- Ground-motion model is:
_{1}= 2,154,000, c_{2}= 2.10, d_{1}= 0.046, d_{2}= 0.445, e_{1}= 2.515, e_{2}= -0.486, for y = 0.01g σ = 0.5, for y = 0.05g σ = 0.48, for y = 0.10g σ = 0.46 and for y = 0.15g σ = 0.41 (in terms of natural logarithm).Use 25 because assume energy centre of Californian earthquakes to be at depth 5km.

- Consider two site conditions but do not model:
- 1.
- Rock: (21 records)
- 2.
- Stiff soil: (38 records)

- 32% of records from San Fernando (9/2/1971) but verifies that relationship is not significantly biased by this data.
- Most records within 50km and most from earthquakes with magnitudes of about 6.5.
- Recognises that magnitude and distance are not independent variables.
- Find b
_{1}, b_{2}and b_{3}by dividing data according to distance and computing b parameters for each set using least squares. Find a distinct trend with little scatter.