OK, dick, ne abbiamo parlato in un precedente thread, le NEHRP 2009 citano un generico scalare ma non specificano che la PGA deve essere uguale per tutti.
Rimane il fatto che bisognerebbe conciliare la compatibilità richiesta dalla legge di M e R con il range di PGA inserito nella ricerca, non so se si può fare, bisognerebbe chiederlo a Madiai, però è chiaro, e su questo insistono tutti o quasi gli eminenti esperti, che i requisiti di disaggregazioen sono irrinunciabili (anche se sappiamo che a volte non possono essere rispettati rigidamente).
FEMA NEHRP 2009
3.3.1.4 Scale factors. The most commonly employed ground motion scaling method involves
multiplying all of the acceleration values of the time-acceleration pairs by a scalar value. This timedomain
scaling modifies the amplitude of the accelerations (to approximate changes in source magnitude
and/or distance) without affecting frequency content or phasing. Although not limited by the Provisions,
the scale factors applied to recorded ground motions should be modest (usually falling between 1/3 and
3); if very small or very large scale factors are needed, some aspect of the event that produced the source
motion likely is inconsistent with the maximum considered earthquake being modeled. An identical scale
factor is applied to both components of a given ground motion to avoid unrealistically biasing one
direction of response. Since the response spectra for time-domain scaled ground motions retain their
natural jaggedness, the acceptance criterion compares their average to the target spectrum, without
imposing limits on the scaling of individual ground motions. That means that there is no single set of
scale factors that may be applied to the selected ground motions (as discussed further in Provisions Part 2
Section C16.1.3.2)
