GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Source parameter estmaton by using Q tomography: the potentality of exploitng large sequence of afershocks P. De Gori 1 , F. P. Lucente 1 , C. Chiarabba 1 1 Isttuto Nazionale di Geofsica e Vulcanologia (INGV), Rome, Italy The determinaton of seismic source parameters (seismic moment, source dimension, stress drop) play an important role in studying earthquake physics, for example to defne fault interacton or to predict the ground shaking. However, the measurement of earthquake source parameters is afected by large uncertaintes, and diferent approaches lead to large variability in results. One crucial aspect is the trade-of between atenuaton (Q) and corner frequency (fc) in spectral ftng. Here we describe a method to solve the trade-of based on the ft of displacement spectra to fnd the source characteristcs (corner frequency, fc, and the signal moment, Ω0) and the single-staton atenuaton operator (t), in additon to the site response. We follow a parametric approach based on the use of 3D Q seismic tomography and a bootstrap-based method for selectng the best spectra ft. The correcton of atenuaton with synthetc values derived by 3D atenuaton tomography efciently deals with the trade-of between source and path terms, leading to small uncertaintes in the determinaton of source unknowns (fc and signal moment, Ω0), thus yielding constrained estmates of source parameters for low- to medium-magnitude earthquakes. We show an applicaton to the Emilia 2012 seismic sequence, for which we computed the source parameters for 1240 afershocks (from an inital dataset of 1748) with local magnitude ranging from 2.0 to 4.7 using the spectral ft from P and S waves. This approach gives the opportunity to infer the mechanical state of a complete fault system by taking advantage of the larger number of low- magnitude events (with respect to the largest ones) that always follow a major earthquake. Corresponding author: pasquale.degori@ingv.it