New constraints on the shear wave velocity structure of the Ivrea geophysical body from seismic ambient noise tomography (Ivrea-Verbano Zone, Alps)

0584036 - GFÚ 2025 RIV GB eng J - Článek v odborném periodiku
Scarponi, Matteo - Kvapil, Jiří - Plomerová, Jaroslava - Solarino, S. - Hetényi, G.
New constraints on the shear wave velocity structure of the Ivrea geophysical body from seismic ambient noise tomography (Ivrea-Verbano Zone, Alps).
Geophysical Journal International. Roč. 236, č. 2 (2024), s. 1089-1105. ISSN 0956-540X. E-ISSN 1365-246X
Grant CEP: GA MŠMT(CZ) LM2015079; GA ČR(CZ) GA21-25710S
Institucionální podpora: RVO:67985530
Klíčová slova: continental crust * seismic noise * seismic tomography * continental tectonics * crustal structure
Obor OECD: Volcanology
Impakt faktor: 2.8, rok: 2022
Způsob publikování: Open access

We performed seismic ambient noise tomography to investigate the shallow crustal structure around the Ivrea geophysical body (IGB) in the Ivrea-Verbano Zone (IVZ). We achieved higher resolution with respect to pre vious tomo graphic works covering the Western Alps, by processing seismic data collected by both permanent and temporary seismic networks (61 broad-band seismic stations in total). This included IvreaArray, a temporary, passive seismic experiment designed to investigate the IVZ cr ustal str ucture. Star ting from continuous seismic ambient noise recordings, we measured and inverted the dispersion of the group velocity of surface Rayleigh waves (fundamental mode) in the period range 4–25 s. We obtained a new, 3-D v S model of the IVZ crust via the stochastic neighbourhood algorithm (NA), with the highest resolution between 3 to 40 km depth. The fast and shallow shear wave velocity anomaly associated with the IGB presents velocities of 3.6 km s −1 directly at the surface, in remarkable agreement with the location of the exposed lower-to-middle crustal and mantle outcrops. This suggests a continuity between the surface geological observations and the subsurface geophysical anomalies. The fast IGB structure reaches v S of 4 km s −1 at 20–25 km depth, at the boundary between the European and Adriatic tectonic plates, and in correspondence with the earlier identified Moho jump in the same area. The interpretation of a very shallow reaching IGB is further supported by the comparison of our new results with recent geophysical investigations, based on receiver functions and gravity anomaly data. By combining the new geophysical constraints and the geological observations at the surface, we provide a new structural interpretation of the IGB, which features lower crustal and mantle rocks at upper crustal depths. The comparison of the obtained v S values with the physical proper ties from laborator y analysis of local rock samples suggests that the bulk of the IGB consists of a combination of mantle peridotite, ultramafic and lower crustal rocks, bound in a heterogeneous structure. These new findings, based on v S tomography, corroborate the recent interpretation for which the Balmuccia peridotite outcrops are continuously linked to the IGB structure beneath. The new outcomes contribute to a multidisciplinary framework for the interpretation of the forthcoming results of the scientific drilling project DIVE. DIVE aims at probing the lower continental crust and its transition to the mantle, with two ongoing and one future boreholes (down to 4 km depth) in the IVZ area, providing new, complementar y infor mation on rock str ucture and composition across scales. In this framework, we constrain the upper crustal IGB geometries and lithology based on new evidence for v S , connecting prior crustal knowledge to recent active seismic investigations.
Trvalý link: https://hdl.handle.net/11104/0352045