amplification factors

  • Uncategorized

    • Valutazione degli effetti di amplificazione sismica in piccoli bacini sedimentari per studi di pericolosità sismica locale a scala regionale

    Massimo Compagnoni, Floriana Pergalani, Daniela Di Bucci, Giuseppe Naso

    Parametric analyses for the evaluation of the local seismic response, in small sedimentary basins, are here presented. These analyses have been performed through 1D and 2D models, with the aim to point out a quick methodology for the evaluation of local seismic hazard of sedimentary basins and to include these effects in studies of seismic hazard at regional scale.
    The results of this study consist of specific tables where the amplification factor Fa is shown as depending on seismic zones, soil classes and thickness range of the deposits. The Fa related to the lithological effects was calculated for period ranges of 0.1-0.5 s, 0.5-1.0 s and 0.1-2.5 s. Moreover, for the period range 0.1-0.5 s, a specific value of DFa has been calculated to take in to account the geometrical effects of the basin. The Fa ranges allow has to define an increasing scale of the local seismic hazard suitable to single out areas characterized by different geological exposure to local seismic effects. These areas should be further analyzed at a more detailed scale.

    This paper is available in Italian only

  • Uncategorized

    • A methodology for the evaluation of site effects in an area of Lombardia Region (Italy)

    Floriana Pergalani, Massimo Compagnoni

    In the paper the application of a methodology for the evaluation of site effects in an area of Lombardia Region (Italy) is shown. The objective of the project was to develop a methodology that may be easily repeated, to take into account site effects in urban planning.
    Therefore, a series of geologic, geomorphologic, geotechnical and geophysical analyses have been carried out, to identify the areas affected by site effects and to characterize the litho-technical units. The expected seismic inputs have been individuated and numerical analyses using one-dimensional (1D) code, analyzing single soil columns, and two-dimensional (2D) codes, working with finite or boundary elements on sections, have been done. The results, in terms of amplification coefficients, as a ratio between spectral intensity calculated in the periods of 0.1-0.5s and 0.5-1.5s of output and input, give elements for planning, both for urban general choices and for building design. In fact the results of all the analyzed situations, provide some correlations between the geometric and geophysical characteristics of the sites and the values of the amplification coefficients. These correlations could be used as a tool for extrapolations in similar situations, when only the geologic, geophysical and geotechnical characteristics of a site are known.
    The procedure provides three level of widening: the 1° level, a qualitative analysis, gives the identification of the areas characterized by the local effect. The 2° level, through a semi-quantitative analysis, gives, when the geologic, geophysical and geotechnical characteristics of a site are know, the possible level of the expected amplifications, using the performed correlation curves. The 3° level, characterized by a quantitative analysis, necessary during the project design of strategic build or in the case in which the application of the 2° level show the inadequacy of the seismic code, gives a the response spectra applying during the project design phase
    The proposed procedure, furthermore, is characterized by a modularity that allows its implementation and up- dating.

    The complete paper is available in Italian only.