Ground-Motion Scaling in Eastern Sicily, Italy

Abstract

We describe the characteristics of crustal wave propagation in eastern Sicily by using the background seismicity of the area. We follow the approach de- scribed by Malagnini, Hermann, and Di Bona (2000) and Malagnini et al. (2002). Our data set consists of 106 earthquakes recorded by nine three-component digital seismic stations between 1994 and 2001. We used only crustal events (depths shal- lower than 25 km), with local magnitudes ranging from 1.0 to 4.3, and hypocentral distances from 10 to 130 km. Peak ground velocities from 1311 narrow bandpass-filtered waveforms are mea- sured in thefrequency range 1.0-16.0 Hz,and regressedtodefinecrustalpropagation, excitation, and site characteristics, with respect to a reference station. A subsequent modeling effort is carried out, through the use of random vibration theory (RVT), for obtaining a quantitative evaluation of the apparent geometrical spreading g(r), and of the crustal quality factor Q(f). An attenuation parameter, j0, is also evaluated relative to a reference rock site. The attenuation and source parameters estimated in this study are used through the RVT in order to predict the peak horizontal ground acceleration (PGA), and the 5% damping pseudoacceleration spectra (PSA).