- Ground-motion model is:
- Use 3 site classes:
- Soil soil. s = 0
- Stiff soil. s = 1
- Rock or very dense soil. s = 2
- Response parameter is pseudo-velocity for 5% damping.
- Derive model for comparison with conditional scaling model for prediction of PSV in aftershocks given
PSV in mainshock.
- Use data from 1999 Chi-Chi earthquake (M7.3, h = 10.33km, 93 records) and its 15 largest aftershocks
(4.99 ≤ M ≤ 6.80, between 3 and 51 records per event, 405 records in total). Records from 93 stations,
which did not contribute equal numbers of records. Select records with repi ≤ 50km since aftershock
motions are very weak at larger distances. Did not use data from stations that did not trigger in mainshock.
- Focal depths 1.0 ≤ h ≤ 16.8km.
- Exclude data from 11 records for T > 5s because of noise in PSV spectra.
- Original include a2(T)M2 and a3(T)D terms but these are removed because a2(T) and a3(T) are positive,
which is unphysical. Conclude insufficient data to constrain these coefficients.
- Compare coefficients and σs from conditional and unconditional models and conclude that can roughly
obtain conditional model from unconditional one.
- Do not report coefficients.