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Rischio sismico
OVERVIEW OF THE WORKSHOP “SEISMIC RISK IN THE PO PLAIN”
On Nov. 24th 2010, for the anniversary of the 2004 earthquake of Valsabbia and Garda, a workshop on “Seismic risk in the Po Plain” took place at Brescia. The conference was organized by CeSiA (Applied Seismology and Structural Dynamics Research Center), a research center of the University of Brescia, with the cooperation of the Museo Civico di Scienze Naturali of Comune di Brescia, which, moreover, hosted the meeting. The workshop belongs to a cycle which started in 2006 (information on the previous events is available at http://cesia.ing.unibs.it/).
The workshop topic, which respects the aims of CeSiA, is very interesting since the Po Plain includes areas of moderate but complex seismicity; some of these areas have only recently been classified as seismic by the norms. Thus researchers deem necessary both further geologic and seismologic studies and seis- mic risk assessments of an area characterized by an intense urbanization, which in great part occurred in the absence of adequate seismic rules.
After the opening by the President of CeSiA, Claudio Giorgi, by the Director of Museo Civico di Scienze Naturali, Paolo Schirolli, by the alderman for Culture of Comune di Brescia, Andrea Arcai, by the President of Ordine degli Ingegneri della Provincia di Brescia, Marco Belardi, the workshop, attended by about one hundred people (both technicians or professionals and researchers) included two sessions, “Seismic hazard in the Po Plain” and “Seismic Vulnerability in the Po Plain”.
This presentation briefly describes the workshop programme.
QUATERNARY FAULTS AND SEISMIC HAZARD IN THE LAKE GARDA AREA
Evidence of active tectonic shortening in the Lake Garda area (Northern Italy) has been very well described in the geological literature for at least 40 years, mainly due to the extensive research conducted during the siting of nuclear power plants in Lombardia in the 80’s. This area includes in fact the causative faults for some of the largest seismic events ever occurred in Northern Italy, i.e. the two medieval earthquakes of January 3rd, 1117 (Verona, Io = IX-X MCS) and the 25th of December, 1222 (Brescia, Io = IX-X MCS). More recently, two “twin” moderate events occurred at Salò on October 30th, 1901 (Io = VIII MCS) and November 24th, 2004
(Ml =5.4). This is therefore a critical area for understanding the relationship between tectonic structures and earthquake source parameters in the Po Plain. We address this issue through new field data and airphoto interpretation, morphobathymetric investigations in South Lake Garda, and a systematic revision of published data. A new map of Quaternary faults is presented, that shows a good correlation between Quaternary deformations, major regional tectonic structures, and macroseismic information derived from local strong seismic events. Style and rates of activity of the proposed capable faults allow us to infer the typical seismogenic features of the characteristic seismic event for the Lake Garda region, which can be regarded as the controlling earthquake for the seismic hazard of the central part of the Po Plain.
INDUCED SEISMICITY AND RELATED RISK IN ITALY
The seismicity induced by human activities is a subject almost unknown in Italy, with an average of published works on the subject at a fraction of a percentage of what is being published abroad. The first part of this paper discusses the historical reasons for this lack of interest, while the second will examine the implications in terms of seismic risk and possible regulations following the example of other European countries.
The Mapping of Post-Earthquake Damage Scenarios in Support of Municipal Emergency Plans
Nel presente lavoro viene proposta una metodologia, chiamata SCE-PEC, per la rappresentazione di scenari di danno post-sisma /1/, finalizzati agli obiettivi della pianificazione comunale dell’emergenza sismica /2,3/. Uno scenario di danno post-sisma contiene informazioni essenziali per la pianificazione delle attività delle Funzioni di Supporto /4,5/. Detta metodologia utilizza vari tipi di mappe con differenti livelli di elaborazione e sintesi: mappe di base, mappe di danno, mappe di sintesi e mappe per funzioni di supporto. La metodologia SCE-PEC è di tipo modulare e pertanto è possible applicarla parzialmente o integrarla con infor- mazioni aggiuntive.
For this paper is available an extended abstract after the text in Italian
Aggiornamento delle mappe di rischio sismico in Italia
Seismic risk maps updated on the basis of new data about real estate are presented in this paper. Previous maps were presented in 1996 by a specific workgroup appointed by Italian Civil Protection Department and they were used to make a list of municipalities at high seismic risk that were granted tax relief depending on vulnerability reduction interventions. Furthermore, those maps were updated with the hazard assessment developed after 1998. Real estate and population data resulted from Istat Census of 1991. In this updating, data from Istat Census of 2001 have been used, but hazard assessment and the methodology were the same of the previous maps, in order to evaluate the impact of a different structure of the real estate on risk assessment.
All the evidence makes it clear that the distribution and the overall assessment confirm the previous evaluation based on 1991 data, in spite of a 9% real estate increment, from 1991 to 2001. Specific data processing has pointed out differences in structural characteristics of the real estate from 1991 and 2001 Istat Census, reducing its estimated vulnerability, in compensation of the exposure increment due to the real estate increment.
This paper is available in Italian only.