Proposal of a system of spectrum intensity scales for the scaling of natural accelerograms accounting for hysteretic behaviour and local site conditions. A new system and its application on displacement-based design

The evolution of attenuation equations is an interesting aspect of the development of Engineering Seismology that has taken a long and fruitful road. Recently (2005), a robust attenuation model for Europe has been proposed by Ambraseys, Douglas, Sarma and Smith (ADSS). The ADSS model estimates the attenuation of spectral acceleration as a function of moment magnitude, source-to-site distance, faulting mechanism and local site conditions. On the other hand, past studies have shown that a good correlation exists between spectrum intensity (SI) and ductility demand. This indicates that SI can be used as an objective measure of instrumental intensity as efficient earthquake-resistant structures are expected to behave inelastically under the design earthquake. This article introduces a semiempirical model to estimate Housner Spectrum Intensity (SIH) in Europe. The proposed model is based on a parametric study on the variation of pseudovelocity spectra derived from a large family of acceleration spectra predicted by the ADSS model. Accordingly, the proposed model estimates the attenuation of SIH as a function of the same parameters of the ADSS model. Comparisons between observed and estimated SIH values are critically analyzed and the potential application of the proposed model for direct accelerogram scaling and vulnerability analysis is highlighted.