- Ground-motion model is: where Y is in cm∕s2 and Mref = 4.5; a = 3.7691, b1 = 0.0523, b2 = -0.1389, c1 = -1.9383, c2 = 0.4661,
h = 10.1057, C0 = 0, C1 = 0.2260, C2 = 0.1043, σeve = 0.2084, σsta = 0.2634 and σ = 0.3523 for
horizontal PGA using rjb; a = 3.2191, b1 = 0.1631, b2 = -0.0765, c1 = -1.7613, c2 = 0.3144, h = 9.1688,
C0 = 0, C1 = 0.1938, C2 = 0.1242, σeve = 0.2080, σsta = 0.1859 and σ = 0.3384 for vertical PGA
using rjb; a = 3.750, b1 = 0.1180, b2 = -0.1147, c1 = -1.9267, c2 = 0.4285, h = 10.0497, C0 = 0,
C1 = 0.2297, C2 = 0.1022, σeve = 0.2103, σsta = 0.2666 and σ = 0.3555 for horizontal PGA using
repi; and a = 3.2015, b1 = 0.2482, b2 = -0.0428, c1 = -1.7514, c2 = 0.2588, h = 9.1513, C0 = 0,
C1 = 0.1983, C2 = 0.1230, σeve = 0.1917, σsta = 0.1877 and σ = 0.3241 for vertical PGA using
- Use three site classes following Sabetta and Pugliese (1987, 1996):
- Rock. Corresponding to NEHRP A and B categories. 104 stations. S1 = 1 and S2 = S3 = 0.
- Shallow sediment: deposits thinner than or equal to 20m and thicker than 5m. V s of sediment lower
than 800m∕s. 47 stations. S2 = 1 and S1 = S3 = 0.
- Deep sediment: deposits thicker than 20m. 55 stations. S3 = 1 and S1 = S2 = 0.
Site classification performed using verified geological, geophysical and geotechnical information but of
varying detail. Note that classification between C1 and C2 is a simple but efficient method to identify sites
with amplifications at frequencies larger or smaller than 2–5Hz. Data from 206 different stations.
- Use four faulting mechanism classes:
- 50 earthquakes.
- 12 earthquakes.
- 17 earthquakes.
- 28 earthquakes.
Find that mechanism coefficients are not significantly different than zero and, therefore, remove them.
- Focal depths between 0 and 29.21km.
- Use data from Italian Accelerometric Archive (ITACA) from between 1972 and 2007, which have been
carefully revised during a project funded by the Italian Department of Civil Protection, plus some data
from the Northern Italy Strong Motion network (RAIS). Records individually processed using acausal
fourth-order Butterworth filters with cut-offs selected by visual inspection of Fourier spectra.
- Select records with rjb < 100km from earthquakes with Mw ≥ 4 recorded at two or more stations.
- Mw ≤ 6 are well sampled for rjb > 5km, particularly for 4 ≤ Mw ≤ 4.6. No data from rjb < 10km from
earthquakes with Mw > 6.
- Compare PGAs and rjb for common records with Sabetta and Pugliese (1987). For PGA find similar
values, indicating that the different processing applied results in consistent results. For rjb find significant
differences for distances shorter than 20km, which attribute to improvements in knowledge of source
- Examine inter-event and inter-station residuals. Find most inter-event errors are between -0.2 and 0.2
with a few events (e.g. 2002 Molise) with largely or over- or under-estimated.
- When comparing observations and predictions for Irpina (Mw6.9) 1980 earthquake state that comparisons
unreliable for rjb < 10km due to lack of data.
- Compare predictions and observations for the 23/12/2008 (Mw5.4) northern Apennines earthquake
mainshock to Parma and its Mw4.9 aftershock (both with focal depth > 20km and reverse mechanism),
which were not used to develop GMPEs. 33 records (32 ≤ repi ≤ 217km) of mainshock and 26
(9 ≤ repi ≤ 217km) records of aftershock. Find the most observations fall within ±1σ but some for
30 ≤ repi ≤ 60km are over-estimated by up to one order of magnitude.
- Note importance of improving site categorization to reduce σsta.