The alto Tiberina near fault observatory (northern Apennines, Italy)

The availability of multidisciplinary and high-resolution data is a fun- damental requirement to understand the physics of earthquakes and faulting. We present the Alto Tiberina Near Fault Observatory (TABOO), a research infrastructure devoted to studying preparatory processes, slow and fast deformation along a fault system located in the upper Tiber Val- ley (northern Apennines), dominated by a 60 km long low-angle normal fault (Alto Tiberina, ATF) active since the Quaternary. TABOO consists of 50 permanent seismic stations covering an area of 120 × 120 km2. The surface seismic stations are equipped with 3-components seismometers, one third of them hosting accelerometers. We instrumented three shallow (250 m) boreholes with seismometers, creating a 3-dimensional antenna for studying micro-earthquakes sources (detection threshold is ML 0.5) and detecting transient signals. 24 of these sites are equipped with con- tinuous geodetic GPS, forming two transects across the fault system. Geo- chemical and electromagnetic stations have been also deployed in the study area. In 36 months TABOO recorded 19,422 events with ML ≤ 3.8 corresponding to 23.36e-04 events per day per squared kilometres; one of the highest seismicity rate value observed in Italy. Seismicity distribution images the geometry of the ATF and its antithetic/synthetic structures lo- cated in the hanging-wall. TABOO can allow us to understand the seismo- genic potential of the ATF and therefore contribute to the seismic hazard assessment of the area. The collected information on the geometry and de- formation style of the fault will be used to elaborate ground shaking sce- narios adopting diverse slip distributions and rupture directivity models. © 2014 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.