- Ground-motion model is:
where PGA is in gal, C

_{0}= 0.192, C_{1}= 0.867, C_{2}= -0.294, C_{3}= -0.008, C_{4}= 0.113 and σ = 0.903. - Use 2 site classes:
- Rock
- Class 1 (rock and hard alluvial with V
_{s,30}> 800m∕s) and class 2 (thin soft alluvial with 500 ≤ V_{s,30}≤ 700m). S = 0. - Soil
- Class 3 (soft gravel and sandy sites with 300 ≤ V
_{s,30}leq500m∕s) and class 4 (soft soil with V_{s,30}< 300m∕s). S = 1.

- Use data of Zaré and Bard (2002).
- Select records with PGA of any component > 0.05m∕s2.
- Choose functional form because it is simple and hence avoids computational difficulties.
- Use r
_{epi}rather than r_{hypo}because of uncertainties in focal depth estimates and because almost all earthquakes have depths ≤ 35km. - Originally use coefficients for each of the 4 site classes of Zaré and Bard (2002) but find that the order of predicted PGAs is not as expected (e.g. PGAs on site class 4 are smaller than those on site class 2). Therefore, combine the original classes 1 and 2 together and classes 3 and 4 together.
- Plot residuals w.r.t. predicted PGA and find no trend.