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Task 3.2: Local Geology Effect on Seismic Hazard
Author(s)
Other Titles
Terremoti probabili in Italia tra il 2000 e il 2030: elementi per la definizione di priorità per la riduzione del rischio sismico
Sponsors
Gruppo Nazionale per la Difesa dai Terremoti
Language
Italian
Obiettivo Specifico
1.1. TTC - Monitoraggio sismico del territorio nazionale
Status
Unpublished
Peer review journal
No
Issued date
2003
Keywords
Abstract
The main purpose of Task 3.2 was to introduce the role of local geology in the seismic hazard evaluation at national scale. This was achieved by grouping the geological formation of the 1:500,000 Italian geological map into three classes A, B, C according to the EuroCode8 provisions (GCM, Geological-Class Map). These classes are associated to a variation of the ground motion due to the different seismic properties of the lithologies included in each group (ANNEX 1).
For a critical evaluation of the proposed approach, we have checked the occurrence of a systematic increment of macroseismic intensity as a function of the geological classes at a national scale. The study of distribution of Intensity anomalies associated to the 3 classes show a statistical significant tendency of positive anomalies to be related to classes B and C and negative anomalies to be related to class A (ANNEX 2).
We then assumed that the effect of local geology on ground motion is the one described by variation of elastic response spectra prescribed by EC8 (in terms of PGA, PSA, Housner Intensity). This variation is controlled by a set of parameters depending on the soil classes and earthquake magnitude (ANNEX 3).
We compared the increment factors to those deriving from a numerical simulation of the Città di Castello (Central Italy) basin where many geological and seismological data were available. The results at local scale show a good fit (within a factor of two) with the variations of hazard parameters for classes B e C (ANNEX 4).
Moreover, we launched a national-scale enquiry over the 8101 Italian Municipalities whose main goal was the estimation of the buildings distribution on the three soil classes corresponding to those of the CGM. We collected and organized the received forms in a database (see product 3). The comparison at a Municipality-scale of the GCM and the questionnaire results shows that their information is complementary, the first referring this percentage to the housing, the latter considering all the municipality territory (ANNEX 5). The questionnaire is a good data gathering tool for pointing out area where more detailed microzonation investigation must be performed. The questionnaire can be a powerful tool to increase awareness of Municipality Administration and the lack of involvement could be overcome by coordination at the Region levels.
Products
1. National geologic map at 1:500,000 scale modified according to the EC8 soil classes (geological-class map, GCM)
2. Map of the geology-dependent correction of hazard parameters
3. Database of the Italian municipalities containing information about the distribution of buildings in relation to the surface geology as well as geographical and geotechnical data availability.
The three products are organized in an attached CD and they are included in the GIS of the project.
For a critical evaluation of the proposed approach, we have checked the occurrence of a systematic increment of macroseismic intensity as a function of the geological classes at a national scale. The study of distribution of Intensity anomalies associated to the 3 classes show a statistical significant tendency of positive anomalies to be related to classes B and C and negative anomalies to be related to class A (ANNEX 2).
We then assumed that the effect of local geology on ground motion is the one described by variation of elastic response spectra prescribed by EC8 (in terms of PGA, PSA, Housner Intensity). This variation is controlled by a set of parameters depending on the soil classes and earthquake magnitude (ANNEX 3).
We compared the increment factors to those deriving from a numerical simulation of the Città di Castello (Central Italy) basin where many geological and seismological data were available. The results at local scale show a good fit (within a factor of two) with the variations of hazard parameters for classes B e C (ANNEX 4).
Moreover, we launched a national-scale enquiry over the 8101 Italian Municipalities whose main goal was the estimation of the buildings distribution on the three soil classes corresponding to those of the CGM. We collected and organized the received forms in a database (see product 3). The comparison at a Municipality-scale of the GCM and the questionnaire results shows that their information is complementary, the first referring this percentage to the housing, the latter considering all the municipality territory (ANNEX 5). The questionnaire is a good data gathering tool for pointing out area where more detailed microzonation investigation must be performed. The questionnaire can be a powerful tool to increase awareness of Municipality Administration and the lack of involvement could be overcome by coordination at the Region levels.
Products
1. National geologic map at 1:500,000 scale modified according to the EC8 soil classes (geological-class map, GCM)
2. Map of the geology-dependent correction of hazard parameters
3. Database of the Italian municipalities containing information about the distribution of buildings in relation to the surface geology as well as geographical and geotechnical data availability.
The three products are organized in an attached CD and they are included in the GIS of the project.
References
ENV 1998-1-1, EUROCODE 8, Design Provisions for Earthquake Resistance of Structures. Seismic actions and general requirements of structures. CEN/TC 250, Draft 4, December 2001.
Servizio Geologico Nazionale. Carta Geologica d’Italia al 500,000. Servizio Geologico Nazionale editor, 1978.
Housner GW (1952). Spectrum intensities of strong motion earthquakes. Proceeding of the Symposium on Earthquakes and Blast Effects on Structures. Earth. Eng. Res. Inst., Kohavi R. and Provost F (1998). Glossary. ML Journal, page 272, 1998.
Pergalani F., M. Compagnoni, and V. Petrini (2002): Valutazione degli effetti di sito tramite analisi numeriche e sperimentali nell'abitato di Città di Castello: analisi, confronti e utilizzo dei risultati. Ingegneria Sismica, 1, 66-77 (in Italian with English abstract).
Bordoni P., G. Cultrera, L. Margheriti, P. Augliera, G. Caielli, M. Cattaneo, R. de Franco, A. Michelini, and D. Spallarossa (2003). A microseismic study in a low seismicity area: the 2001 site-response experiment in the Città di Castello basin (Italy). Annals of Geophysics, VOL. 46, N. 6, December 2003.
Caserta, A., 1998. A time domain finite-difference technique for oblique incidence of antiplane waves in heterogeneous dissipative media. Annali di Geofisica 41, 617-631.
Caserta, A., Ruggiero V., Lanucara P., 2002. Numerical Modelling of dynamical interaction between seismic radiation and near-surface geological structures: a parallel approach.Computer & Geosciences, 28/9, 1071-1079.
Caserta A., Giuffrida C., Ruggiero V., Lanucara P., Firmani B. 2004. Input Data Web Interface for Numerical Simulations of Seismic Wave Propagation. ESC XXIX General Assembly Abstract Books, pp. 85.
Crespellani T., C. Madiai, and G. Simoni (2002). Indagini geotecniche per la valutazione degli effetti di sito in alcuni centri dell'Alta Valtiberina, Ingegneria Sismica, 1, 15-32 (in Italian with English abstract).
Sabetta F. and A. Pugliese (1996). Estimation of response spectra and simulation of nonstationary earthquake ground motions. Bulletin of Seismological Society of America, 86-2, 337-352.
Mucciarelli M., Spinelli A. and F. Pacor (2004). Un programma per la generazione di accelerogrammi sintetici "fisici" adeguati alla nuova normativa. Proceedings of XI National Congress of Italian National Association of Earthquake Engineering, ANIDIS, "L'ingegneria sismica in Italia", Genova 25-29 January 2004.
Servizio Geologico Nazionale. Carta Geologica d’Italia al 500,000. Servizio Geologico Nazionale editor, 1978.
Housner GW (1952). Spectrum intensities of strong motion earthquakes. Proceeding of the Symposium on Earthquakes and Blast Effects on Structures. Earth. Eng. Res. Inst., Kohavi R. and Provost F (1998). Glossary. ML Journal, page 272, 1998.
Pergalani F., M. Compagnoni, and V. Petrini (2002): Valutazione degli effetti di sito tramite analisi numeriche e sperimentali nell'abitato di Città di Castello: analisi, confronti e utilizzo dei risultati. Ingegneria Sismica, 1, 66-77 (in Italian with English abstract).
Bordoni P., G. Cultrera, L. Margheriti, P. Augliera, G. Caielli, M. Cattaneo, R. de Franco, A. Michelini, and D. Spallarossa (2003). A microseismic study in a low seismicity area: the 2001 site-response experiment in the Città di Castello basin (Italy). Annals of Geophysics, VOL. 46, N. 6, December 2003.
Caserta, A., 1998. A time domain finite-difference technique for oblique incidence of antiplane waves in heterogeneous dissipative media. Annali di Geofisica 41, 617-631.
Caserta, A., Ruggiero V., Lanucara P., 2002. Numerical Modelling of dynamical interaction between seismic radiation and near-surface geological structures: a parallel approach.Computer & Geosciences, 28/9, 1071-1079.
Caserta A., Giuffrida C., Ruggiero V., Lanucara P., Firmani B. 2004. Input Data Web Interface for Numerical Simulations of Seismic Wave Propagation. ESC XXIX General Assembly Abstract Books, pp. 85.
Crespellani T., C. Madiai, and G. Simoni (2002). Indagini geotecniche per la valutazione degli effetti di sito in alcuni centri dell'Alta Valtiberina, Ingegneria Sismica, 1, 15-32 (in Italian with English abstract).
Sabetta F. and A. Pugliese (1996). Estimation of response spectra and simulation of nonstationary earthquake ground motions. Bulletin of Seismological Society of America, 86-2, 337-352.
Mucciarelli M., Spinelli A. and F. Pacor (2004). Un programma per la generazione di accelerogrammi sintetici "fisici" adeguati alla nuova normativa. Proceedings of XI National Congress of Italian National Association of Earthquake Engineering, ANIDIS, "L'ingegneria sismica in Italia", Genova 25-29 January 2004.
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