The earthquake of 6 September 2002 and the seismic history of Palermo (Northern Sicily, Italy): Implications for the seismic hazard assessment of the city

Azzaro, Raffaele; Barbano, Maria Serafina; Camassi, Romano; D’Amico, S.; Mostaccio, A.; Piangiamore, Giovanna Lucia; Scarfì, L.

doi:10.1007/s10950-004-8930-2

Cited by 26 publications

(10 citation statements)

References 23 publications

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“…In sector B2, most intensities were 5 or higher. This higher level of shaking was confirmed by the observed damage in southeast Palermo (Azzaro et al, 2004). • In the southeastern sector, we reduced the observation scale to better resolve the effects of alluvial deposits and found a larger variation in intensity.…”

Section: Resultssupporting

confidence: 55%

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Investigation of Surface Geology and Intensity Variability in the Palermo, Italy, Urban Area after the 6 September 2002 Earthquake

Giammarinaro

Tertulliani

Galli

et al. 2005

Bulletin of the Seismological Society of America

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For the first time, a high-density macroseismic survey has been carried out in the city of Palermo, Italy, after the 6 September 2002, M w 5.9 earthquake. The aim was to investigate the spatial relationships and correlations between intensity data and surface geology. A very dense database has been created to store a large amount of macroseismic, stratigraphic, and geotechnical information. A Geographic Information Systems (GIS) tool, called City-GIS, enables data processing by instruments and research keys devoted to seismic hazard. The results show the feasibility of such procedures, especially for large cities where the surface geology critically influences the ground motion. Our analysis, made on the basis of more than 2000 intensity observations scattered in the Palermo urban area, demonstrates the role of the variable geology in the variability of shaking. Significant variations of intensity are related to the geometry of the geologic formations present in the area. Intensities increase by about one intensity class inside those city sectors where the stratigraphic succession is characterized by a thin layer of calcarenites overlying very thick layers of silty clayey sands. Major amplification of up to two classes occurs in alluvial deposits in the southeastern part of Palermo, as expected. These results extend our knowledge of the seismic response in the outskirts of Palermo, which until now, was limited to the city center.

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Section: Resultssupporting

confidence: 55%

“…In spite of its epicentral distance and moderate magnitude, the earthquake provoked much alarm and fear in Palermo. In some cases, light damage occurred, especially in historical buildings and churches in the center and in southeastern parts of the city (Azzaro et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Investigation of Surface Geology and Intensity Variability in the Palermo, Italy, Urban Area after the 6 September 2002 Earthquake

Giammarinaro

Tertulliani

Galli

et al. 2005

Bulletin of the Seismological Society of America

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“…The maximum magnitude recorded in the belt during the last decades has been 5.9 (i.e., the 6 September 2002 earthquake; earthquake 14 in Table 1). Also, recent reviews of historical data [e.g., Guidoboni et al , 2003; Azzaro et al , 2004; Working Group CPTI, Catalogo parametrico dei terremoti Italiani, versione 2004 (CPTI04), Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy, 2004, available at http://emidius.mi.ingv.it/CPTI04/] have led to estimate offshore locations (i.e., within the south Tyrrhenian belt) and magnitude values of about 6 for the three earthquakes (1726, 1823 and 1940), which, during the last five centuries, have produced the most severe effects along the northern coast of Sicily.…”

Section: Discussionmentioning

confidence: 99%

Seismotectonics of the Nubia plate compressive margin in the south Tyrrhenian region, Italy: Clues for subduction inception

Billi¹,

Presti²,

Faccenna³

et al. 2007

J. Geophys. Res.

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[1] Seismological and structural data are used to constrain the active tectonics of the Nubia plate compressive margin in southern Italy. In this region, compressional displacements have resumed at the rear of the Maghrebian orogenic wedge since about 700-500 ka and are presently accommodated along a seismic belt in the south Tyrrhenian area, where a passive margin has developed during late Neogene-Quaternary times. Earthquake data from the south Tyrrhenian belt are analyzed with Bayloc, a probabilistic nonlinear location method. Results show that the seismic belt is segmented and involves a series of NE-SW and NW-SE elongated clusters. The NE-SW clusters are interpreted as high-angle reverse fault zones verging toward the southeast, whereas the perpendicular clusters are interpreted as possible strike-slip fault zones transferring the contractional displacements to advanced segments of the belt in the southeast. Brittle deformations observed in the Quaternary volcanic island of Ustica are consistent with the geometry and kinematics of the seismic belt deduced from the seismological data. The south Tyrrhenian active belt may constitute an early stage of subduction of the Tyrrhenian oceanic crust beneath Sicily. A similar scenario has been hypothesized also for the westward prolongation of the south Tyrrhenian belt off the Algerian coast. By integrating instrumental and historical seismic data with tectonic evidences, we infer that the south Tyrrhenian belt is probably capable of producing earthquakes with a maximum size close to magnitude 7. The analyzed data suggest a multifault system behavior for the studied compressional belt. This inference is important to estimate and mitigate the seismic and tsunamic hazards in such a densely populated region.

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“…On 6 September 2002, an M w 5.9 earthquake (40 km offshore) caused damage of European macroseismic scale (EMS-98, see Grünthal, 1998) intensity V-VI in downtown Palermo and in its southern sector, the Oreto River valley (Azzaro et al, 2004). Apart from some churches and historical buildings in the city center, few structures were seriously damaged.…”

Section: Geological Setting and Felt Seismicitymentioning

confidence: 99%

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage

Cara¹,

Cultrera²,

Azzara³

et al. 2008

Bulletin of the Seismological Society of America

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This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two riverbeds masked by urbanization since the seventeenth century. HVNSRs show significant variations in the study area: when the transition stiff to soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1-2 Hz, and exceeding a factor of 3 in amplitude. Using available information on subsurface geological structure, we compute theoretical 1D and 2D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling.The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European macroseismic scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5-3 Hz) and the occurrence of the highest damage grades. This approach allows us (1) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes, which separates zones of light damage from zones of significant damage, and therefore (2) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements.

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The earthquake of 6 September 2002 and the seismic history of Palermo (Northern Sicily, Italy): Implications for the seismic hazard assessment of the city

Cited by 26 publications

References 23 publications

Investigation of Surface Geology and Intensity Variability in the Palermo, Italy, Urban Area after the 6 September 2002 Earthquake

Investigation of Surface Geology and Intensity Variability in the Palermo, Italy, Urban Area after the 6 September 2002 Earthquake

Seismotectonics of the Nubia plate compressive margin in the south Tyrrhenian region, Italy: Clues for subduction inception

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage

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