GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 3.1 479 Multichannel seismic study of the Gondola fault system (Adriatic sea) G. Aiello CNR IAMC Sede di Napoli, Italy Introduction. A seismic study of the Gondola fault system, located in the Southern Adriatic sea is herein presented based on multichannel seismic data (Zone D and Zone E) supplied by Italian Ministry of Industry, coupled with well lithostratigraphic data drilled in the same area and providing a good stratigraphic framework of the investigated area. The Gondola fault system has been previously studied in several papers on the Adriatic area (De Dominicis and Mazzoldi, 1987; Colantoni et al. , 1990; Aiello and de Alteriis, 1991; Aiello, 1992, 1993; de Alteriis and Aiello, 1993; Patacca and Scandone, 2004; Billi et al. , 2007; Argnani et al. , 2009; Di Bucci et al. , 2009; Dalla Valle et al. , 2015), showing its close relationships with fault systems located onshore in the Gargano Promontory (Billi et al. , 2007). New insights have been recently furnished on the palaeo-seismological meaning of the Gondola fault system in recasting historical earthquakes in coastal areas of Gargano Promontory based on marine palaeo-seismology based on high resolution seismic data (Subbottom Chirp; Di Bucci et al. , 2009; Fracassi et al. , 2012). The historical earthquakes of the northern sector of the southern Adriatic area have been often related to the activity of faults located onshore, such as the Mattinata fault, E-W trending and having both regional meaning and extension. Earthquakes are suggested to occur in correspondence to the Gondola fault zone, representing the offshore prolongation of the Mattinata fault and probably triggering historical earthquakes of the area, such as the seismic event of 1893 (Di Bucci et al. , 2009). The Gondola fault system is herein studied based on a dense seismic network of multichannel profiles (Fig. 1) provided by the Italian Ministry of Industry to put it in a regional geological context of southern Apennines and Apulia-Gargano foreland of the chain (Mostardini and Merlini, 1986; Casero et al. , 1988; Sella et al. , 1988; Patacca and Scandone, 1989; Marsella et al. , 1992; Ricchetti et al. , 1992). About 1500 km of multichannel seismic profiles have been interpreted pertaining to the Zone D and the Zone F. The Zone D survey has been acquired in the 1968 from the American company GSI, while the Zone F survey has been recorded in the 1976 from the French company CGG. Main parameters of acquisition and processing are herein indicated and shown: Zone D; GSI survey; source: dynamite-airgun; acquisition frequency: 8-75 kHz; coverage: 600-2400%; processing: stack-deconvolution; Zone F: CGG survey; source: vaporchoc; acquisition frequency: 8-125 Hz; coverage: 4800%; processing: stack-deconvolution. The lithostratigraphic data and the electric logs of the following deep exploration wells have been used, drilled in the Apulia offshore fromAGIP and other geophysical companies: Gargano Est-Marine 1, Gondola 1bis, Cigno Mare 1, Jolly 1, Giuliana 1, Grazia 1, Grifone 1, Rovesti 1; Imago 1, Picchio 1, Rosaria Mare 1, Sabrina 1, Branzino 1, Simona 1, Cristina 1, Sonia 1, Stella 1, Famoso 1 and Eterno 1. Some data will be furnished in the section on results. Geodynamical and geophysical setting. The whole geophysical data herein exposed (distribution of the Bouguer anomalies, thickness of the Pliocene cover in the Adriatic area, seismicity) have confirmed the occurrence to a regional scale of the Apulian block (the Apulian microplate), separating the system of Pliocene foredeeps of the Apennine, running from the Pescara offshore to the Bradanic foredeep and the Taranto Gulf from theMio-Pliocenic foredeep, located in the southern Adriatic offshore of Puglia since the Jugoslavia and the Albania and linked to the Dinaric-Hellenic chain. The gravimetric data interpretation has allowed to hypothesize for the Apulian area onshore average crustal thicknesses with a minimum of 25 km below the Gargano and a maximum of