An Empirical Model to Account for Spectral Amplification of Pulse-Like Ground Motion Records

• Published in: Geosciences (Basel) Vol. 11; no. 1; p. 15
• Main Authors: Sgobba, Sara, Lanzano, Giovanni, Pacor, Francesca, Felicetta, Chiara
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.01.2021
• Subjects: ground-motion model; near-fault directivity; pulse-like records; strong-motion database
• ISSN: 2076-3263; 2076-3263
• DOI: 10.3390/geosciences11010015

Near-source effects can amplify seismic ground motion, causing large demand to structures and thus their identification and characterization is fundamental for engineering applications. Among the most relevant features, forward-directivity effects may generate near-fault records characterized by a large velocity pulse and unusual response spectral shape amplified in a narrow frequency-band. In this paper, we explore the main statistical features of acceleration and displacement response spectra of a suite of 230 pulse-like signals (impulsive waveforms) contained in the NESS1 (NEar Source Strong-motion) flat-file. These collected pulse-like signals are analyzed in terms of pulse period and pulse azimuthal orientation. We highlight the most relevant differences of the pulse-like spectra compared to the ordinary (i.e., no-pulse) ones, and quantify the contribution of the pulse through a corrective factor of the spectral ordinates. Results show that the proposed empirical factors are able to capture the amplification effect induced by near-fault directivity, and thus they could be usefully included in the framework of probabilistic seismic hazard analysis to adjust ground-motion model (GMM) predictions.