300 stations
180 < Vs,30≤ 250m∕s, 230 stations
Vs,30≤ 180m∕s, 116 stations
Define nonlinear (based on PGA at bedrock) soil amplification model using nonlinear analyses of sampled
soil conditions for each class of soils. Use this model to convert observed ground motion to motion at a C1
Response parameter is acceleration for 5% damping.
Focal depths, D, between 3 and 122km.
Distribution with respective to earthquake type (based on mechanism, location and depth) is: crustal
(3 ≤ D ≲ 25km), 13; interplate (10 ≲ D ≲ 70km), 23; and intraplate, 16 (30 ≲ D ≤ 122km).
PGA from 2 to 1114cm∕s2.
Try including different constant terms to model effect of earthquake type but find lower statistical
confidences of results. Therefore remove these coefficients. Believe that modelling of focal-depth dependency
may already include effect of earthquake type due to high correlation between depth and type.
Fit fourth-degree polynomials (in log(T)) through derived coefficients to generate smooth spectra.
Compare inter- and intra-event residuals to normal distribution using Kolmogorov-Smirnov test and find
that the intra-event residuals have a normal distribution and that the inter-event residuals almost have.
Examine magnitude-dependence of the standard deviations using residuals binned within different
magnitude ranges (Mw< 6.0, 6.0 ≤ Mw< 6.5, 6.5 ≤ Mw< 7.0 and Mw≥ 7.0) and do not find a clear
trend for either inter- or intra-event residuals.
Examine distance-dependence of the intra-event standard deviations and find that for some periods the
standard deviations show some depth-dependence for short and long distances.
Examine amplitude-dependence of the intra-event standard deviations and find some positive dependence
(σ increases for higher amplitude motions) for T ≤ 0.4s. Note that this may be due to a lack of small
amplitude motions due to nontriggering of instruments.