Impulsive ground movements in the mud volcanoes area of "le Sarse" di Puianello (Northern Apennines, Modena, Italy): Field evidence and multi-approach monitoring

In this contribution we present the work carried out to determine the nature of the impulsive vertical ground movements occurred in February 2015 in the mud-volcanoes area "Le Sarse" (Northern Apennines, Modena province, Italy). A multi-technique based work has been started including field surveys, SAR Multi-Interferometric processing and high-precision periodical D-GPS monitoring. Field evidence indicates that movements occurred in February 2015, in the order of 25 cm in few minutes, can be ascribed to a vertical collapse of part of the caldera area rather than to a landslide activity. The affected area is bordered by concentric normal faults that were originated during February 2015. According to SAR interferometry, the collapsed area was already undergoing movements in the order of 2 cm/year at least from 2012. The D-GPS monitoring indicates that movement rates have nowadays still taking place at rates higher than those of the pre-event. In conclusion, it can be assumed that movements in the area are most likely related to the mechanisms controlling the activity and evolution of the mud volcano itself. However, the reconstruction of the structural characteristics of this caldera system and the identification of the specific causes for the February 2015 event still need to be further investigated.