- Ground-motion model is:
where Y is in cm∕s2, C1 = 0.125, C2 = 1.286, C3 = -1.133 and σ = 0.69. Only derive equation for firm
soil sites due to insufficient data for other classes. For compact rock sites propose using ratio between PGA
on firm soil and rock derived by Campbell (1997).
- Use three site classifications:
- Compact rock. Crystalline rocks (granite and basalt), metamorphic rocks (e.g. marble, gneiss, schist
and quartzite) and Cretaceous and older sedimentary deposits following criteria of Campbell (1997).
Similar to Spanish building code classes I and II with 400 ≤ V s ≤ 750m∕s. 23 stations.
- Alluvium or firm soil. Quaternary consolidated deposits. Similar to Spanish building code class III
with 200 ≤ V s ≤ 400m∕s. 29 stations.
- Soft sedimentary deposits. 52 stations.
Classify using crude qualitative descriptions.
- Most stations in basements of small buildings (e.g. city council offices) and therefore records are not truly
- Only consider data with 5 ≤ de ≤ 100km and M ≥ 3.
- Focal depths between 1 and 16km.
- Most data from 3 ≤ M ≤ 4 and de ≤ 50km. Only one record with M > 5 and de < 20km.
- Use hypocentral distance because no information on locations of rupture planes and since using hypocentral
distance automatically limits near-source ground motions.
- Do not consider style-of-faulting since no reported mechanisms are available for most events.
- Compare predicted PGA for Mw5 with observations for 4.9 ≤ Mw ≤ 5.1. Find reasonable fit.