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| Titel |
Hydrogeochemical response of groundwater springs during central Italy earthquakes (24 August 2016 and 26-30 October 2016) |
| VerfasserIn |
Claire Archer, Gilberto Binda, Silvia Terrana, Roberto Gambillara, Alessandro Michetti, Paula Noble, Marco Petitta, Michael Rosen, Andrea Pozzi, Paolo Bellezza, Fabio Brunamonte |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139365
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| Publikation (Nr.) |
 EGU/EGU2017-2592.pdf |
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| Zusammenfassung |
| Co-seismic hydrological and chemical response at groundwater springs following strong
earthquakes is a significant concern in the Apennines, a region in central Italy characterized
by regional karstic groundwater systems interacting with active normal faults capable of
producing Mw 6.5 to 7.0 seismic events. These aquifers also provide water supply to major
metropolitan areas in the region.
On August 24, 2016, a Mw 6.0 earthquake hit Central Italy in the area where Latium joins
Umbria, Marche and Abruzzi; this was immediately followed one hour later by a Mw 5.4
shock. The epicenter of the event was located at the segment boundary between the Mt.
Vettore and Mt. Laga faults. On October 26, 2016 and on October 30, 2016, three other big
shocks (Mw 5.5, Mw 6.0 and Mw 6.5) ruptured again the Vettore Fault and its NW
extension.
Immediately after Aug. 24, we sampled springs discharging different aquifers in the Rieti
area, including the Peschiera spring, which feeds the aqueduct of Rome. Thermal springs
connected with deep groundwater flowpaths were also sampled. These springs, sampled
previously in 2014 and 2015, provide some pre-earthquake data. Moreover, we sampled 4
springs along the Mt. Vettore fault system: 3 small springs at Forca di Presta, close to the
trace of the earthquake surface ruptures, and two in Castel Sant’Angelo sul Nera.
The latter are feeding the Nera aqueduct and the Nerea S.p.A. mineral water plant,
which also kindly allowed us to collect bottled water samples from the pre-seismic
period.
The aim of this study is to evaluate the strong earthquake sequence effects on
the hydrochemistry and flow paths of groundwater from different aquifer settings
based on analysis before and after seismic events. The comparison between the
responses of springs ca. 40 km from the epicenter (Rieti basin) and the springs located
near the epicenter (Castelsantangelo sul Nera and Forca di Presta) is especially
significant for understanding the resilience of groundwater systems in an active
tectonic zone because these springs are located near parallel active fault segments
within the same extensional regime. The epicentral springs are subject to the direct
effects of the shaking and coseismic fault displacement; the more distal ones to the
tectonic displacement of large hydrogeologic structures, which affect the chemical
composition and flow path even with late responses, lasting for weeks and months after the
mainshocks.
Temporal trend analysis, based on pre-earthquake and post-earthquake chemical-physical
data, point out alteration of different parameters. For example, the lowering of different trace
metals in all areas after the first earthquake. These changes could be due to fluctuations in
redox equilibria related to degassing and/or interactions with deeper fluid flow. In the Rieti
springs, the EC, alkalinity, and trace metals show small transient responses within 1-3 days
following the main shocks, however δ2H vs. δ18O remain stable and plot with previous data,
indicating no major change in recharge source. Analysis is ongoing and preliminary results
will be presented here. |
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