GNGTS 2013 - Atti del 32° Convegno Nazionale

For this work we assume that p =4 and that Δσ = 10 MPa at M w =3. Tab. 1 provide the parameters of our working model. An important goal of this research it will be represented by the study on source scaling. We will perform this task by using a technique based on the analysis of source spectral ratios. Numerous studies were published by Malagnini, Mayeda, and co-workers on all tectonic envi- ronments (normal, strike-slip, and reverse), but no data have yet been analyzed on subduction earthquakes; for this reason, the present data set is thus of special interest. Conclusions. The prediction of the earthquake ground motion has always been of primary interest for seismologists and structural engineers. For engineering purposes it is necessary to describe the ground motion according to certain number of ground motion parameters such as: amplitude, frequency content and duration of the motion. However, it is necessary to use more than one of these parameters to adequately characterize the ground motion excited by a specific source, and observed at a specific site. In order to do that, we analyzed data set acquired by portable network installed to monitor the aftershocks of the Maule earthquake to validate the analysis procedure. Tab. 1 – Parameters of our working model. M w Δσ (M Pa) 3.0 10 3.5 15.4 4.0 23.7 4.5 35.6 5.0 56.2 5.5 86.6 6.0 133.4 6.5 205.4 This study provides a unique opportunity to quantify high-frequency earthquake ground motion in a subduction zone due to the quality and quantity of observations in the frequency and distance range of 0.2-30 Hz and 40-500 km, respectively. The analysis was done using a two-step modeling procedure: 1) a regression is performed to characterize source duration and excitation, source-receiver distance dependence, and station site effects; 2) a point-source forward model is constructed in terms of geometrical spreading, observed duration, site effects, and source scaling, in order to match the regression results. This procedure may provides the necessary point source parameters for a stochastic finite-fault modeling of the ground motions for future large earthquakes in this subduction zone. A proper description of ground motion scaling requires presenting enough information to duplicate the observations. This means that, until definitive information will be available on source scaling and absolute site effects, Q( f ) cannot be presented without also being coupled to g(r) and κ. Acknowledgements. We are grateful to IRIS for providing all the data used in this research. We would like to thank to Dr. Kendra L. Johnson for collecting the data set for the RMTs solutions. We thank Dr. Harley Benz for his comments about this work. Fig. 1 was produced using the Generic Mapping Tools (Wessel and Smith, 1995). 92 GNGTS 2013 S essione 1.1