Tectonic structures vs genesis and activity of mud volcanoes: examples from Emilia and Marche (Northern Apennines, Italy)

Mud volcanism is known to be strictly linked to anticlines, since these structures have the ability to trap hydrocarbons and other fluids into reservoirs placed at their core, where large overpressures may be generated. Despite mud volcanoes have been widely studied, a central and still debated theme is (i) how fluids are able to migrate upward bypassing the overburden and erupt at surface, and (ii) which role near-structures (i.e. structure directly linked to the mud volcano system, or located not far from it) and far-structures (i.e. faults located far away from the mud volcano system) may play in this process. In an effort to address these questions, we investigated the role of both types of structures in the genesis and evolution of mud volcanoes. In particular, we show six mud volcano case studies from the Emilia-Romagna and Marche pede-Apennine margin, in Italy. We integrated fieldwork data and interpretation of available seismic reflection profiles whit aerial photo analysis. Our results support the intimate link of the investigated mud volcano systems with anticline structures on top of which they are typically emplaced. We then discuss two distinct settings for fluid migration and mud volcano formation, particularly: (i) mud volcanoes emplaced on outcropping anticlines, and (ii) mud volcanoes located on top of buried structures, discerning when fluids are likely to exploit anticline-related fracture sets, or secondary structures and porosity. Finally, we speculate on how far-structures may still play a crucial role, via seismic triggering, in the occurrence of historical eruptions of some of the investigated mud volcano systems.