- Ground-motion model is:
where PGA is in m∕s2, a1 = 5, a2 = 3, a3 = 20, a4 = 6, a5 = 0.77, a6 = 0.0045 and a7 = 1.2 (σ not given).
- Considers three site categories but does not model:
- Rock: 6 records
- Alluvium: 5 records
- Average site: 10 records
- Most records from earthquakes with magnitudes about 3 and most from distances below about 20km.
- Band pass filter records to get PGA associated with waves with periods between 0.1 and 0.5s because high
frequency PGA from uncorrected records not of engineering significance.
- Adds 4 near source (5 ≤ R ≤ 10km) records from US, Indian and New Zealand earthquakes with
magnitudes between 6.3 and 6.7 to supplement high magnitude range.
- Add some PGA points estimated from intensities associated with 14/10/1968 ML = 6.9 Meckering
earthquake in Western Australia.
- Plot 6 records from one well recorded event with ML = 4.5 and fit an attenuation curve of form
log PGA = b1 - b2 log R - b3R by eye. Plot PGA of all records with 2 ≤ R ≤ 20km against magnitude, fit
an equation by eye. Use these two curves to normalise all PGA values to ML = 4.5 and R = 5km from
which estimates attenuation relation.