### 2.65 Gaull (1988)

• Ground-motion model is:

where PGA is in ms2, 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:
1.
Rock: 6 records
2.
Alluvium: 5 records
3.
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.