A ‘‘standard procedure’’ to characterize theseismic hazard of a given area was proposed. It is based ona multidisciplinary approach implying: (1) the knowledgeof the seismic history of the area; (2) detailed geologicalsurveys; (3)seismic noise measurements; (4) simulations ofearthquake scenarios. The downtown of Acireale, a typicalbaroque town located on Eastern Sicily, was chosen as the‘‘test area’’. A catalog of the local seismogenic faults (ableto generate earthquakes in historical times) has beencompiled, as well as a seismic catalog for the effects ofboth local and regional earthquakes. The analysis of bothcatalogs allowed us to make the following conclusions: (1)the most important seismogenic faults affecting theAcireale municipality do not affect the downtown, whilethe related local earthquakes attenuate their energy (andintensity) in short (few km) distances; (2) the highestseismic intensity (degree X) experienced in Acirealedowntown was caused by the 1693 regional earthquake; (3)over the last 140 years, the downtown has experienced thehighest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies a moderateseismic hazard. The estimation of the seismic hazard hasbeen also approached by the experimental method ofrecording seismic noise. Measurements have been performedat seven different sites, where drills gave detailedinformation on the shallow subsurface geology to obtainHV (horizontal/vertical) spectral ratios. On the whole, thehighest site amplification factor was moderate (about 7).A further investigation based on synthetic seismograms(and spectra) produced by simulating two given earthquakescenarios was also performed. The two scenarios are,respectively, representative of the largest expected earthquakein the area (the 1693 shock) and of a moderate(magnitude ca. 5.5) local earthquake (as the 1818 one).Moderate to strong locally expected accelerations wereevidenced.

A procedure to estimate the seismic hazard in an urban area: an application to Acireale (Eastern Sicily)

IMPOSA, Sebastiano;GRESTA, Stefano
2011-01-01

Abstract

A ‘‘standard procedure’’ to characterize theseismic hazard of a given area was proposed. It is based ona multidisciplinary approach implying: (1) the knowledgeof the seismic history of the area; (2) detailed geologicalsurveys; (3)seismic noise measurements; (4) simulations ofearthquake scenarios. The downtown of Acireale, a typicalbaroque town located on Eastern Sicily, was chosen as the‘‘test area’’. A catalog of the local seismogenic faults (ableto generate earthquakes in historical times) has beencompiled, as well as a seismic catalog for the effects ofboth local and regional earthquakes. The analysis of bothcatalogs allowed us to make the following conclusions: (1)the most important seismogenic faults affecting theAcireale municipality do not affect the downtown, whilethe related local earthquakes attenuate their energy (andintensity) in short (few km) distances; (2) the highestseismic intensity (degree X) experienced in Acirealedowntown was caused by the 1693 regional earthquake; (3)over the last 140 years, the downtown has experienced thehighest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies a moderateseismic hazard. The estimation of the seismic hazard hasbeen also approached by the experimental method ofrecording seismic noise. Measurements have been performedat seven different sites, where drills gave detailedinformation on the shallow subsurface geology to obtainHV (horizontal/vertical) spectral ratios. On the whole, thehighest site amplification factor was moderate (about 7).A further investigation based on synthetic seismograms(and spectra) produced by simulating two given earthquakescenarios was also performed. The two scenarios are,respectively, representative of the largest expected earthquakein the area (the 1693 shock) and of a moderate(magnitude ca. 5.5) local earthquake (as the 1818 one).Moderate to strong locally expected accelerations wereevidenced.
2011
Seismogenic faults; Local site amplification, H/V spectral ratios; Earthquake scenario simulations
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/21380
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