- Ground-motion model is [based on Abrahamson et al. (2013, 2014)] (for median): where: Sa is in g, Dip is fault dip in degrees, W is down-dip rupture width, V Lin = 660, c4 = 8.6,
a1 = 1.350, a2 = -1.087, a3 = 0.275, a4 = 0.121, a5 = -0.592, a6 = 1.780, a8 = 0.0, a10 = -0.397,
a11 = -0.200, a12 = -0.120, a13 = 0.670, a14 = -0.168, a15 = 1.100, a17 = -0.0062, a25 = 0.0015,
a26 = -0.0007, a27 = 0.0031, a28 = 0.0035, a29 = -0.0010, a31 = 0.252 and a35 = 0.380.
- Ground-motion model is (for aleatory variability): where: s1 = 0.734 and s2,all = 0.520, s3 = 0.440, s4 = 0.350, s2,NoJP = 0.450 and s4,NoJP = 0.322.
- Use 3 faulting mechanisms:
- Other rake angles. 221 events. FRV = FN = 0.
- Rake angles between 30 and 150∘. 79 events. FRV = 1, FN = 0.
- Rake angles between -30 and -150∘. 26 events, mostly 4.6 ≤ Mw ≤ 6. FN = 1, FRV = 0.
Use two earthquake types:
- Mainshocks. FAS = 0.
- Aftershocks. Events with centroid rjb < 15km (CRjb). FAS = 1.
Use two locations w.r.t. vertical projection of the top of rupture:
- FHW = 1.
- FHW = 0.
Use five regional terms to adjust model w.r.t. base model (all other regions, dominated by California):
- FTW = 1
- FCN = 1
- FJP = 1
- FME = 1
- FIT = 1
- Vertical-component NGA-West 2 model corresponding to horizontal model of Abrahamson
et al. (2013, 2014) (see Section 2.364 for details of data and approach used to develop model). Use similar
database and functional form but aspects are different.
- Functional form does not include terms for nonlinear site amplification or soil depth used by Abrahamson
et al. (2013, 2014). Simulations of nonlinear site amplification not consistent with data. Notes that
reduced confidence in using the model away from an average site with V s,30 = 450m∕s because of lack of
- Use same database as Abrahamson et al. (2013, 2014) but remove records without vertical component
(55 records) and those for which vertical component is questionable (98 records).
- Regress in a number of steps following approach of Abrahamson et al. (2013, 2014).
- Smooth coefficients to assure smooth spectra and to make model extrapolate in reasonable manner.
- Find ϕ from Japanese data much higher than from Californian or Taiwanese data, which relate to shallower
soils in Japan. Recommend s2,NoJP and s4,NoJP for use outside Japan.
- Note that V s,30 scaling for Japanese sites is distance dependent but V s,30 slope in model is distance
independent. Use V s,30 slope from rrup ≤ 50km for model because most relevant for applications. Note
that at larger distance may be a misfit between predictions of regional model and observations from Japan.
- Examine inter-event residuals w.r.t. Mw and separated by region. Find no trends.
- Examine intra-event residuals w.r.t. V s,30, Sa1180 (predicted spectral acceleration for V s,30 = 1180m∕s)
and Z1 (depth to V s,30 = 1km∕s horizon). Find no trends.