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Solid Earth An interactive open-access journal of the European Geosciences Union
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Volume 7, issue 6
Solid Earth, 7, 1537-1549, 2016
https://doi.org/10.5194/se-7-1537-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Solid Earth, 7, 1537-1549, 2016
https://doi.org/10.5194/se-7-1537-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Nov 2016

Research article | 08 Nov 2016

On the mechanical behaviour of a low-angle normal fault: the Alto Tiberina fault (Northern Apennines, Italy) system case study

Luigi Vadacca1,2, Emanuele Casarotti2, Lauro Chiaraluce2, and Massimo Cocco2 Luigi Vadacca et al.
  • 1MOX, Dipartimento di Matematica “F. Brioschi”, Politecnico di Milano, Milan, Italy
  • 2Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy

Abstract. Geological and seismological observations have been used to parameterize 2-D numerical elastic models to simulate the interseismic deformation of a complex extensional fault system located in the Northern Apennines (Italy). The geological system is dominated by the presence of the Alto Tiberina fault (ATF), a large (60km along strike) low-angle normal fault dipping 20° in the brittle crust (0–15km).  The ATF is currently characterized by a high and constant rate of microseismic activity, and no moderate-to-large magnitude earthquakes have been associated with this fault in the past 1000 years. Modelling results have been compared with GPS data in order to understand the mechanical behaviour of this fault and a suite of minor syn- and antithetic normal fault segments located in the main fault hanging wall.

The results of the simulations demonstrate the active role played by the Alto Tiberina fault in accommodating the ongoing tectonic extension in this sector of the chain. The GPS velocity profile constructed through the fault system cannot be explained without including the ATF's contribution to deformation, indicating that this fault, although misoriented, has to be considered tectonically active and with a creeping behaviour below 5km depth.

The low-angle normal fault also shows a high degree of tectonic coupling with its main antithetic fault (the Gubbio fault), suggesting that creeping along the ATF may control the observed strain localization and the pattern of microseismic activity.

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