where Y is in cm∕s2, a = 0.73, b = -7.2 × 10-4, c1= 1.16, c2= 0.96, d = -1.48, e = -0.42 and σ = 0.31
for rock and a = 0.71, b = -2.38 × 10-3, c1= 1.72, c2= 0.96, d = -1.44, e = -2.45 × 10-2 and σ = 0.33
Use two site classes using southern California site classification map based on Vs,30 of Wills et al. (2000):
Class BC and above, Vs,30> 464m∕s. 35 SCSN stations with 958 records. 50 records from NGA.
Class C and below, Vs,30≤ 464m∕s. No data from very soft soils. 129 SCSN stations with 2630
records. 1557 records from NGA.
and develop independent equations for each since sufficient data.
Use data from the Southern California Seismic Network (SCSN) (150 stations) and COSMOS (6 events)
supplemented by the Next Generation Attenuation (NGA) dataset. Mainly used broadband data from
SCSN except when clipped, when accelerometric data is used instead.
Correct records for gain and baseline and convert to acceleration using differentiation, if needed.
For SCSN data use S-wave envelope amplitudes and not PGAs directly. Note that should be comparable
to true PGAs.
Constrain c2 to be approximately unity within regression.
Develop conversion factors for converting between different definitions of horizontal component and their
Compare predicted and observed PGAs for ranges: 6.5 < M < 7.5 (predictions for M7.0), 4.0 < M < 6.0
(predictions for M5.0) and M < 3.0 (predictions for M2.5) and find good match.
Examine residuals and find no significant trends w.r.t. distance or magnitude.
Compute station-specific site corrections for SCSN stations that recorded more than 3 times. Applying
these corrections for rock PGA produces a 20% reduction in σ (to 0.24).