GNGTS 2016 - Atti del 35° Convegno Nazionale

384 GNGTS 2016 S essione 2.2 We surveyed AF along the segment of our study area and observed that the fault trace is marked by creep-induced damage to man-made features occurring along the fault strike. The NNW–SSE S. Caterina fracturing zone moved during several creep episodes. The pink house (Fig. 2a) depicted in the picture was restored several times during the last decade as well as the chapel (Fig. 2b and Fig. 2d), but recent creep movements again fractured them. Other recent creep phenomena were observed at via Pianeto and near the Camping (Fig. 2 e and Fig. 2e). Creep rates, obtained from analysis of historical records and field survey on 16 sites along the Timpe fault systems (Rasà et al., 1996), vary considerably from 0.5 to 2.3 cm/year. The authors found that two different type of aseismic slip are recognized: (1) a near-continuous, long period movement along some aseismic segments of faults and (2) intermittent, short-lived, pre and post-seismic movement related to seismically active fault segments. Method. For the HVSR analysis, we recorded ambient noise at 30 sites (Fig. 3a) using a 3-component seismometer (Tromino). Time series of ambient noise, having a length of 30 minutes, were recorded with a sampling rate of 128 Hz and, following the guidelines suggested by the SESAME project (2004) they were divided in different time windows of 20 s each not overlapping each other. A 5% cosine taper was applied to each window and the Fourier spectra were calculated. The spectra of each window were smoothed using a Konno-Ohmachi window (Konno and Ohmachi, 1998) fixing the parameter b to 40. Finally, the resulting HVSR, in the frequency range 0.5-20.0 Hz, was computed estimating the logarithmic average of the spectral ratio obtained for each time window, selecting only the most stationary and excluding transients associated to very close sources. Fig. 1 – a) Tectonic framework of Mount Etna; the black rectangle to the South of Acireale shows the location of Fig. 1d. Inset b) shows location and theAfrica–Eurasia plate configuration; inset c shows the main domains and structural elements of eastern Sicily: CA Calabrian arc, AMTB Apennine–Maghrebian thrust belt, MEF Malta escarpment fault system; dashed rectangle shows the location of Fig. 1a. d) Geological map and landslides distribution in the area of Acireale Fault. TDMF Timpa di Don Masi Formation (S. Caterina member), TF Timpa Formation, PF Pietracannone Formation, PPF Piano Provenzana Formation, PGF Portella Giumenta Formation, SMAF Santa Maria Ammalati Formation. Creep zone: CSC S. Caterina, TAAcireale Terme, BSC S. Caterina’ Belvedere (modified from Barbano et al., 2014).