- Ground-motion model is: where A is in m∕s2, c1 = -1.471, c2 = 0.849, c4 = -0.00418 and σ = 0.83.
- Use records from rock sites (presumably with hard rock or firm ground conditions).
- Assume intraplate refers to area that are tectonically stable and geologically more uniform than plate
boundary areas. Select records from several ‘reasonably’ intraplate areas (eastern N. America, China,
Australia, and some parts of Europe), due to lack of data.
- Select records which are available unprocessed and with sufficient information on natural frequency and
damping of instrument.
- Use Ms, when available, because reasonably unbiased with respect to source dimensions and there is
globally consistent calculation method.
- Most (72%) records from earthquakes with M ≤ 5.5. Tangshan and Friuli sequence comprise a large subset.
Correlation coefficient between magnitude and distance is 0.31.
- Instrument correct records and elliptical filter with pass band 0.25 to 25.0Hz.
- If depth unknown assume 15km.
- Choose R0 = 100km although depends on crustal structure and focal depth. It is distance at which spherical
spreading for S waves overtaken by cylindrical spreading for Lg waves.
- PGA attenuation relation is pseudo-acceleration equation for 0.025s period and 5% damping.
- Plot residuals against magnitude and distance.
- Note ‘first order’ results, because data from several geological regions and use limited data base.