Publication Date:
2017-04-04
Description:
We evaluate the goodness of fit of attenuation relations commonly used
for the Italian national territory (Sabetta and Pugliese, 1996) by using the maximum
likelihood approaches of Spudich et al. (1999) and Scherbaum et al. (2004). According
to the classification scheme proposed by Scherbaum et al. (2004), the Sabetta
and Pugliese (1996) relationships show consistent discrepancies between the predicted
and the observed peak ground acceleration (PGA) at rock sites in the Umbria-
Marche region, central Italy; however, at soft sites the agreement between observations
and prediction is satisfactory. The bias of the residuals, computed with the
Sabetta and Pugliese (1996) models for PGA, peak ground velocity, (PGV) and pseudovelocity
response spectrum (PSV) (for Ml 4–6 and epicentral distances up to
100 km) is negative. This means that on the average, the predictions overestimate
the observations, but the overestimation decreases with increasing magnitude. Then,
we present regional predictive relations (UMA05) for maximum horizontal PGA,
PGV, and 5%-damped PSV, derived from the strong-motion data recorded in the
Umbria-Marche area and classified as to four site categories. The UMA05 attenuation
relationships for rock sites are
log10 (PGA) 2.487 0.534Ml 1.280 log10 (R2 3.942)0.5 0.268
log10 (PGV) 1.803 0.687Ml 1.150 log10 (R2 2.742)0.5 0.300
and
log10 (PGA) 2.500 0.544Ml 1.284 log10 Rh 0.292
log10 (PGV) 1.752 0.685Ml 1.167 log10 Rh 0.297,
where PGA is measured in fraction of g and PGV in centimeters per second, Ml is
the local magnitude in the range 4–6, R is the epicentral distance in the range 1–100
km, and Rh is the hypocentral distance in kilometers. We used the random effect
model (Brillinger and Priesler, 1985; Abrahamson and Youngs, 1992; Joyner and
Boore, 1993; Joyner and Boore, 1994) to estimate the component of variance related
to the earthquake-to-earthquake, station-to-station, and record-to-record variability,
and to quantify the benefit of introducing a site classification in the attenuation model
to reduce the variance. The introduction of the site classification in the attenuation
model allows a reduction of the station-to-station component of variability (from
0.19 to 0.14 for PGA, and from 0.21 to 0.18 for PGV). We also found that the recordto-
record component represents the largest contribution to the model uncertainty.
Description:
Published
Description:
984-1002
Description:
JCR Journal
Description:
reserved
Keywords:
Ground-Motion
;
04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
