In an attempt to develop a diffuse culture of prevention against earthquakes, the Italian government has issued an Act (June 24 2009 n. 77) and subsequent ordinances which regulate the distribution of resources to those regions that promote studies of seismic microzoning (SM). As a result, during the last years the number of Ital ian SM studies has been increasing and posing many new problems and challenges to administrators and scientists. The aim of this paper is to illustrate, through some salient examples of recent SM cases in Italy, the emerging philosophy of a new current of SM studies that can be called ordinary, namely projects devoted to seismic risk reduction through the usual preventive activities that can be carried out by local governments with the contribution of local officials and professionals, to the maximum extent possible. While the SM studies are generally elaborate, slow and costly, the logic of ordinary SM projects is that they have to be performed smoothly, rather quickly and cheaply. The aim is not to obtain the best SM product at any price but the best SM project consistent with efficient administrators who really want to reduce seismic risk in their regions.
In order to reach this objective and to guarantee the quality of the products, local governments (regions, provinces and municipalities) now have new duties; that is, they must undertake, in conjunction with scientists and researchers, positive actions to improve the state of knowledge and of practice in seismic risk reduction in the region, to increase the number and technical capacities of local professionals and public officials, to reduce time and investigation costs through drawing up basic geological maps also in digital format at an appropriate scale for SM, issuing specific valuable SM guidelines, implementing digital models of the territory, creating regional seismological, geological and geotechnical data banks, controlling the accuracy of the obtained SM maps and so on.
The paper focuses on unprecedented problems posed by the new legislation also to scientists and researchers, who are now called by administrators and public officials to play different scientific roles than in the past in order to contribute to advancing the frontiers of knowledge as well as the state of practice through experience transfer and applications.
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Local seismic response in presence of subsurface cavities
In this paper the effect of underground cavities on the seismic response under incident plane waves of volume and surface has been studied.The numerical solution is obtained using the boundary element method in the BESOIL /14/ computer code that allows a 2D analysis of propagation both of volume and Rayleigh waves, and any geometry of the cavity and the ground surface.The main parameters that govern the phenomenon of amplification are considered and the criteria for determining their importance are provided. Finally a realistic cavity of irregular shape has been examined for different values of its depth and dimension.
Damage analysis of the town of Onna (L’Aquila) after the April, 6, 2009 earthquake
The paper addresses the analysis of the seismic damage of Onna, a village near L’Aquila almost completely destructed during the 6 April event. A purposely developed data form has been used to collect the ob- servations of several surveyors. The analysis of the construction typologies, of the seismic vulnerability and of the damage lead to the conclusion that the poor characteristics of the masonry played a dramatic role in the seismic damage suffered by the buildings, despite that some typical historical seismic provisions were present (limited height of the buildings, wood ties). The low level of damage of some unreinforced masonry buildings in Onna, built following a good construction practice, indirectly confirms the heavy role played by the seismic vulnerability in the damage observed.
For this paper is available an extended abstract after the text in Italian.