Publication Date:
2017-04-04
Description:
Cold CO2 gas emission sites in rainwater-filled pools, so called mofettes, are widely distributed
all over Italy. Their gas reservoirs, mostly having a high CO2 content, have a magmatic and/or
metamorphic origin. Temporal variations in fluid expulsions were observed at the mofettes of
Caprese Michelangelo during the period from 2002 to 2005. These observations were made
possible by using a new approach: photographic time-series. A first interpretation of these fluid
expulsionswas based on meteorological/hydrogeological explanations.However, our long-term
observations show that these processes may merely be a side effect. The probable main reason
for the anomalous emissions is the long-term variation in the long-distance fluid transport
process from the reservoir induced by the local tectonic settings. In the northern part of the
Alto Tiberina Fault, a fault intersection was reactivated by a seismic sequence which started on
2001 November 26, and continued for approximately four months. The magnitude of the main
shock was MW = 4.6. As revealed by the drilling of a deep borehole, dug in the direct vicinity,
overpressurized fluids trapped at a depth of 3700 m could be activated as a consequence of
the improved transport conditions, that is, the fracture apertures that materialized as a result
of the rupture process. A migration of the hypocentres towards the surface provides hints of
a possible pore pressure diffusion process. The consequence is an increased fluid transport to
the mofettes. The first indications of anomalous fluid expulsions at the mofettes of Caprese
Michelangelo were detected 18 months after the seismic events.
Description:
Published
Description:
974-806
Description:
reserved
Keywords:
earthquakes
;
fluid dynamics
;
hydrodynamics
;
microearthquakes
;
pore pressure diffusion
;
seismotectonics
;
04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
992000 bytes
Format:
application/pdf
