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Faulting and Gas Discharge in the Rome Area (Central Italy) and Associated Hazards
Author(s) -
Carapezza M. L.,
Barberi F.,
Ranaldi M.,
Tarchini L.,
Pagliuca N. M.
Publication year - 2019
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2018tc005247
Subject(s) - geology , aquifer , mesozoic , natural gas , soil gas , submarine pipeline , isotopes of carbon , geochemistry , groundwater , geomorphology , total organic carbon , geotechnical engineering , structural basin , ecology , chemistry , organic chemistry , biology , soil science , soil water
The area of Central Italy around Rome contains natural gas discharging zones and several others where quarrying or mining excavation removed the impervious superficial layers allowing a free hazardous discharge to the surface of endogenous gas. These gas manifestations are mostly located above buried structural highs of fractured Mesozoic limestones hosting the main regional aquifer and revealed by gravity anomalies. In the last decades, many gas blowouts occurred in this area, from wells whose depth ranged from 10–15 to 350 m. The main component of the emitted gas is CO 2 with minor H 2 S; only in a blowout offshore of Fiumicino CH 4 prevailed. Several animals even of large size and two persons were killed by the emitted gas (mostly by H 2 S), and nearby houses were evacuated because of dangerous indoor CO 2 concentrations. He and CO 2 ‐carbon isotopes suggest that gas has a deep mantle signature, as indicated for Fiumicino gas by N 2 isotopic composition and N 2 / 36 Ar ratios. Gas rising from depth first accumulates in the buried Mesozoic limestone reservoir, and from there it escapes along deep‐reaching faults. On its way to the surface, the gas dissolves into and pressurizes any encountered confined aquifer, which may then produce a gas blowout when reached by wells. The main direction of the gas feeding faults was estimated through the alignment of visible gas emissive points, the shape of the positive anomalies in soil CO 2 flux maps, and new structural‐geological observations, finding that they correspond mostly to the main orientation of the underlying limestone structural high.