Source and high-frequency decay parameters for the Azores region for stochastic finite-fault ground motion simulations

• Published in: Bulletin of earthquake engineering 2016-07, Vol.14 (7), p.1885-1902
• Main Authors: Carvalho, A., Reis, C., Vales, D.
• Format: Article
• Language: English
• Subjects: Attenuation; Azores; Civil Engineering; Decay; Earth and Environmental Science; Earth Sciences; Earthquakes; Emergency preparedness; Environmental Engineering/Biotechnology; Fault lines; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Ground motion; Hydrogeology; Mathematical models; Original Research Paper; Quality factor; Seismic activity; Seismic engineering; Seismic hazard; Seismology; Simulation; Stresses; Structural Geology
• ISSN: 1570-761X; 1573-1456
• DOI: 10.1007/s10518-015-9842-y

Strong ground motion prediction based on finite-fault simulation requires the identification of the fault (strike, dip, length and width), source kinematics parameters (stress drop, rupture velocity and slip distribution), regional crustal properties (geometrical spreading, anelastic structure, and upper crustal amplification and attenuation parameters) and the determination of amplification effects due to the local site geology. The general purpose of this study is to understand source and attenuation properties in the Azores, by the determination of stress drop, quality factor and kappa, through records obtained by the Portuguese digital seismic and accelerometer network. Source Spectra were obtained, for each record, after correcting observed spectra from geometrical spreading and anelastic attenuation effect: quality factor was estimated based on coda decay in the time domain and the kappa parameter was estimated by fitting the high-frequency decay of the acceleration spectrum with a straight line in a log-linear scale. Mean stress drop value was obtained considering that ω-squared model for the source spectra prevails. Parameters kappa, k, and quality factor, Q, have been estimated to be k = (0.075 ± 0.02)s and Q ( f ) = ( 76 ± 11 ) f 0.69 ± 0.09 , respectively. A mean value of stress drop was estimated to be around 90–130 bars for the earthquakes in analysis. The knowledge of source and path parameters, in association with other ground motion parameters, allows improving ground-motion estimates for the Azores and, consequently, will lead to more accurate seismic hazard assessment for the Azores and better characterization of seismic scenarios.