- Ground-motion model is:
where PGA is in gal, for type I sites a1 = 46.0, a2 = 0.208 and a3 = -0.686 , for type II sites a1 = 24.5,
a2 = 0.333 and a3 = -0.924, for type III sites a1 = 59.0, a2 = 0.261 and a3 = -0.886, for type IV sites
a1 = 12.8, a2 = 0.432, a3 = -1.125 and for all sites a1 = 34.1, a2 = 0.308 and a3 = -0.925 (σ not given).
- Use four site categories:
- Tertiary or older rock (defined as bedrock) or diluvium with depth to bedrock, H < 10m, 29 records.
- Diluvium with H ≥ 10m or alluvium with H < 10m, 74 records.
- Alluvium with H < 25m including soft layer (sand layer vulnerable to liquefaction or extremely soft
cohesive soil layer) with thickness < 5m, 130 records.
- Other than above, usually soft alluvium or reclaimed land, 68 records.
- Select earthquakes with Richter magnitude ≥ 5.0, hypocentral depth ≤ 60km and which include at least
one record with PGA ≥ 50gals (0.5m∕s2). Exclude records with PGA < 10gals (0.1m∕s2).
- All records for M ≥ 7.0 are from distance > 60km.
- Do regression separately for each soil category and also for combined data.