Evidence of poro-elastic inflation at the onset of the 2021 Vulcano Island (Italy) unrest

Thermal and pore-pressure variations induced by the circulation of hydrothermal-magmatic fluids in porous and permeable media contribute to ground deformation in volcanic areas. Here, we use solutions for the calculation of the displacements induced by pore-pressure and temperature changes for simplified geometry sources embedded in an elastic half-space with homogeneous mechanical and porous properties. The analytical solution for a spherical source is reviewed, and a semi-analytical approach for the calculation of the displacement for a cylindrical source is presented. Both models were used for the inversion of the daily deformation data recorded on Vulcano Island (Italy) during the 2021 unrest. Starting from September 2021, Vulcano Island experienced an increase in gas emission, seismic activity, and edifice inflation. The deformation pattern evolution from September until mid-October 2021 is indicative of a spatially stationary source. The modeling of the persistent and continuous edifice inflation suggests a deformation source located below the La Fossa crater at a depth of approximately 800 m from the ground surface undergoing a volume change of approximately 105 m3, linked to the rise in fluids from a deeper magmatic source. Corroborated by other sources of geophysical and geochemical evidence, the modeling results support that thermo-poro-elastic processes are sufficient to explain the observed displacement without necessarily invoking the migration of magma to shallow levels. Our findings demonstrate that thermo-poro-elastic solutions may help interpret ground deformation and gain insights into the evolution of the hydrothermal systems, providing useful implications for hazard assessment during volcanic crises.

This research was supported by the projects Pianeta Dinamico—WUnderVul (code CUP D53J1900010001) funded by MUR (Fondo Finalizzato al rilancio degli investimenti delle amministrazioni centrali dello Stato e allo sviluppo del Paese, legge 145/2018).

Acocella, V., Di Lorenzo, R., Newhall, C., and Scandone, R. (2015). An overview of recent (1988 to 2014) caldera unrest: knowledge and perspectives. Rev. Geophys. 53 (3), 896–955. doi:10.1002/2015RG000492

Aiuppa, A., Bitetto, M., Calabrese, S., Delle Donne, D., Lages, J., La Monica, F. P., et al. (2022). Mafic magma feeds degassing unrest at Vulcano Island, Italy. Commun. EARTH Environ. 3 (1), 255. doi:10.1038/s43247-022-00589-1

Alparone, S., Cannata, A., Gambino, S., Gresta, S., Milluzzo, V., and Montalto, P. (2010). Time-space variation of volcano-seismic events at La Fossa (vulcano, aeolian islands, Italy): new insights into seismic sources in a hydrothermal system. Bull. Volcanol. 72, 803–816. doi:10.1007/s00445-010-0367-6

Barbano, S., Castelli, V., and Pirrotta, C. (2017). Materiali per un catalogo di eruzioni di Vulcano e di terremoti delle isole Eolie e della Sicilia nordorientale (secc. XV-XIX). Quad. Geofis. 142. ISSN 1590-2595.

Barbot, S. (2018). Deformation of a half-space from anelastic strain confined in a tetrahedral volume. Bull. Seism. Soc. Am. 108 (5A), 2687–2712. doi:10.1785/0120180058

Battaglia, S., Gherardi, F., Gianelli, G., Leoni, L., and Origlia, F. (2007). Clay mineral reactions in an active geothermal area (Mt. Amiata, southern Tuscany, Italy). Clay Miner. 42 (3), 353–372. doi:10.1180/claymin.2007.042.3.08

Battaglia, M., Gottsmann, J., Carbone, D., and Fernández, J. (2008). 4D volcano gravimetry. Geophysics 73, WA3–WA18. doi:10.1190/1.2977792

Belardinelli, M. E., Bonafede, M., and Nespoli, M. (2019). Stress heterogeneities and failure mechanisms induced by temperature and pore-pressure increase in volcanic regions. Earth Planet. Sci. Lett. 525, 115765. doi:10.1016/j.epsl.2019.115765

Belardinelli, M. E., Nespoli, M., and Bonafede, M. (2022). Stress changes caused by exsolution of magmatic fluids within an axisymmetric inclusion. Geophys. J. Int. 230 (2), 870–892. doi:10.1093/gji/ggac093

Berrino, G. (2000). Combined gravimetry in the observation of volcanic processes in Southern Italy. J. Geodyn. 30 (3), 371–388. doi:10.1016/S0264-3707(99)00072-1

Bertiger, W., Bar-Sever, Y. E., Dorsey, A., Haines, B., Harvey, N., Hemberger, D., et al. (2020). GipsyX/RTGx, a new tool set for space geodetic operations and research. Adv. Space Res. 66 (3), 469–489. doi:10.1016/j.asr.2020.04.015

Blakely, R. J. (1996). Potential theory in gravity and magnetic Applications. Cambridge: Cambridge University Press, 437.

Bonafede, M. (1990). Axi-symmetric deformation of a thermo-poro-elastic half-space: inflation of a magma chamber. Geophys. J. Int. 103 (2), 289–299. doi:10.1111/j.1365-246X.1990.tb01772.x

Bonafede, M. (1991). Hot fluid migration: an efficient source of ground deformation: application to the 1982–1985 crisis at Campi Flegrei-Italy. J. Volcanol. Geotherm. Res. 48 (1-2), 187–198. doi:10.1016/0377-0273(91)90042-X

Cannata, A., Diliberto, I. S., Alparone, S., Gambino, S., Gresta, S., Liotta, M., et al. (2012). Multiparametric approach in investigating volcano-hydrothermal systems: the case study of vulcano (aeolian islands, Italy). Pure Appl. Geophys. 169, 167–182. doi:10.1007/s00024-011-0297-z

Capasso, G., Favara, R., Francofonte, S., and Inguaggiato, S. (1999). Chemical and isotopic variations in fumarolic discharge and thermal waters at vulcano island (aeolian islands, Italy) during 1996: evidence of resumed volcanic activity. J. Volcanol. Geotherm. Res. 88 (3), 167–175. doi:10.1016/S0377-0273(98)00111-5

Carapezza, M., Nuccio, P. M., and Valenza, M. (1981). Genesis and evolution of the fumaroles of vulcano (aeolian islands, Italy): A geochemical model. Bull. Volcanol. 44, 547–563. doi:10.1007/BF02600585

Carbone, D., Currenti, G., and Del Negro, C. (2008). Multiobjective genetic algorithm inversion of ground deformation and gravity changes spanning the 1981 eruption of Etna volcano. J. Geophys. Res. 113, B07406. doi:10.1029/2006JB004917

Chiarabba, C., Pino, N. A., Ventura, G., and Vilardo, G. (2004). Structural features of the shallow plumbing system of Vulcano Island Italy. Bul.l Volcanol. 66, 477–484. doi:10.1007/s00445-003-0331-9

Chiodini, G., Cioni, R., Falsaperla, S., Montalto, A., Guidi, M., and Marini, L. (1992). Geochemical and seismological investigations at vulcano (aeolian islands) during 1978–1989. J. Geophys. Res. 97 (B7), 11025–11032. doi:10.1029/92JB00518

Chiodini, G., Todesco, M., Caliro, S., Del Gaudio, C., Macedonio, G., and Russo, M. (2003). Magma degassing as a trigger of bradyseismic events: the case of phlegrean fields (Italy). Geophys. Res. Lett. 30 (8). doi:10.1029/2002GL016790

Coco, A., Gottsmann, J., Whitaker, F., Rust, A., Currenti, G., Jasim, A., et al. (2016). Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of a restless caldera. Solid Earth 7 (2), 557–577. doi:10.5194/se-7-557-2016

COMSOL (2012). Comsol Multiphysics 4,3. Stockholm: Comsol Ab.

Conca, P., Currenti, G., Carapezza, G., Del Negro, C., Costanza, J., and Nicosia, G. (2016). “Multi-objective modeling of ground deformation and gravity changes of volcanic eruptions,” in Machine learning, optimization, and big data. MOD 2015. Lecture notes in computer science. Editors P. Pardalos, M. Pavone, G. Farinella, and V. Cutello (Cham: Springer), Vol 9432. doi:10.1007/978-3-319-27926-8_32

Currenti, G. M., and Napoli, R. (2017). Learning about hydrothermal volcanic activity by modeling induced geophysical changes. Front. Earth Sci. 5 (41). doi:10.3389/feart.2017.00041

Currenti, G., Del Negro, C., and Nunnari, G. (2005). Inverse modelling of volcanomagnetic fields using a genetic algorithm technique. Geophys. J. Int. 163 (1), 403–418. doi:10.1111/j.1365-246X.2005.02730.x

Currenti, G., Del Negro, C., Fortuna, L., and Gangi, G. (2007). Integrated inversion of ground deformation and magnetic data at Etna volcano using a genetic algorithm technique. Ann. Geophys. 50 (1), 21–30. doi:10.4401/ag-3082

Currenti, G., Del Negro, C., Ganci, G., and Williams, C. (2008). Static stress changes induced by the magmatic intrusions during the 2002-2003 Etna eruption. J. Geophys. Res. 113, B10206. doi:10.1029/2007JB005301

Currenti, G., Napoli, R., Di Stefano, A., Greco, F., and Del Negro, C. (2011). 3D integrated geophysical modeling for the 2008 magma intrusion at etna: constraints on rheology and dike overpressure. Phys. Earth Planet. Inter. 168, 44–52. doi:10.1016/j.pepi.2011.01.002

Currenti, G., Napoli, R., Coco, A., and Privitera, E. (2017). Effects of hydrothermal unrest on stress and deformation: insights from numerical modeling and application to vulcano island (Italy). Bull. Volcanol. 79, 28. doi:10.1007/s00445-017-1110-3

Currenti, G., Allegra, M., Cannavò, F., Jousset, P., Prestifilippo, M., Napoli, R., et al. (2023). Distributed dynamic strain sensing of very long period and long period events on telecom fiber-optic cables at Vulcano, Italy. Sci. Rep. 13, 4641. doi:10.1038/s41598-023-31779-2

Davies, J. H. (2003). Elastic field in a semi-infinite solid due to thermal expansion or a coherently misfitting inclusion. J. Appl. Mech. 70 (5), 655–660. doi:10.1115/1.1602481

De Astis, G., Lucchi, F., Dellino, P., La Volpe, L., Tranne, C. A., Frezzotti, M. L., et al. (2013). Chapter 11 Geology, volcanic history and petrology of Vulcano (central Aeolian archipelago). Geol. Soc. Lond. Mem. 37, 281–349. doi:10.1144/M37.11

Diliberto, I. S. (2017). Long-term monitoring on a closed-conduit volcano: A 25 year long time-series of temperatures recorded at La Fossa cone (vulcano island, Italy), ranging from 250 °C to 520 °C. J. Volcanol. Geotherm. Res. 346, 151–160. doi:10.1016/j.jvolgeores.2017.03.005

Dzurisin, D. (2007). Volcano deformation – geodetic monitoring techniques. Chichester: Springer-Praxis Publishing Ltd.

Federico, C., Cocina, O., Gambino, S., Paonita, A., Branca, S., Coltelli, M., et al. (2023). Inferences on the 2021 ongoing volcanic unrest at vulcano island (Italy) through a comprehensive multidisciplinary surveillance network. Remote Sens. 15, 1405. doi:10.3390/rs15051405

Feng, K., Lu, Z., and Yang, C. (2019). Enhanced Morris method for global sensitivity analysis: good proxy of sobol’ index. Struct. Multidiscip. Optim. 59, 373–387. doi:10.1007/s00158-018-2071-7

Fournier, N., and Chardot, L. (2012). Understanding volcano-Hydrothermal unrest from geodetic observations: insights from numerical modeling and application to white island volcano, New Zealand. JGR 117, B11208. doi:10.1029/2012JB009469

Fung, Y. (1965). Foundations of solid mechanics. Englewood Cliffs, NJ: Prentice-Hall.

Gambino, S., and Guglielmino, F. (2008). Ground deformation induced by geothermal processes: A model for La Fossa crater (vulcano island, Italy). J. Geophys. Res. 113, B07402. doi:10.1029/2007JB005016

Goodier, J. N. (1937). “XCVII. On the integration of the thermo-elastic equations,” in The London, Edinburgh, and Dublin philosophical magazine and journal of science, series 7, 1017–1032. doi:10.1080/14786443708561872

Guglielmino, F., Bonforte, A., and Puglisi, G. (2022). “The 2021 unrest phase of Vulcano volcano (Aeolian islands) detected by SAR, GNSS and GB-RAR,” in EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022. EGU22-12183. doi:10.5194/egusphere-egu22-12183

Harris, A., Alparone, S., Bonforte, A., Dehn, J., Gambino, S., Lodato, L., et al. (2012). Vent temperature trends at the vulcano Fossa fumarole field: the role of permeability. Bull. Volcanol. 74, 1293–1311. doi:10.1007/s00445-012-0593-1

Heap, M. J., Baud, P., Meredith, P. G., Vinciguerra, S., and Reuschlé, T. (2014). The permeability and elastic moduli of tuff from Campi Flegrei, Italy: implications for ground deformation modelling. Solid Earth 5 (1), 25–44. doi:10.5194/se-5-25-2014

Hemmings, B., Gottsmann, J., Whitaker, F., and Coco, A. (2016). Investigating hydrological contributions to volcano monitoring signals: A time-lapse gravity example. Geophys. J. Int. 207 (1), 259–273. doi:10.1093/gji/ggw266

Hurwitz, S., Christiansen, L. B., and Hsieh, P. A. (2007). Hydrothermal fluid flow and deformation in large calderas: inferences from numerical simulations. J. Geophys. Res. 112, B02206. doi:10.1029/2006JB004689

Hutnak, M., Hurwitz, S., Ingebritsen, S. E., and Hsieh, P. A. (2009). Numerical models of caldera deformation: effects of multiphase and multicomponent hydrothermal fluid flow. J. Geophys. Res. 114, B04411. doi:10.1029/2008JB006151

Inguaggiato, S., Vita, F., Diliberto, I., Mazot, A., Calderone, L., Mastrolia, A., et al. (2022). The extensive parameters as a tool to monitoring the volcanic activity: the case study of vulcano island (Italy). Remote Sens. 14 (5), 1283. doi:10.3390/rs14051283

INGV Report (2022). Tutti i bollettini precedenti al 2018 è possibile trovarli sul vecchio portale di sezione. Available at: https://www.ct.ingv.it/index.php/monitoraggio-e-sorveglianza/prodotti-del-monitoraggio/bollettini-settimanali-multidisciplinari.

Jaeger, J., Cook, N., and Zimmerman, R. (2007). Fundamentals of rock mechanics 4th Edn. Oxford: Blackwell Publishing.

Juncu, D., Árnadóttir, Th., Geirsson, H., and Gunnarsson, G. (2019). The effect of fluid compressibility and elastic rock properties on deformation of geothermal reservoirs. Geophys. J. Int. 217 (1), 122–134. doi:10.1093/gji/ggz011

Keller, J. (1980). The island of Vulcano. Rend. Soc. Ital. Mineral. Petrol. 36, 369–414.

Kobayashi, T., Morishita, Y., and Munekane, H. (2018). First detection of precursory ground inflation of a small phreatic eruption by InSAR. Earth Planet. Sci. Lett. 491, 244–254. doi:10.1016/j.epsl.2018.03.041

Liu, D., Li, L., Rostami-Hodjegan, A., Bois, F. Y., and Jamei, M. (2020). Considerations and caveats when applying global sensitivity analysis methods to physiologically based pharmacokinetic models. AAPS J. 22, 93. doi:10.1208/s12248-020-00480-x

Lu, Z., Masterlark, T., Power, J., Dzurisin, D., and Wicks, C. (2002). Subsidence at kiska volcano, western aleutians, detected by satellite radar interferometry. Geophys. Res. Lett. 29 (18), 2-1–2-4. doi:10.1029/2002GL014948

Mantiloni, L., Nespoli, M., Belardinelli, M. E., and Bonafede, M. (2020). Deformation and stress in hydrothermal regions: the case of a disk-shaped inclusion in a half-space. J. Volcanol. Geotherm. Res. 403, 107011. doi:10.1016/j.jvolgeores.2020.107011

McTigue, D. F. (1986). Thermoelastic response of fluid-saturated porous rock. J. Geophys. Res. Solid Earth 91 (B9), 9533–9542. doi:10.1029/JB091iB09p09533

Miller, C. A., Le Mével, H., Currenti, G., Williams-Jones, G., and Tikoff, B. (2017). Microgravity changes at the laguna del maule volcanic field: magma-induced stress changes facilitate mass addition. J. Geophys. Res. 122 (4), 3179–3196. doi:10.1002/2017JB014048

Milluzzo, V., Cannata, A., Alparone, S., Gambino, S., Hellweg, M., Montalto, P., et al. (2010). Tornillos at vulcano: clues to the dynamics of the hydrothermal system. J. Volcanol. Geotherm. Res. 198 (3–4), 377–393. doi:10.1016/j.jvolgeores.2010.09.022

Mindlin, R. D., and Cheng, D. H. (1950). Nuclei of strain in the semi-infinite solid. J. Appl. Phys. 21 (9), 926–930. doi:10.1063/1.1699785

Mindlin, R. D. (1936). Force at a point in the interior of a semi-infinite solid. Physics 7 (5), 195–202. doi:10.1063/1.1745385

Mogi, K. (1958). Relation between eruptions of various volcanoes and the deformations of the ground surfaces around them. Bull. Earthq. Res. Inst. 36, 99–134.

Morris, M. D. (1991). Factorial sampling plans for preliminary computational experiments. Technometrics 33 (2), 161–174. doi:10.1080/00401706.1991.10484804

Na, S. H., Rim, H., Shin, Y. H., Lim, M., and Park, Y. S. (2015). Calculation of gravity due to a vertical cylinder using a spherical harmonic series and numerical integration. Explor. Geophys. 46 (4), 381–386. doi:10.1071/EG14123

Napoli, R., and Currenti, G. (2016). Reconstructing the Vulcano Island evolution from 3D modeling of magnetic signatures. J. Volcanol. Geother. Res. 320, 40–49. doi:10.1016/j.jvolgeores.2016.04.011

Napoli, R., Currenti, G., Del Negro, C., Greco, F., and Scandura, D. (2008). Volcanomagnetic evidence of the magmatic intrusion on 13th May 2008 Etnaeruption. Geophys. Res. Lett. 35, L22301. doi:10.1029/2008GL035350

Napoli, R., Currenti, G., Del Negro, C., Di Stefano, A., Greco, F., and Boschi, E. (2011). Magnetic features of the magmatic intrusion that occurred in the 2007 eruption at Stromboli Island (Italy). Bull. Volcanol. 73, 1311–1322. doi:10.1007/s00445-011-0473-0

Narita, S., Ozawa, T., Aoki, Y., Shimada, M., Furuya, M., Takada, Y., et al. (2020). Precursory ground deformation of the 2018 phreatic eruption on Iwo-Yama volcano, revealed by four-dimensional joint analysis of airborne and spaceborne InSAR. Earth, Planets Space 72, 145. doi:10.1186/s40623-020-01280-5

Nespoli, M., Belardinelli, M. E., and Bonafede, M. (2021). Stress and deformation induced in layered media by cylindrical thermo-poro-elastic sources: an application to Campi Flegrei (Italy). J. Volc. Geotherm. Res. 415, 107269. doi:10.1016/j.jvolgeores.2021.107269

Nespoli, M., Belardinelli, M. E., Cal, M., Tramelli, A., and Bonafede, M. (2022). Deformation induced by distributions of single forces in a layered half-space: EFGRN/EFCMP. Comput. Geosci. 164, 105136. doi:10.1016/j.cageo.2022.105136

Newhall, C. G., and Dzurisin, D. (1988). Historical unrest at large calderas of the world. Bullettin 1855. doi:10.3133/b1855

Phillipson, G., Sobradelo, R., and Gottsmann, J. (2013). Global volcanic unrest in the 21st century: an analysis of the first decade. J. Volcanol. Geotherm. Res. 264, 183–196. doi:10.1016/j.jvolgeores.2013.08.004

Rinaldi, A. P., Todesco, M., and Bonafede, M. (2010). Hydrothermal instability and ground displacement at the Campi Flegrei caldera. Phys. Earth Planet. Interiors 178 (3-4), 155–161. doi:10.1016/j.pepi.2009.09.005

Rinaldi, A. P., Todesco, M., Vandemeulebrouck, J., Revil, A., and Bonafede, M. (2011). Electrical conductivity, ground displacement, gravity changes, and gas flow at solfatara crater (Campi Flegrei caldera, Italy): results from numerical modeling. J. Volcanol. Geother. Res. 207 (3-4), 93–105. doi:10.1016/j.jvolgeores.2011.07.008

Ruch, J., Vezzoli, L., De Rosa, R., Di Lorenzo, R., and Acocella, V. (2016). Magmatic control along a strike-slip volcanic arc: the central aeolian arc (Italy). Tectonics 35 (2), 407–424. doi:10.1002/2015TC004060

Sambridge, M. (1999). Geophysical inversion with a neighbourhood algorithm: II. Appraising the ensemble. Geophys. J. Int. 138 (3), 727–746. doi:10.1046/j.1365-246x.1999.00900.x

Selva, J., Bonadonna, C., Branca, S., De Astis, G., Gambino, S., Paonita, A., et al. (2020). Multiple hazards and paths to eruptions: A review of the volcanic system of vulcano (aeolian islands, Italy). Earth Sci. Rev. 207, 103186. doi:10.1016/j.earscirev.2020.103186

Shapiro, S. A. (2015). Fluid-induced seismicity. Cambridge University Press. doi:10.1017/CBO9781139051132

Sternberg, E., and McDowell, E. L. (1957). On the steady-state thermoelastic problem for the half-space. Qu. Appl. Math. 14, 381.

Stissi, S. C., Napoli, R., Currenti, G., Afanasyev, A., and Montegrossi, G. (2021). Influence of permeability on the hydrothermal system at vulcano island (Italy): inferences from numerical simulations. Earth, Planets Space 73, 179. doi:10.1186/s40623-021-01515-z

Telford, W. M., Geldart, L. P., Sheriff, R. E., and Keys, D. A. (1981). Applied geophysics. Cambridge, New York, U.S.A.

Tiampo, K. F., Rundle, J. B., Fernandez, J., and Langbein, J. O. (2000). Spherical and ellipsoidal volcanic sources at Long Valley caldera, California, using a genetic algorithm inversion technique. J. Volcan. Geotherm. Res. 102 (3-4), 189–206. doi:10.1016/S0377-0273(00)00185-2

Todesco, M., Rinaldi, A. P., and Bonafede, M. (2010). Modeling of unrest signals in heterogeneous hydrothermal systems. J. Geophys. Res. 115, B09213. doi:10.1029/2010JB007474

CrossRef Full Text | Google Scholar

Todesco, M. (2021). Caldera’s breathing: poroelastic ground deformation at Campi Flegrei (Italy). Front. Earth Sci. 9, 70266. doi:10.3389/feart.2021.702665

Troiano, A., Di Giuseppe, M., Petrillo, Z., Troise, C., and De Natale, G. (2011). Ground deformation at calderas driven by fluid injection: modelling unrest episodes at Campi Flegrei (Italy): ground deformation driven by fluid injection. Geophys. J. Int. 187 (2), 833–847. doi:10.1111/j.1365-246X.2011.05149.x

Wang, H. F. (2000). Theory of linear poroelasticity with Applications to Geomechanics and hydrogeology. Princeton University Press.

Yunjun, Z., Amelung, F., and Aoki, Y. (2021). Imaging the hydrothermal system of kirishima volcanic complex with L-band InSAR time series. Geophys. Res. Lett. 48 (11), e2021GL092879. doi:10.1029/2021GL092879