- Ground-motion model is:
where y is in cm∕s2, C0 = 4.75, C1 = 0.52, C2 = -1.00 and σ = 0.53 for hard ground and horizontal;
C0 = 3.77, C1 = 0.70, C2 = -1.24 and σ = 0.64 for hard ground and vertical; C0 = 4.37, C1 = 0.57,
C2 = -0.91 and σ = 0.52 for medium ground and horizontal; C0 = 3.20, C1 = 0.75, C2 = -1.07 and
σ = 0.55 for medium ground and vertical; C0 = 4.68, C1 = 0.55, C2 = -0.99 and σ = 0.54 for soft ground
and horizontal; and C0 = 3.53, C1 = 0.71, C2 = -1.10 and σ = 0.66 for soft ground and vertical.
- Use 3 site classes (and develop independent models for each):
- Equivalent to rock. 57 records.
- Soil depth < 20m or ‘shallow’. Includes sites described as ‘medium’.53 records.
- Soil depth > 20m or ‘deep’. Includes sites described as ‘soft’ or ‘alluvium’. 53 records.
Notes that difficult to classify due to lack of information for some stations (particularly for soft and medium
- Extends models of PML (1982, 1985) to spectral ordinates.
- Develop for use in the UK.
- Use earthquakes with focal depths ≤ 30km.
- Prioritize data away from well-defined plate-boundaries, e.g. central and eastern North America
(Miramichi, Nahanni, New Madrid), mainland China (e.g. Tangshan) and the Alpide Belt (Ancona,
Friuli, Irpinia, Cephalonia, Koyna, Montenegro, Imotski, Gazli, Tabas), over data from California. When
Californian data is required use near-field records so that model not affected by specific attenuation of
California. California data was required for soft ground model because of lack of near-field data from other
- Vast majority of data from Mw4 to 7 and from ≤ 100km.
- Because of limited information on stress field and diversity of focal mechanisms in the UK do not consider
style of faulting when selecting data.
- Correct data for instrument response and apply elliptic filter for majority of data (some data already
processed using similar schemes). Note that differences below 0.04s between records corrected in different
ways are minor.
- Use PGAs from processed data, which note may be slightly lower than those from uncorrected records.