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www.nat-hazards-earth-syst-sci.net/3/269/2003/
doi:10.5194/nhess-3-269-2003
© Author(s) 2003. This work is licensed
under a Creative Commons License.
Thermal anomalies and fluid geochemistry framework in occurrence of the 2000-2001 Nizza Monferrate seismic sequence (northern Italy): Episodic changes in the fault zone heat flow or chemical mixing phenomena?
1INGV-Roma, Via di Vigna Murata 605, 00143 Roma, Italy
2INGV-Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italy
Abstract. The paper discusses the correlation between the heating of shallow groundwater over a 10 × 20 km wide area close to the town of Nizza Monferrato (Piemonte Region, Northern Italy) and the concomitant local seismic sequences during the period August 2000 – July 2001. The first seismic sequence started on 21 August 2000 with a Ml = 5.2 earthquake. Within few hours, the local authorities received calls alerting that the groundwater temperature rose from 10 to 30°C in many shallow wells. Our geochemical experimental data and the geological-seismotectonic framework do not allow the hypothesis of simple fluid mixing between the thermal reservoir of Acqui Terme and the Nizza-Monferrato shallow groundwater to explain the observed thermal anomalies. On the other hand, we invoke more complex processes such as frictional heating, mechano-chemistry, fault-valve mechanism, adiabatic decompression and hydrogeologically driven heat flow i.e., thermal effects due to variations of basin-scale permeability field. All these processes are able to transmit heat to the surface and to generate a transient incremental heat flow better than the mass transfer occurring typically when fluids from different reservoirs mix.
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Citation: Quattrocchi, F., Favara, R., Capasso, G., Pizzino, L., Bencini, R., Cinti, D., Galli, G., Grassa, F., Francofonte, S., and Volpicielli, G.: Thermal anomalies and fluid geochemistry framework in occurrence of the 2000-2001 Nizza Monferrate seismic sequence (northern Italy): Episodic changes in the fault zone heat flow or chemical mixing phenomena?, Nat. Hazards Earth Syst. Sci., 3, 269-277, doi:10.5194/nhess-3-269-2003, 2003. Bibtex EndNote Reference Manager XML
