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1 GeoSisLab
Dipartimento di Scienze
della Terra
Università degli Studi "G.
D'Annunzio"
Via dei Vestini, 30
66013 Chieti Scalo (CH)
Italy
b.pace{at}unich.it
g.lavecchia{at}unich.it
p.boncio{at}unich.it
(B.P.,
G.L., P.B.)
2 Istituto Nazionale di Oceanografia e
di Geofisica Sperimentale (OGS)
Borgo Grotta Gigante 42/c
34010 Sgonico
(TS)
Italy
lperuzza{at}inogs.it
(L.P.)
We defined a seismogenic model for central Italy based on three layers of
sources and computed the relative seismic-hazard maps. One layer is constituted
by individual structures liable to generate major earthquakes (M
5.5). We defined them as seismogenic boxes by using geological information
in terms of plan projection of active faults; the seismicity rates associated
with an individual source are based on the geometry and kinematics of the fault;
the recurrence model is controlled by the earthquake-source association, and,
when possible, we defined the occurrence time of the last major event, using it
in a time-dependent approach. Another layer is given by the instrumental
seismicity analysis of the past two decades, which allows us to evaluate the
background seismicity (M 
<5.5); using a sliding-window
selection of events, we defined a model of regular adjacent cells of variable
a and b values of the Gutenberg-Richter relation. The last
layer utilizes all the instrumental earthquakes and the historical events not
correlated to known structures (4.5 < M <6),
by separating them into seismotectonic provinces shaped on a
geological-structural basis. The seismic-hazard computations first use this
layered model in a traditional probabilistic scheme. The results indicate a
narrow belt of peak ground acceleration (PGA) higher than
0.30g (with standard deviation in attenuation functions) in the axial
part of the Apennine chain, with a maximum spot of PGA
>0.40g southeast of the area damaged by the 1997–1998
Umbria-Marche sequence (PGA expected not to be exceeded in 50 years
at 90% probability level). The background seismicity gives a nonnegligible
contribution to the hazard, at least for first damage levels. Then, a simplified
time-dependent hypothesis has been introduced for the individual sources alone,
computing the conditional probability of occurrence of characteristic
earthquakes for each source by Brownian passage time distributions. Adopting
equivalent fictitious seismicity rates, we obtained maps referring to the next
50 years by using traditional codes. These results show that the contribution of
the recently active sources vanishes, and the most hazardous sites are now
located south of L'Aquila and in the Sulmona area. We consider that the
methodology and results obtained are useful for seismic risk reduction
strategies.
This article has been cited by other articles:
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  W. Marzocchi Comment on "Layered Seismogenic Source Model and Probabilistic Seismic-Hazard Analyses in Central Italy" by Bruno Pace, Laura Peruzza, Giusy Lavecchia, and Paolo Boncio Bulletin of the Seismological Society of America, October 1, 2007; 97(5): 1763 - 1765. [Full Text] [PDF]
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L. Peruzza, B. Pace, G. Lavecchia, and P. Boncio Reply to "Comment on 'Layered Seismogenic Source Model and Probabilistic Seismic-Hazard Analyses in Central Italy' by B. Pace, L. Peruzza, G. Lavecchia, and P. Boncio" by W. Marzocchi Bulletin of the Seismological Society of America, October 1, 2007; 97(5): 1766 - 1768. [Full Text] [PDF]
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B. Pace, L. Peruzza, G. Lavecchia, and P. Boncio Layered Seismogenic Source Model and Probabilistic Seismic-Hazard Analyses in Central Italy Bulletin of the Seismological Society of America, August 1, 2006; 96(4A): 1567 - 1567. [Full Text] [PDF]
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