- Ground-motion model is: where Y is in g, a1 = -0.3299, a2 = -0.3114, a3 = -0.3320, b1 = 0.3498, b2 = -0.0294, c1 = -2.7994,
c2 = 0.2734, c3 = -0.0005, d1 = -0.3827, ϕ = 0.37 (intra-event), τu = 0.21 (inter-event unspecified
mechanism), τS = 0.21 (inter-event specified mechanism), σu = 0.43 (total unspecified mechanism) and
σS = 0.43 (total specified mechanism). Fix h = 10km because insufficient data.
- Use V s,30 to characterise sites. Most sites have only estimated V s,30.
- Class earthquakes into 3 mechanisms:
- RR = 1, U = SS = 0.
- Includes 1 normal earthquake. SS = 1, U = RR = 0.
- Earthquakes that did not have a reported mechanism. U = 1, RR = SS = 0.
- Use data from: NGA-East flatfile, 1976 Mw6.8 Gazli, 1985 Mw6.9 Nahanni, 2001 Mw7.6 Bhuj and
macroseismic intensities converted into ground motions from 1811-1812 Mw7.5, 7.3 and 7.7 New Madrid,
1886 Mw7.0 Charleston, 1925 Mw6.2 Charlevoix and 1929 Mw7.2 Grand Banks earthquakes (Mw > 6).
Exclude data from higher attenuating areas of the Gulf Coast and western North America, i.e. west of
100W or south of 35N.
- Use only a single term for geometric spreading due to limited data at < 50km.
- 13 records from Bhuj event only for PGA and 0.4, 0.75, 1.0 and 1.25s.
- Vast majority of data from Mw < 6 and repi > 50km.
- Compare predictions at Mw5.9 and observations for three events with magnitudes close to Mw5.9. Also
compare predictinos and observations at Mw7.6. Repeat regressions without the intensity-derived data.
Find small effect for Mw5.9 because large number of records for smaller magnitudes but a large impact at