- 1Dipartimento di Scienze Fisiche, della Terra e dell'Ambiente, Università degli Studi di Siena, Siena, Italy (albachiara.brindi@student.unisi.it, nicolo.carfagna@student.unisi.it, dario.albarello@unisi.it)
- 2Museo Nazionale dell’Antartide “Felice Ippolito”, Università degli Studi di Siena, Siena, Italy (albachiara.brindi@student.unisi.it)
- 3Dipartimento di Fisica ed Astronomia, Università degli Studi di Bologna, Bologna, Italy (enrico.paolucci3@unibo.it)
- 4Consiglio Nazionale delle Ricerche, Istituto di Geologia Ambientale e Geoingegneria, Rome, Italy (dario.albarello@unisi.it)
The presence of a minimum within the low-frequency range in the average Horizontal (H) to Vertical (V) Spectral Ratios of ambient vibrations has been suggested to be representative of hydrocarbon reservoirs in active oil and gas fields in the Middle East and Europe. Similar evidence has been also found in correspondence of active mud volcanoes in Italy (Antunes et al., 2022; Panzera et al., 2016). In this view, the aim of the study is to explore the possibility of using ambient vibrations to identify and characterize reservoir corresponding to mud volcanoes vents in the Nirano mud volcanoes area (Norther Italy). Seismic surveys carried out in the area so far allowed the seismic characterization of the shallowest part of the subsoil involved in the emission process (Antunes et al., 2022; Brindisi et al., 2023; Carfagna et al., 2024). To extend downward this characterization and understand if the presence of the minimum detected in the Nirano Reserve (Antunes et al., 2022) is confined to the area of emitting vents, an extensive survey of ambient vibrations was performed. In particular, a dense network of velocimetric measurements has been deployed by considering single station and array configurations. Results obtained confirm that measurements with a clear HVSR minimum at around 0.5 Hz only characterize the area of emitting vents. In the assumption that this minimum depends on the characteristics of the reservoir responsible for fluid emissions, the Biot–Gassmann theory (Lee, 2004; Tinivella, 2002) for seismic waves velocities of gas hydrate-bearing sediments has been considered to infer reservoir characteristics from Vs and Vp profiles obtained by the inversion of the HVSR curves. The satisfactory fit of model outcomes with observations testifies one more the effectiveness of ambient vibration measurements to characterize mud volcanoes and relevant subsoil configuration. This opens new possibilities for the study of mud volcanoes and gas reservoirs both onshore and offshore by passive seismic observations.
References
Antunes V., Planès T., Obermann A., Panzera F., D’Amico S., Mazzini A., Lupi M.; 2022: Insights into the dynamics of the Nirano Mud Volcano through seismic characterization of drumbeat signals and V/H analysis. J. Volcanol. Geoth. Res., 431, 107619. https://doi.org/10.1016/j.jvolgeores.2022.107619.
Brindisi A., Carfagna N., Paolucci E., Albarello D.; 2023: Fine structure of seismic emissions from Nirano mud volcanoes (northern Apennines, Italy): a phenomenological study. Bull. Geophys. Oceanogr, 20, 1-12. DOI 10.4430/bgo00437.
Carfagna N., Brindisi A., Paolucci E., Albarello D.; 2024: Seismic monitoring of gas emissions at mud volcanoes: The case of Nirano (northern Italy). J. Volcanol. Geotherm., 446, 107993. https://doi.org/10.1016/j.jvolgeores.2023.107993.
Lee M.W.; 2004: Elastic velocities of partially gas-saturated unconsolidated sediments. Mar. Pet. Geol., 21(6), 641-650. https://doi.org/10.1016/j.marpetgeo.2003.12.004.
Panzera F., Sicali S., Lombardo G., Imposa S., Gresta S., D’Amico S.; 2016: A microtremor survey to define the subsoil structure in a mud volcanoes area: the case study of Salinelle (Mt. Etna, Italy). Environ. Earth Sci., 75, 1-13. https://doi.org/10.1007/s12665-016-5974-x.
Tinivella U.; 2002: The seismic response to over-pressure versus gas hydrate and free gas concentration. J. Seism. Explor., 11(3), 283-305.
How to cite: Brindisi, A., Paolucci, E., Carfagna, N., and Albarello, D.: Passive seismic measurements to characterize gas reservoirs in a mud volcano field in Northern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10680, https://doi.org/10.5194/egusphere-egu25-10680, 2025.
