GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 What does the seismic record of a World War II bomb-explosion look like? observatons from a controlled detonaton in 26 november 2023 near Ferrara, Italy Authors: F. Brighent 1 , A. Garcia 2 , R. Caputo 1 1 Dipartmento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Italy 2 Isttuto Nazionale di Geofsica e Vulcanologia, Sezione di Bologna, Bologna, Italy During restoraton operatons at the former Convent of San Benedeto in Corso Porta Po, in Ferrara (Italy), an unexploded aeroplane bomb from War World II (WWII) was found on the frst foor of the church (see e.g., press release from the Prefecture (Prefetura - Ufcio territoriale del Governo di Ferrara 2023). In the morning of 26 November 2023 the bomb was removed from this locaton and later, at 14:19 (UTC), a controlled detonaton of the war device was performed in a cave about 7 km NW of the city. The cave where the explosion occurred is located in an area in which a local seismic monitoring network, the SNet4Fer 3.0, operates for monitoring microseismicity around the Casaglia geothermal feld (Fig. 1). SNet4Fer 3.0 is an evoluton of the previous SNet4Fer 2.0 network, which is stll in operaton, and represents an improvement of the monitoring capabilites of the anthropogenic actvites that can potentally induce seismicity in the geothermal feld (Abu Zeid et al., 2017). Both networks are operated by the University of Ferrara. The NetFer 3.0 network consists of 7 seismic statons, each equipped with a surface accelerometer and a three-component, 2 Hz borehole seismometer (with the excepton of staton FEM0, which has a broadband borehole seismometer), all located 148 m below ground level. In additon, the NetFer 2.0 network consists of fve statons equipped with single-component (with the excepton of the PONT staton, which has a three-component instrument) borehole seismometers located at depths ranging from 12 to 57 m below ground level. Figure 2 shows some examples of the seismic records of the bomb explosion; in the records it is possible to distnguish relatvely, weak P and S phase arrivals as well as the seismic trace of the airwave from the airblast. Despite the energy of the explosions being relatvely low, if compared to earthquakes, the records in the nearby statons can provide interestng data for diferent analyses as e.g., for studying the anatomy of the records, for performing forensic analyses related with the equivalent charge of the war device, and also for checking the installaton of the borehole instrumentaton. In this work, we present some preliminary analyses of the seismic records of this explosion.