- Ground-motion model is:
where PGA is in gal, a1 = 2.18, a2 = 0.0218, a3 = 33.3, a4 = 7.8427, a5 = 18.9282 and σ = 86.4.
- Use three site categories:
SA = 0, SB = 0
- Rock, 55 records.
SA = 1, SB = 0
- Soil, 94 records.
SA = 0, SB = 1
- Soft soil, 72 records.
Classify by adopting those given by other authors, selecting the class reported by more than one source.
- Most data from instruments in small buildings.
- Use records with PGA > 20gal to avoid bias due to triggering.
- PGAs of records between 20 and 806gal.
- Use records from earthquakes with Mw ≥ 4 because smaller earthquakes are generally not of engineering
- Derive linear conversion formulae (correlation coefficients > 0.9) to transform Ms (39), mb (18), Md (10)
and ML (6) to Mw (73 events in total).
- Note that rupture surfaces have not been accurately defined for most events therefore use repi.
- Note that accurate focal depths are often difficult to obtain and different data sources provide different
estimates therefore do not use rhypo.
- Use records from ≥ 5km because of assumed average error in epicentral locations.
- Use records from ≤ 100km because this is the distance range where engineering significant ground motions
- Most data from Mw ≤ 6 and de ≤ 50km.
- Do not consider faulting mechanism because focal mechanism solutions for most earthquakes not available.
- Plot observed versus predicted PGA and find that a few points fall above and below the lines with slopes
1 : 0.5 and 1 : 2 but most are between these lines.
- Note that to improve precision of equation site characterisation based on V s measurements should be
included. Also note that directivity, fault type and hanging wall effects should be considered when sufficient
data is available.