IRIS Unicas (Università degli Studi di Cassino e del Lazio Meridionale)

Granata, F.

Di Nunno, F.

Assessing atmospheric influences for improving time-varying data-driven decadal predictions of Mediterranean spring discharge

Spiridigliozzi, L.

Monfreda, V.

Dell'Agli, G.

Esposito, S.

Engineered synthesis of a novel bixbyite-structured high-entropy oxide (Ce0.2Zr0.2Yb0.2Er0.2Gd0.2)2O3.4 as a stable and high-performing visible-light-active photocatalyst for multifunctional pollutant degradation

Ciccodicola, Floriana

Antropologia storica

Cherti, Stefano

Contratti Bancari

Zullo, E.

Albano, M.

Saroli, M.

Testa, G.

Bonora, N.

Session  1.1                    GNGTS 2025
Conceptual and numerical analysis of 
hydrogeological changes in the Sibillini Mts. due 
to the Mw 6.5 Norcia earthquake 
E. Zullo1, M. Albano2, M. Saroli1, M. Moro2, G. Testa1, N. Bonora1, M. Pe'ca3, T. 
Reimann4, C. Doglioni3 
1 Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, 
Cassino (FR), Italy 
2 Na%onal Ins%tute of Geophysics and Volcanology, Rome, Italy 
3 Department of Earth Science, University “La Sapienza”, Rome, Italy 
4Ins%tute of Groundwater Management, TUDresden, Dresden, Germany 
Introduc'on 
Earthquakes are widely recognized for inducing varia<ons in hydrogeological systems. Within the 
field of earthquake hydrogeology, these varia<ons are consistently akributed to changes in crustal 
permeability, driven by the interplay of mul<ple mechanisms occurring within the crustal porous 
medium in response to seismic shaking and pore pressure varia<on (Manga & Wang, 2007; Wang 
& Manga, 2010) Such hydrogeological responses are typically observed at springs, along major 
rivers, and in wells, where they manifest primarily as anomalous varia<ons in discharge rates and 
fluctua<ons in piezometric levels. 
The Mw 6.5 Norcia earthquake, which occurred on October 30, during the well-known 2016 Central 
Italy seismic sequence (Chiaraluce et al. 2017), profoundly affected the regional hydrogeological 
system of the Sibillini Mts. Unlike the transient nature of most earthquake-induced 
hydrogeological changes, the effects of the Mw 6.5 mainshock have proven to be long-las<ng, with 
clear evidence s<ll observable today. 
This study aims to analyse the hydrogeological changes induced by the Mw 6.5 Norcia earthquake 
within the complex hydrogeological system of the Sibillini Mts., by using conceptual models and 
numerical analysis. Par<cular aken<on is given to the role of seismogenic and capable faults in the 
Sibillini area and how these structures influence the groundwater circula<on. 
Materials and Methods 
The extensive available documenta<on regarding the Norcia earthquake and the related effects, 
along with pre- and post-seismic hydrogeological monitoring data, were analysed to define a 
conceptual model. The data set include informa<on on seismic ac<vity, spring discharge rates and 
piezometric fluctua<ons, hydrogeochemical analysis and tracer test results, as well as geological 
and hydrogeological informa<on of the study area. Although the groundwater circula<on of the 
Sibillini Mts. hydrogeological system is compartmentalized within several hydrogeological 
Session  1.1                    GNGTS 2025
complexes, a single aquifer is assumed for the hydrostructure. The bokom of the aquifer was 
reconstructed by interpola<ng data from available hydrogeological cross-sec<ons (Viaroli et al. 
2021) and 3D geological informa<on (RETRACE-3D Working Group, 2021). Seismogenic faults in the 
area are considered as rela<ve hydrogeological barriers, influencing the groundwater flow 
differently in the pre- and post-seismic. A numerical analysis was then performed by using the 
MODFLOW-OWHM code (Hanson et al. 2014). The groundwater flow before and aaer the Norcia 
earthquake was simulated by adop<ng the equivalent porous medium approach to model the 
aquifer, and the Horizontal Flow Barrier package (Hsieh and Freckleton 1993) was used to model 
the seismogenic faults. A parameters calibra<on of the pre-seismic groundwater flow model was 
performed by using the PEST algorithm (Doherty, 2015). 
Results and future perspec'ves 
The comprehensive literature analysis enabled the reconstruc<on of a conceptual hydrogeological 
model of the Sibillini Mts. hydrostructure at a regional scale, encompassing the whole area where 
hydrogeological varia<ons were observed. The model extends to shallow crustal depths and is 
constrained by physical and hydraulic boundaries iden<fied in the study area. A 3D representa<on 
of the conceptual model is shown in Figure 1. Both the Vekore-Bove fault system (VBfs) and the 
Norcia fault system (Nfs) are implemented in the conceptualiza<on as simplified structures. 
 
 
Fig. 1 – Regional hydrogeological conceptual model, 3D geometric representa<on 
Session  1.1                    GNGTS 2025
Two groundwater flow model were developed based on the defined conceptualiza<on, whose 
simula<on results are shown in Figure 2(a, b). In the pre-seismic groundwater flow, both VBfs and 
Nfs act as rela<ve hydrogeological barriers. Their barrier effect leads to a differen<ated hydraulic 
head within the hydrostructure, decreasing from east to west. Calibra<on of the hydraulic 
parameters was performed by using measured heads and discharge rates as target observa<ons. 
The resul<ng parameteriza<on was then applied to simulate the groundwater flow in the post-
seismic scenario (Figure 2b). According to the concept of “Aquifer Fault Rupture” (Mastrorillo et al. 
2020), the Norcia earthquake was simulated by removing the barrier effect of the VBfs. This 
forward simula<on results in a redistribu<on of the hydraulic head in the model, especially to the 
east of the VBfs, and a subsequent change in spring discharge. 
 
Fig. 2 – Regional groundwater flow numerical models a) before and b) aaer the earthquake 
The results of this study are both qualita<ve and quan<ta<ve. The numerical models and the 
employed modelling approaches reproduce consistent scenarios, confirming the hypothesis that 
the faults act as rela<ve hydrogeological barriers. These findings provide valuable insights into the 
sustained hydrogeological varia<ons induced by the Mw 6.5 Norcia earthquake. Furthermore, the 
model’s ability to simulate both scenarios highlight the importance of a reliable hydrogeological 
conceptual model. 
Future research will focus on further refining the models and analysing groundwater flow in a 
transient simula<on to gain deeper insights into the func<oning of such a complex system and the 
non-transitory nature of the earthquake-induced hydrogeological changes. 
Session  1.1                    GNGTS 2025
References  
Chiaraluce L., Di Stefano R., Tin< E., Scognamiglio L., Michele M., Casarow E., Cakaneo M., De Gori 
P., Chiarabba C., Monachesi G., Lombardi A., Valoroso L., Latorre D., Marzora< S.; 2017. The 2016 
Central Italy Seismic Sequence: A First Look at the Mainshocks, Aaershocks, and Source Models. 
Seismological Research Lekers 88, 757–771. hkps://doi.org/10.1785/0220160221  
Doherty J.; 2015. Calibra<on and uncertainty analysis for complex environmental models. 
Watermark Numerical Compu<ng, Brisbane, Australia. 
Hanson R.T., Boyce Scok. E., Schmid W., Hughes J.D., Mehl S.M., Leake S.A., Maddok T.I., Niswonger 
R.G.; 2014. One-Water Hydrologic Flow Model (MODFLOW-OWHM): U.S. Geological Survey 
Techniques and Methods 6–A51 (Techniques and Methods), Techniques and Methods. 
Hsieh P.A., Freckleton J.R.; 1993. Documenta<on of a computer program to simulate horizontal-
flow barriers using the U.S. Geological Survey’s modular three-dimensional finite-difference 
ground-water flow model (USGS Numbered Series), Open-File Report. 
Manga M., Wang C.-Y.; 2007. 4.10 - Earthquake Hydrology, in: Trea<se on Geophysics. Elsevier, pp. 
293–320. 
Mastrorillo L., Saroli M., Viaroli S., Banzato F., Valigi D., Pe<ka M.; 2020. Sustained post-seismic 
effects on groundwater flow in fractured carbonate aquifers in Central Italy. Hydrological Processes 
34, 1167–1181. hkps://doi.org/10.1002/hyp.13662  
RETRACE-3D Working Group; 2021. Progeko RETRACE-3D - centRal italy EarThquakes integRAted 
Crustal modEl - Rapporto Finale. Zenodo. hkps://doi.org/10.5281/ZENODO.4604940 
Viaroli S., Mirabella F., Mastrorillo L., Angelini S., Valigi D.; 2021. Fractured carbonate aquifers of 
S ibi l l in i Mts. (Central I ta ly) . Journal of Maps 17, 140–149. hkps://doi .org /
10.1080/17445647.2021.1894252  
Wang C., Manga M.; 2010. Hydrologic responses to earthquakes and a general metric. Geofluids 
10, 206–216. hkps://doi.org/10.1111/j.1468-8123.2009.00270.x  
Corresponding author: enrica.zullo@unicas.it 


English

Conceptual and numerical analysis of hydrogeological changes in the Sibillini Mts. due to the Mw 6.5 Norcia earthquake

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Italian

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University of Cassino and Southern Lazio

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