Seismogenic-influenced fluid transport on low angle faults to the mofettes of Caprese Michelangelo (Northern Apennines)

Abstract

The reservoirs feeding those mofettes are trapped over-pressurized fluids, discovered by a deep borehole in the near vicinity. Chemical and isotope data of both the venting gases and gases from the drilled well provide indications about their origin. We discuss a fault-valve behavior during the rupture process as responsible mechanism for a co-seismic fluid migration along reactivated fractures zones. A migration of hypocenters towards the surface along the fault gives further indications for a pore pressure diffusion process. At the surface, the mofettes changed their morphological features macroscopically due to this enhanced gas dynamic. The phenomenological observation of post-seismic fluid expulsion 18 months after the seismic crisis suggests the interpretation of a long-term fluid transport process forced by pressure pulse propagation. This result was achieved by a new approach using photographical times series. The proposed model could help to explain a complex scenario of a long-term fluid transport from the trapped fluid reservoir through the seismogenic zone up to the gas emission sites at Caprese Michelangelo.