HR: 1340h
AN: S53B-1106    [Abstracts]
TI: Long-Term Earthquake Hazard and Uncertainty Assessment in a Moderately Seismic Area
AU: * Montaldo, V
EM: montaldo@mi.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, via Bassini 15, Milan, 20133 Italy
AU: Stucchi, M
S53B-1106 AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, via Bassini 15, Milan, 20133 Italy
AU: Albini, P
S53B-1106 AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, via Bassini 15, Milan, 20133 Italy
AU: Meletti, C
S53B-1106 AF: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, via Bassini 15, Milan, 20133 Italy
AB: This contribution focuses on the long-term earthquake hazard at the cities of Venice, Verona and Bergamo in Northern Italy, whose historical and cultural importance is widely known. However, as these cities are located in areas of moderate seismic activity, it is easy to forget that they experienced some severe earthquake shaking in the past. As a matter of fact, two events of moderate to large magnitude (Mw≥6) struck Northern Italy in the first two centuries of the past millennium. Despite the large amount of high quality historical, seismological and geological studies these events are still unconstrained, and their causative faults are debated. Moreover, geological studies indicate the presence of, at least, one seismogenic fault that might represent a seismic gap. This paper deals with seismic hazard assessment according to different methods, and it aims at evaluating the origin of the uncertainties that influence the results. Starting from the existing geological and seismological information, we computed seismic hazard for Bergamo, Verona and Venice by means of different probabilistic methods: i) the conventional Cornell-McGuire approach; ii) a spatial smoothing of seismicity, iii) a time-dependent method. The Cornell-McGuire method has been recently adopted to compile the seismic hazard map of Italy required by the enforcement of a new building code; the smoothed seismicity approach is based on the parametric earthquake catalogue only, while seismogenic sources capable of generating moderate to large earthquakes are used in the time-dependent approach along with large background areas. Seismic hazard has been computed for convenient return periods in order to show the contribution of strong and moderate seismicity and, above all, the differences between the time-independent and the time-dependent analyses. The extent to which the outcomes at the three cities of interest are affected by the uncertainties is discussed and quantified, by analyzing the seismic hazard curves computed for each site with the different methods. In areas of low or moderate seismicity, epistemic uncertainties play a fundamental role in seismic hazard assessment, mainly because they influence the results in a way that is comparable to that of the regional level of hazard.
DE: 6309 Decision making under uncertainty
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005