- Update of Spudich et al. (1997) see Section 2.144.
- Ground-motion model is: where Z is in g, b1 = 0.299, b2 = 0.229, b3 = 0, b5 = -1.052, b6 = 0.112, h = 7.27 and σ =
where σ1 = 0.172, σ2 = 0.108 and for randomly oriented horizontal component σ3 = 0.094 and for larger
horizontal component σ3 = 0.
- Values of σ3 (used to compute standard deviation for a randomly orientated component) reported in
Spudich et al. (1999) are too large by a factor of .
- Use two site categories (could not use more or V s,30 because not enough data):
Γ = 0
- Rock: includes hard rock (12 records) (plutonic igneous rocks, lava flows, welded tuffs and
metamorphic rocks unless severely weathered when they are soft rock), soft rock (16 records) (all
sedimentary rocks unless there was some special characteristic noted in description, such as crystalline
limestone or massive cliff-forming sandstone when they are hard rock) and unknown rock (8 records).
36 records in total.
Γ = 1
- Soil (alluvium, sand, gravel, clay, silt, mud, fill or glacial outwash of more than 5m deep): included
shallow soil (8 records) (5 to 20m deep), deep soil (77 records) (> 20m deep) and unknown soil (21
records). 106 records in total.
- Applicable for extensional regimes, i.e. those regions where lithosphere is expanding areally. Significantly
different ground motion than non-extensional areas.
- Criteria for selection of records is: Mw ≥ 5.0, df ≤ 105km. Reject records from structures of more than
two storeys or from deeply embedded basements or those which triggered on S wave. Also reject those
close to dams which may be affected by dam. Also only use records already digitised.
- Include records from those instrument beyond cutoff distance, i.e. beyond first instrument which did not
trigger, because of limited records and lack of data on non-triggering.
- Not enough data to be able to find all coefficients so use b2 and b3 from Boore et al. (1993) and b6 from
Boore et al. (1994a).
- One-stage maximum likelihood method used because many events used which only have one record
associated with them and the two-stage method underestimates the earthquake-to-earthquake component
of variation in that case.
- Correction technique based on uniform correction and processing using upper, fh, and lower, fl, frequencies
for passband based on a visual inspection of Fourier amplitude spectrum and baseline fitting with a
polynomial of degree 5.
- Check to see whether normal and strike-slip earthquakes give significantly different ground motions. No