- Ground-motion model is:
- Use three site categories:
- Firm to hard rock: granite, igneous rocks, sandstones and shales with close to widely spaced fractures,
750 ≤ V s,30 ≤ 1400m∕s ⇒ SB = 0, SC = 0.
- Gravelly soils and soft to firm rocks: soft igneous rocks, sandstones and shales, gravels and soils with
> 20% gravel, 360 ≤ V s,30 ≤ 750m∕s ⇒ SB = 1 , SC = 0.
- Stiff clays and sandy soils: loose to very dense sands, silt loams and sandy clays, and medium stiff to
hard clay and silty clays (N > 5blows∕ft), 180 ≤ V s,30 ≤ 360m∕s ⇒ SB = 0, SC = 1.
- For shallow (fault rupture within 20km of earth surface) crustal earthquakes.
- Use free-field records. Records not significantly contaminated by structural feedback, excludes records from
structures with >2 stories.
- Chooses Ground-motion model because of simplicity. Note that other possible forms of equation may
have significant effect on results, but including more terms complicates relationships without reducing
- Do not give coefficients only predictions.