- Ground-motion model is: where for horizontal peak acceleration ah is in cm∕s2, a1 = 4000, a2 = 20, a3 = 16 and a4 = 0.63 for soil
sites a5 = -2.02 and a6 = 0.8 and for rock sites a5 = -2.11 and a6 = 0.79 (σ not given). For vertical peak
acceleration on soil sites av is in cm∕s2 a1 to a3 are same as horizontal and a4 = 0.48, a5 = -1.75 and
a6 = 0.53 (σ not given).
- Use two site categories (from original of four) for which derive two separate equations:
- Rock: mainly category (2) a) loose igneous rocks (tuffs), friable sedimentary rocks, foliated
metamorphic rock and rocks which have been loosened by weathering, b) conglomerate beds,
compacted sand and gravel and stiff clay (argillite) beds where soil thickness > 60m from bed rock.
- Soil: mainly category (4) a) soft and wet deposits resulting from high level of water table, b) gravel
and sand beds with weak cementation and/or uncementated unindurated clay (clay stone) where soil
thickness > 10m from bed rock. 54 records.
- Focal depths between 10 and 69km.
- Find equations using hypocentral distance but find that poor fit for Rudbar (Manjil) earthquake (Ms = 7.7)
which conclude due to use of hypocentral rather than rupture distance.
- Find equations using rupture distance
for Rudbar (Manjil) earthquake and hypocentral distances for other earthquakes. Coefficients given above.
They conclude that it is important that equations are derived using rupture distance rather than hypocentral
distance because most destructive earthquakes rupture surface in Iran.
- Do not know physical meaning of H term but find that it causes curves to fit data better.