- Ground-motion model is:
where Y is in cm∕s2, a1 = 0.97412, a2 = 0.0074138, a3 = -0.0044524 and a4 = 2.1041 for mean horizontal;
a1 = 0.95461, a2 = 0.0073811, a3 = -0.0045837 and a4 = 2.4935 for vectorially-resolved component
including vertical; a1 = 0.96387, a2 = 0.006973, a3 = -0.00466 and a4 = 2.3969 for vectorially-resolved
component using two horizontal components; and a1 = 0.98212, a2 = 0.0073442, a3 = -0.0044279 and
a4 = 1.7006 for vertical; a5 = 0.0261 and a6 = 0.9594 for all. σ = 0.70.
- Data from 36 rock sites, which recorded between 1 and 23 events.
- All events recorded by ≥ 10 stations so that number of events and stations are comparable.
- Only use earthquakes with Global CMT Mw available.
- Focal depths, Z, between 5 and 69km with most ≤ 25km.
- Try a different function for the distance decay (-ln) and find that fits the data
almost equally well. Prefer the selected form because it has been used for Japanese models using more
- Correlation between parameters is: between M and R 0.49, between M and Z 0.21 and between Z and R
- Fit distance decay term of form -ln(R+c) to each earthquake individually. Find a5 and a6 from plot of c
against M. Choose a5 and a6 that can be used for all across periods. Next find coefficients a1 to a4 based
on data adjusted by distance decay term.
- Find no trends in residuals w.r.t. M, Z or R.
- Plot observations against predictions for magnitude-unit wide intervals and find good fit.
- Note that model is not definitive because many other data available. Believe model is adequate for
illustration of how a model can be improved by event, site and path terms.