Publication Date:
2021-02-25
Description:
There is growing interest in how geofluid emissions are released in the atmosphere by the
planet’s geodynamic activity, and how much they contribute to the global budget of
greenhouse gases. Many workers are addressing this issue with studies conducted at
global scale, so as to get the required global-scale answers. The data available at the global
scale on geofluids, faults, earthquakes and volcanoes, however, are generally too coarse
to provide these answers. We investigate the relationships between geofluid emissions
and tectonics at a more detailed scale. Building on over a century of data on geofluid
emissions and on an extensive knowledge of the region’s tectonics and seismicity, we
focused on Italy, one of the areas of the globe that experience the largest release of natural
CO2 and CH4. We systematically overlaid and compared data collected by a number of
workers into 13 published countrywide databases concerning geofluid emissions, carbonbearing
deposits, seismogenic faults, historical and instrumentally documented
earthquakes, and heat flow observations. Our results indicate that 1) thermal springs
and CO2 emissions dominate in areas of mantle upwelling and crustal stretching, but also
that 2) some of them occur in the extending inner Apennines, generally along major
lithospheric chain-perpendicular lineaments that bound the largest normal faults.
Conversely, 3) CH4 emissions and mud volcanoes dominate in areas undergoing
active contraction, where no CO2 emissions are observed; in particular, we find 4) that
mud volcanoes concentrate where the crests of active anticlines intersect major
lithospheric chain-perpendicular lineaments. An overarching conclusion is that, in Italy,
the release of geofluids is primarily controlled by deep crustal discontinuities that
developed over the course of 5–10 My, and is only mildly affected by ongoing crustal
strains. Geofluid emissions bring information on processes that occur primarily in the lower
crust, marking the surface projection of generally hidden discontinuities that control the
geometry and modes of seismic release. As such they may also provide valuable insight for
improving the assessment of seismic hazard in hard-to-investigate seismically active
regions, such as Italy.
Description:
Published
Description:
579390
Description:
7T. Variazioni delle caratteristiche crostali e precursori sismici
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article