Abstract
Abstract. The SiSeRHMap (simulator for mapped seismic response using a hybrid model) is a computerized methodology capable of elaborating prediction maps of seismic response in terms of acceleration spectra. It was realized on the basis of a hybrid model which combines different approaches and models in a new and non-conventional way. These approaches and models are organized in a code architecture composed of five interdependent modules. A GIS (geographic information system) cubic model (GCM), which is a layered computational structure based on the concept of lithodynamic units and zones, aims at reproducing a parameterized layered subsoil model. A meta-modelling process confers a hybrid nature to the methodology. In this process, the one-dimensional (1-D) linear equivalent analysis produces acceleration response spectra for a specified number of site profiles using one or more input motions. The shear wave velocity–thickness profiles, defined as trainers, are randomly selected in each zone. Subsequently, a numerical adaptive simulation model (Emul-spectra) is optimized on the above trainer acceleration response spectra by means of a dedicated evolutionary algorithm (EA) and the Levenberg–Marquardt algorithm (LMA) as the final optimizer. In the final step, the GCM maps executor module produces a serial map set of a stratigraphic seismic response at different periods, grid solving the calibrated Emul-spectra model. In addition, the spectra topographic amplification is also computed by means of a 3-D validated numerical prediction model. This model is built to match the results of the numerical simulations related to isolate reliefs using GIS morphometric data. In this way, different sets of seismic response maps are developed on which maps of design acceleration response spectra are also defined by means of an enveloping technique.
Highlights
In the scientific community, it is well known that lithologic stratigraphy as well as topographic features are capable of considerably amplifying the local destructive action of an earthquake (Del Prete et al, 1998; Athanasopoulos et al, 1999)
The hybrid model computes the mapping of seismic response using an adaptive model, which is trained on one-dimensional (1-D) seismic response target cases calculated from some shear wave velocity–thickness sequences
The results show a migration to high frequency that occurs when the regional shear velocity increases; this effect appears less evident for the peak that protrudes on the plain (3-D shape)
Summary
It is well known that lithologic stratigraphy as well as topographic features are capable of considerably amplifying the local destructive action of an earthquake (Del Prete et al, 1998; Athanasopoulos et al, 1999). The hybrid model computes the mapping of seismic response using an adaptive model, which is trained on one-dimensional (1-D) seismic response target cases calculated from some shear wave velocity–thickness sequences. These latter are uniformly randomly selected in coherence with general lithodynamic layered models assumed for the study area. In this way, the trained adaptive model, conceptually defined as a meta-model (replacement model), is used in the spatial predictive analysis, which aims at developing seismic response maps by means of its meta-model solving in the GCM
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