1. Regulatory zoning, soil classification and importance coefficients

1.1 Regulatory zoning

Regulatory zoning defines five zones of increasing seismicity, based on communal divisions. Zone 5, which includes the Caribbean islands, corresponds to the highest level of hazard in France. Metropolitan France and the other French overseas departments have four seismic zones, ranging from zone 1, with very low seismicity (Aquitaine basin, Paris basin, etc.), to zone 4, with medium seismicity (Rhine trench, Alpine and Pyrenean massifs).

The parameter used to describe the seismic hazard at national level is a _gr , ground-to-rock acceleration (rocky ground is taken as the reference). Figure 1 illustrates...