- Ground-motion model is the same as for the associated horizontal model Campbell and Bozorgnia (2014)
(see Section 2.364) with the following coefficients: h4 = 1, c0 = -4.729, c1 = 0.984, c2 = 0.537,
c3 = -1.499, c4 = -0.443, c5 = -2.666, c6 = 0.214, c7 = 7.166, c8 = 0, c9 = -0.230, c10 = 0.759,
c11 = -0.356, c12 = 1.019, c13 = 0.373, c14 = -0.117, c15 = -0.097, c17 = 0.1020, c18 = 0.0442,
c19 = 0.00784, c20 = -0.0053, Δc20,JI = -0.0018, Δc20,CH = 0.0039, k1 = 865, a2 = 0.167, h1 = 0.241,
h2 = 1.474, h3 = -0.715, h5 = -0.337 and h6 = -0.270, c16 = 0.0 (no deep basin effects), k2 = 0.0 (no
soil nonlinearity), k3 = 0.0 (no deep basin effects) and c and n are not need because k2 = 0.
- Ground-motion model is (for aleatory variability): where τ1V = 0.461, τ2V = 0.347, ϕ1V = 0.694, ϕ2V = 0.493, σV = 0.833 for Mw ≤ 4.5 and σV = 0.603 for
Mw ≥ 5.5.
- Characterise sites using V s,30. Because vertical site response behaves linearly in most cases (even when
horizontal response may be strongly nonlinear) do not model soil nonlinearity. Do not think that this
affects the applicability of the model. Recommend model for V s,30 between 150 and 1500m∕s (for higher
V s,30 recommend setting V s,30 to 1500m∕s).
- Use 3 mechanisms:
- Reverse/reverse-oblique. Rake angle 30 < λ < 150∘. FRV = 1, FNM = 0.
- Normal/Normal-oblique. Rake angle -150 < λ < -30∘. FNM = 1, FRV = 0.
- Strike-slip. Other rake angles. FRV = FNM = 0.
Use 2 regions:
- SJ = 1
- SJ = 0
- Do not include deep basin terms in model because modelling is inconclusive and little evidence from data
that basin effects are important for vertical motions.
- Recommend model for depth to top of rupture ZTOR between 0 and 20km, hypocentral depths between 0
and 20km and fault dips δ between 15 and 90∘.
- Vertical-component NGA-West 2 model corresponding to horizontal model of Campbell and
Bozorgnia (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. Use same data selection criteria as Campbell and
Bozorgnia (2014) but exclude: records without vertical components, those that triggered on horizontal
motion or are of questionable quality. Exclude aftershocks (class 2 events) within immediate vicinity of
inferred mainshock fault rupture plane.
- 6989 near-source (rrup ≤ 80km) records from 282 events. Use these with
2-stage maximum-likelihood regression to derive near-source model. Use far-source database (80–500km)
to develop regionally-dependent anelastic attenuation terms. Apply limited smoothing to coefficients.
- From regression fmag predicted oversaturation for PGA and short-period PSA at large Mw and short
rrup. Decide to constrain fmag to be constant at Mw > 6.5 and rrup = 0 when regression indicates
oversaturation. Find c1, c2 and c3 were not significantly different to those from horizontal model and hence
fix them to the horizontal coefficients in final regression.
- Plot inter- and intra-event residuals (individual and binned into small intervals) w.r.t. different variables.
Find no significant biases or trends.