where PGA is in g, a1= -3.93, a2= 0.78, a3= -1.5 and σ = 0.55.
All records from stiff bedrock. Shear-wave velocities estimated from geology gives: 1200–2000m∕s for
carbonated formations and > 2500m∕s for eruptive formations (majority of data).
Derive equation since find previous equations are not consistent with recent data recorded in France and
because of differences between ML of LDG and other ML scales.
Use data from the Alps, the Pyrenees and Armorican Massif recorded by LDG network of vertical
seismometers between 1995 and 1996. Convert vertical PGAs to horizontal PGAs using empirical relation
of Smit (1998).
Focal depths between 2 and 12km.
11 records from 3 ≤ de≤ 50km, 34 from 50 < de≤ 200km and 18 from de> 200km (all from two largest
earthquakes with ML5.3 and ML5.6).
Plot predictions and data from rock sites of all French earthquakes with ML≥ 4 recorded by RAP network
(largest three earthquakes have ML5.5, ML5.7 and ML5.9) and find good agreement. State that this
agreement shows that equation can be extrapolated to strongest earthquakes considered for France.
Note that it will be possible to establish a more robust equation using increasing number of data from
RAP, especially from near field and large magnitudes.