- Ground-motion model is:
where A is in cm∕s2, c1 = 7.969, c2 = 1.220, c3 = -1.131, c4 = 0.212, h = 10km (fixed after tests) and σ =
0.825 for horizontal PGA and c1 = 7.262, c2 = 1.214, c3 = -1.094,
c4 = 0.103, h = 10km (fixed after tests) and σ = 0.773 for vertical PGA.
- Uses four site categories (S equals number of site category):
- Rock. 117 records.
- Alluvial. 52 records.
- Gravel and sandy. 70 records.
- Soft. 39 records.
Does analysis combining 1 and 2 together in a firm rock category (S = 0) and 3 and 4 in a soft soil category
(S = 1) and for all site categories combined. Reports coefficients for these two tests.
- Focal depths between 9 and 73km. Most depths are shallow (depths fixed at 33km) and majority are about
10km. Does not use depth as independent parameter due to uncertainties in depths.
- Uses Mw because nearly all reported Ground-motion models use Mw.
- Uses macroseismic distance for three events since no repi reported.
- Believes that methods other than vectorial sum of both horizontal PGAs underestimates true PGA that
acts on the structure. Notes that vectorial sum ideally requires that PGAs on the two components arrive
at the same time but due to unknown or inaccurate timing the occurrence time cannot be used to compute
the resolved component.
- Does not consider faulting mechanism due to lack of information for many events.
- Most records from Mw ≤ 5.
- Originally includes terms c5(M - 6)2 and c6EPD but finds them statistically insignificant so drops them.
- Notes that all coefficients pass the t-test of significance but that the site coefficients are not highly
significant, which relates to poor site classification for some stations.
- Compares observed and predicted PGAs with respect to distance. Notes that match to observations is
- Compares observed PGAs during Bam 2003 earthquake to those predicted and finds good match.