- Ground-motion model is: where y is in g, coefficients c0 to c4, h and σ are from Joyner and Boore (1981) and c6 and V 0 are not
significant at 90% level so do not report them.
- Use data of Joyner and Boore (1981).
- Continuous site classification for soil sites in terms of shear-wave velocity, V , to depth of one quarter
wavelength of waves of period of concern. V measured down to depths of at least 30m and then extrapolated
using geological data. V known for 33 stations.
- Soil amplification factor based on energy conservation along ray tubes, which is a body wave argument
and may not hold for long periods for which surface waves could be important. Does not predict resonance
- Regress residuals, Rij, w.r.t. motion predicted for rock sites on log Rij = Pi + c6V j, where j corresponds
to jth station and i to ith earthquake. Decouples site effects variation from earthquake-to-earthquake
variation. Find unique intercept by requiring average site effect term calculated using shear-wave velocity
to be same as that calculated using rock/soil classification.
- No significant, at 90%, correlation between residuals and V for PGA.
- Repeat regression on residuals using V and depth to underlying rock (defined as either shear-wave velocity
> 750m∕s or > 1500m∕s). Find no correlation.