- Ground-motion model is (their model D): where GM is in g, θ1 = 4.31964, θ2 = -0.00175, θ3 = -2.40199, θ4 = 0.19029, θ5 = 2.14088, θ6 = 0.09754,
θ7 = -0.21015, θ8 = 0.38884, θ9 = -2.29732, θ10 = 448.88360, σ = 0.5099 (intra-event) and τ = 0.4083
(inter-event) for horizontal PGA using the static dataset without the Chi-Chi data and θ1 = 1.50813,
θ2 = 0.15024, θ3 = -2.52562, θ4 = 0.17143, θ5 = 2.12429, θ6 = 0.10517, θ7 = -0.16655, θ8 = 0.22243,
θ9 = -0.11214, θ10 = 19.85830, σ = 0.5141 (intra-event) and τ = 0.4546 (inter-event) for vertical PGA
using the static dataset without the Chi-Chi data. Coefficients are also given for the three other models
and for both the dynamic and the static datasets but are not reported here due to lack of space.
- Use two site categories:
S = 0
- Soil: includes sites located on deep broad and deep narrow soil deposits.
S = 1
- Rock: includes sites that are located on shallow stiff soil deposits;
- Use three rupture mechanism categories:
F = 0
- Strike-slip, 39 earthquakes, 387 records;
F = 0.5
- Reverse/oblique, 13 earthquakes, 194 records;
F = 1
- Thrust, 16 earthquakes, 412 records.
- Process records using two procedures as described below.
- Use the standard PEER procedure with individually chosen filter cut-offs.
- Fit the original integrated velocity time-history with three different functional forms (linear in velocity;
bilinear, piecewise continuous function; and quadratic in velocity). Choose the ‘best-fit’ result and
view it for reasonableness. Differentiate the velocity time-history and then low-pass filter with a causal
Butterworth filter with cut-offs about 50Hz.
- PGA values from the two processing techniques are very similar.
- Investigate using a nonlinear model for site response term but the resulting models did not improve the
- Also try three other functional forms: which all give similar standard deviations and predictions but prefer model D.
- Models oversaturate slightly for large magnitudes at close distances. Therefore recommend that the PGA
equations are not used because this oversaturation is based on very little data.
- Because the Chi-Chi short period ground motions may be anomalous relative to California they develop
equations including and excluding the Chi-Chi data, which only affects predictions for large magnitudes
(M > 7.5).