- Ground-motion model is: where DRS(T) is in cm∕s2, a1 = -1.18, a2 = 0.559, a3 = -1.624, a4 = 0.018, a5 = 0.445, aB = 0.25,
aC = 0.31, aD = 0.33, aN = -0.01, aR = 0.09, aS = -0.05, k1 = 2.03, k2 = -0.138, k3 = -0.962 and σ =
- Use four Eurocode 8 classes:
- Rock. SB = SC = SD = 0.
- Stiff soil. SB = 1, SC = SD = 0.
- Medium-dense soil deposits. SC = 1, SB = SD = 0.
- Soft soil deposits. SD = 1, SB = SC = 0.
- Use three faulting mechanisms:
- EN = 1, ER = ES = 0.
- ER = 1, EN = ES = 0.
- ES = 1, EN = ER = 0.
- Update of Cauzzi and Faccioli (2008) (see Section 2.290) using more data and rrup rather than rhypo
because this is more appropriate close to large earthquakes.
- Find that differences between rrup and rhypo are not statistically significant for Mw ≤ 5.7 so use rhypo
below this threshold.
- Most data from Japan.
- Use a subset of data to decide on the best functional form, including forms with Mw2 and/or
distance-saturation terms and site classes or V s,30 directly.
- Carefully examine (not show) fit between predicted and observed spectra in near-source region and find
distance-saturation term provides best fit.
- Note that Mw2 term has negligible impact on σ but improves predictions for large Mw. Drops Mw2 from
final functional form.
- Find site terms significantly reduce σ.
- Effect of style of faulting terms on σ is minimal but does improve predictions.
- Note that functional form means that one-step rather than two-step approach must be used that means
that effects of magnitude and distance cannot be decoupled and σs are larger.
- Compare predictions and observations for two records and find overprediction in one case and
underprediction in other, which relate to the approximation of the model and not an error in determination
- Test model against data (4.5 ≤ Mw ≤ 6.9, rrup < 150km) from the Italian Accelerometric Archive
(ITACA) using residual plots and method of Scherbaum et al. (2004). Find that good ranking is obtained
using approach of Scherbaum et al. (2004). Find trends in residual plots, which correct using functions,
with coefficients k1, k2 and k3, fit to the residuals. ki can be added to ai to obtain corrected coefficients
(a4 and a5 are unchanged).
- Note that improvements to Cauzzi and Faccioli (2008) are still ongoing.