- Ground-motion model is for combined model using both surface and borehole
(same as Boore and Atkinson (2008)): where μmedA is in g, Mref = 4.5, Rref = 1km, V ref = 760m∕s, href = 60m and Vsholeref = 3000m∕s
(reference values); c1 = -1.2534, c2 = 0.4271, c3 = -0.0140, e1 = -0.0663, e5 = -0.5997, e6 = -0.5012,
e7 = 0, blin = -0.4665, bh800 = -0.1801, a100 = -1.4372, a200 = -1.6518, b100 = -0.0269, b200 =
-0.1884, c100 = -0.2666, c200 = -0.3793, ϕ = 0.6293 (intra-event) for Mw < 5, ϕ = 0.6202 (intra-event)
for Mw > 6.5, τ = 0.4929 (inter-event) for Mw < 5, τ = 0.9164 (inter-event) for Mw > 6.5 (linear
interpolation of ϕ and τ between Mw5 and 6.5) and τ* = 0.4981 for Mw > 6.5 (computed using inter-event
residuals corrected for the observed bias using a linear term) .
- Characterise sites by V s,30, depth to reach V s of 800m∕s (h800) and V s at bedrock (Vshole).
- Uses an NGA functional form to reflect state of the art in ground-motion prediction and the form of Boore
and Atkinson (2008) specifically because it can be constrained by the data.
- Extension of analysis by Rodriguez-Marek and Montalva (2010) (see Section 4.201).
- Analysis conducted to investigate single-site variability of ground motions.
- Data from KiK-net on surface and at depth as processed by Pousse et al. (2005) and Cotton et al. (2008)
(see Sections 4.131 and 2.294 for details). Note that although Cotton et al. (2008) state that spectral
accelerations up to 3s can be used, in fact some spectral accelerations at long periods are less than the
number of decimals used for storing the data. Hence limit analysis to periods < 1.3s.
- Majority of data is for Mw ≤ 6.1, which will have an impact on the regression.
- Presents histogram of V s,30 at surface stations: peak around 500m∕s with very few records for V s,30 >
- Presents histogram of borehole depths: almost all at 100 and 200m. Use flag to indicate borehole instrument
depth ≤ 150m or > 150m.
- Presents histogram of V s,30 at borehole stations: roughly uniformly distributed between 1000m∕s and
2500m∕s with some higher and lower.
- Notes that geographical distribution of earthquakes shows clusters that could enable a further separation
of source and path effects from site effects in future studies.
- Only uses data from earthquake that were recorded by ≥ 5 stations to adequately constrain inter-event
- Uses multiple step regression method. First, uses only data from earthquakes recorded by > 100 stations
to constrain c3 and h by maximum-likelihood regression (after fixing c1 to a value between -0.2 and -1.1
and fixing c2 to 0). Next finds Mh and e7. Originally find that e7 is negative (oversaturation) but note
that lack of data from large earthquakes so constrain it to be positive. Mh is chosen by inspection. Rest
of coefficients found by random-effects regression.
- Combined model assumes source and path terms are independent of near-surface layering, which note is
desired from a phenomenological view.
- Plots inter-event residuals against Mw and find overestimation for Mw > 6.5 due to constraint that ground
motions do not oversaturate. Plots inter-event residuals against depth and find that motions from deeper
events underestimated, which relate to less attenuation than shallower events and possibly different stress
drops in shallow and deep earthquakes.
- Plots intra-event residuals against Mw and rrup and site parameters and find no trends. However, finds
trend in residuals from earthquakes recorded at rrup < 20km, which relate to lack of near-fault-effects and
nonlinear soil terms. Also finds decreasing variation in the intra-event residuals for rrup > 200km.
- Examines correlation between normalised inter- and intra-event residuals and concludes that they are
- Finds combined, surface and borehole inter-event residuals well correlated.
- Recommends use of combined model rather than the surface or borehole only models.
- Computes single-station residuals and σs, by defining site terms for each station based on intra-event
residuals, from 131 stations that recorded > 10 earthquakes. Finds slight magnitude dependence of
residuals. Finds no correlation between intra-event residuals corrected by site terms and inter-event
residuals. Examine in detail single-station residuals, associated σs and their various components w.r.t. to
their use in PSHA without the ergodic assumption. Report these single-station σs: surface ϕ = 0.4967,
borehole ϕ = 0.5060, surface σ = 0.6725 and borehole σ = 0.6684.
- Examine effect of selecting data from a station-to-event azimuthal bracket of 8∘ and finds that sigma is