Seismic microzonation studies of Level 3 involve in-depth analysis in order to define the characteristics of the local seismic response through numerical simulations. A critical stage in such a procedure is the definition of the seismic input, a set of accelerograms representative of the ground motion locally expected at the bedrock for seismic scenarios most contributing to the local seismic hazard. However, in strong motion databases there may be insufficient availability of recordings that, for certain scenarios, satisfy spectrum-compatibility requirements. A new approach is proposed to solve this problem by integrating 4 real accelerograms with 3 simulated ones, calculated with the non-stationary stochastic procedure proposed by Sabetta et al. (2021). The simulated accelerograms are selected among a large number of them, stochastically generated for relevant seismic scenarios. The new procedure is organized into different steps. First, the spectral parameters of the local design spectrum used as reference are defined according to the local building code provisions (for Italy, cf. Ministero delle Infrastrutture e dei Trasporti, 2018). Then, a seismic hazard disaggregation analysis provides the earthquake parameters (magnitude, source distance and style of fault) of a number of seismic scenarios most contributing to the basic seismic hazard: for such scenarios, real accelerograms are extracted from available accelerometric databases. The final seismic input is provided by a code that optimizes the selection of 4 accelerograms, among the real ones extracted, and 3 simulated accelerograms, among a large number of them obtained for all the previously identified scenarios, so to best fit the design spectrum. This allows to cover relevant scenarios not represented by the real recordings and to improve the median spectrum compatibility of the total set of accelerograms. The procedure has been applied to the 84 Apulian municipalities involved in seismic microzonation studies. For each seismic input, the spectrum-compatibility has been verified, with special reference to the tolerance limits prescribed by the Italian Building Code, which admits deviations only between -10% and +30% from the design spectrum. The compliance with such rules was checked on the mean response spectrum of the accelerogram set. This was first regularized so to conform to the standard spectral shape required by the Code, according to the procedure recommended by national technical bodies (cf. Commissione Tecnica per la Microzonazione Sismica, 2022). The effectiveness of the seismic inputs so obtained was finally tested through 1D modelling of the local seismic response in a variety of geological and seismo-tectonic contexts, carried out by the code STRATA (Kottke et al., 2013). In such modelling, set of accelerograms provided by this new procedure and by the tools currently in use for this purpose were comparatively adopted.
Accelerogram selection for site response modelling in seismic microzonation
Casarano D.;
2024
Abstract
Seismic microzonation studies of Level 3 involve in-depth analysis in order to define the characteristics of the local seismic response through numerical simulations. A critical stage in such a procedure is the definition of the seismic input, a set of accelerograms representative of the ground motion locally expected at the bedrock for seismic scenarios most contributing to the local seismic hazard. However, in strong motion databases there may be insufficient availability of recordings that, for certain scenarios, satisfy spectrum-compatibility requirements. A new approach is proposed to solve this problem by integrating 4 real accelerograms with 3 simulated ones, calculated with the non-stationary stochastic procedure proposed by Sabetta et al. (2021). The simulated accelerograms are selected among a large number of them, stochastically generated for relevant seismic scenarios. The new procedure is organized into different steps. First, the spectral parameters of the local design spectrum used as reference are defined according to the local building code provisions (for Italy, cf. Ministero delle Infrastrutture e dei Trasporti, 2018). Then, a seismic hazard disaggregation analysis provides the earthquake parameters (magnitude, source distance and style of fault) of a number of seismic scenarios most contributing to the basic seismic hazard: for such scenarios, real accelerograms are extracted from available accelerometric databases. The final seismic input is provided by a code that optimizes the selection of 4 accelerograms, among the real ones extracted, and 3 simulated accelerograms, among a large number of them obtained for all the previously identified scenarios, so to best fit the design spectrum. This allows to cover relevant scenarios not represented by the real recordings and to improve the median spectrum compatibility of the total set of accelerograms. The procedure has been applied to the 84 Apulian municipalities involved in seismic microzonation studies. For each seismic input, the spectrum-compatibility has been verified, with special reference to the tolerance limits prescribed by the Italian Building Code, which admits deviations only between -10% and +30% from the design spectrum. The compliance with such rules was checked on the mean response spectrum of the accelerogram set. This was first regularized so to conform to the standard spectral shape required by the Code, according to the procedure recommended by national technical bodies (cf. Commissione Tecnica per la Microzonazione Sismica, 2022). The effectiveness of the seismic inputs so obtained was finally tested through 1D modelling of the local seismic response in a variety of geological and seismo-tectonic contexts, carried out by the code STRATA (Kottke et al., 2013). In such modelling, set of accelerograms provided by this new procedure and by the tools currently in use for this purpose were comparatively adopted.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
