Lithospheric structure of the eastern Mediterranean Sea: Inferences from surface wave tomography and stochastic inversions constrained by wide-angle refraction measurements

El‐Sharkawy, Amr; Meier, Thomas; Hübscher, Christian; Lebedev, Sergei; Dannowski, Anke; Kopp, Heidrun; Behrmann, Jan H.; McGrandle, A.; Hamada, M.

doi:10.1016/j.tecto.2021.229159

Cited by 8 publications

(5 citation statements)

References 148 publications

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“…This is especially true in correspondence of oceanic basins and/or mid‐oceanic ridges, where the serpentinization of mantle rocks can represent a complicating factor by reducing the otherwise strong velocity contrast between the sedimentary cover and the metamorphosed mantle terrains. A joint analysis of surface‐wave dispersion curves and deep‐seismic‐sounding (DSS) data may mitigate this problem, by yielding an additional constraint on the V P / V S ratios at those locations where DSS data are available (El‐Sharkawy et al., 2021).…”

Section: Resultsmentioning

confidence: 99%

Surface‐Wave Tomography of the Central‐Western Mediterranean: New Insights Into the Liguro‐Provençal and Tyrrhenian Basins

et al. 2022

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The complex tectonic setting of the central‐western Mediterranean has interested geoscientists for decades, but its geodynamic evolution remains a matter of debate. We rely on 807 seismometers from southern Europe and northern Africa to measure Rayleigh and Love phase velocities in the period range ∼5–200 s, based on teleseismic earthquakes and seismic ambient noise. By nonlinear joint inversion of the phase‐velocity maps, we obtain a 3‐D shear‐wave velocity (VS) model of the study area. At shallow depths, our model correlates with surface geology and reveals the presence of a sedimentary cover in the Liguro‐Provençal basin, as opposed to the Tyrrhenian basin where this is either very thin or absent. At ∼5‐km depth, high velocities below the Magnaghi, Vavilov, and Marsili seamounts point to an exhumed, scarcely serpentinized mantle. These are replaced by lower velocities at larger depths, likely connected to the presence of partial melt. At 50–60‐km depth, a very heterogeneous structure characterizes the Tyrrhenian basin, with low velocities pointing to the presence of fluids due to the lateral mantle inflow from the Ionian slab edges, and higher velocities associated with a relatively dry upper mantle. Such heterogeneity disappears at depths ≳75 km, replaced by more uniform velocities which are ∼2% lower than those found in the Liguro‐Provençal basin. We infer that, at the same depths, the Tyrrhenian basin is characterized by a larger concentration of fluids and possibly higher temperatures.

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Section: Resultsmentioning

confidence: 99%

Surface‐Wave Tomography of the Central‐Western Mediterranean: New Insights Into the Liguro‐Provençal and Tyrrhenian Basins

et al. 2022

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“…We consider the recent surface‐wave tomographic study of El‐Sharkawy et al. (2020) (Figure 16), which shows strong low shear‐velocity anomalies beneath the SCRZ, from 75 to 300 km depth (El‐Sharkawy et al., 2021). Thus, the low velocity we observe beneath the SCRZ is unlikely a result of passive vertical flow due to the rifting process above because, if so, the low V S would only be present a few tens of kilometers beneath the thinned lithosphere (e.g., West et al., 2004).…”

Section: Discussionmentioning

confidence: 99%

“…These zones of low shear velocities are a proxy for high temperatures that facilitate vertical flow, as inferred from the strong negative radial anisotropy (Figure 16). A deeper low shear velocity beneath the SCRZ (El‐Sharkawy et al., 2020, 2021) suggests that upwelling has a mantle origin, possibly from poloidal flow that contributes to the negative radial anisotropy, volcanism, and an elevated residual topography.…”

Section: Discussionmentioning

confidence: 99%

“…Instead, it is thought that the nearby subducted lithosphere has a slab window (or gap) which could affect the mantle circulation (e.g., Booth-Rea et al, 2018;Faccenna et al, 2007;Faccenna et al, 2011). We consider the recent surface-wave tomographic study of El-Sharkawy et al (2020) (Figure 16), which shows strong low shear-velocity anomalies beneath the SCRZ, from 75 to 300 km depth (El-Sharkawy et al, 2021). Thus, the low velocity we observe beneath the SCRZ is Comparison of radial anisotropy with intraplate (red) and subduction-related volcanism (blue) (Faccenna et al, 2005).…”

Section: Upper Mantle Dynamics: Thin Lithosphere and Vertical Mantle ...mentioning

confidence: 99%

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Shear‐Velocity Structure and Dynamics Beneath the Sicily Channel and Surrounding Regions of the Central Mediterranean Inferred From Seismic Surface Waves

Agius

Magrini

Diaferia

et al. 2022

Geochem Geophys Geosyst

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The central Mediterranean is made up of complex tectonic processes dominated by the northward slow convergence of the African continent with the Eurasian plate (Dewey et al., 1989) and the Calabrian subduction system retreating south-eastwards (Malinverno & Ryan, 1986). This area has been evolving for at least the last 30 My as the Calabrian subducting lithosphere rolled back from the west to the central Mediterranean (e.g., Carminati,

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“…While global compilations of Wadati-Benioff zone seismicity plot broad, trench-parallel swaths of events to show a first-order trend of widening separation between the upper and lower planes of Wadati-Benioff zones with increasing age (or the thermal parameter derived from age) in the ~10-160-m.y.-old subducting oceanic lithosphere of the Indo-Pacific basins (Brudzinski et al, 2007;Florez and Prieto, 2019), other observations suggest that additional factors strongly affect this relationship. Most significantly, the 220-340-m.y.-old oceanic lithosphere (Speranza et al, 2012;Granot, 2016;Dannowski et al, 2019;El-Sharkawy et al, 2021;Segev et al, 2018, and references therein) subducting beneath the Hellenic arc shows only a single Wadati-Benioff zone plane (Halpaap et al, 2019). Likewise, the 90-110-m.y.-old lithosphere (Müller et al, 2008) subducting beneath the Lesser Antilles arc exhibits a single Wadati-Benioff zone plane (Bie et al, 2019).…”

Section: ■ Introductionmentioning

confidence: 99%

Oceanic intraplate faulting as a pathway for deep hydration of the lithosphere: Perspectives from the Caribbean

et al. 2022

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The recycling of water into the Earth’s mantle via hydrated oceanic lithosphere is believed to have an important role in subduction zone seismicity at intermediate depths. Hydration of oceanic lithosphere has been shown to drive double planes of intermediate-depth, Wadati-Benioff zone seismicity at subduction zones. However, observations from trenches show that pervasive normal faulting causes hydration ~25 km into the lithosphere and can explain neither locations where separations of 25–40 km between Wadati-Benioff zone planes are observed nor the spatial variability of the lower plane in these locations, which suggests that an additional mechanism of hydration exists. We suggest that intraplate deformation of >50-m.y.-old lithosphere, an uncommon and localized process, drives deeper hydration. To test this, we relocated the 25 November 2018 6.0 MW Providencia, Colombia, earthquake mainshock and 575 associated fore- and aftershocks within the interior of the Caribbean oceanic plate and compared these with receiver functions (RF) that sampled the fault at its intersection with the Mohorovičić discontinuity. We examined possible effects of velocity model, initial locations of the earthquakes, and seismic-phase arrival uncertainty to identify robust features for comparison with the RF results. We found that the lithosphere ruptured from its surface to a depth of ~40 km along a vertical fault and an intersecting, reactivated normal fault. We also found RF evidence for hydration of the mantle affected by this fault. Deeply penetrating deformation of lithosphere like that we observe in the Providencia region provides fluid pathways necessary to hydrate oceanic lithosphere to depths consistent with the lower plane of Wadati-Benioff zones.

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Lithospheric structure of the eastern Mediterranean Sea: Inferences from surface wave tomography and stochastic inversions constrained by wide-angle refraction measurements

Cited by 8 publications

References 148 publications

Surface‐Wave Tomography of the Central‐Western Mediterranean: New Insights Into the Liguro‐Provençal and Tyrrhenian Basins

Surface‐Wave Tomography of the Central‐Western Mediterranean: New Insights Into the Liguro‐Provençal and Tyrrhenian Basins

Shear‐Velocity Structure and Dynamics Beneath the Sicily Channel and Surrounding Regions of the Central Mediterranean Inferred From Seismic Surface Waves

Oceanic intraplate faulting as a pathway for deep hydration of the lithosphere: Perspectives from the Caribbean

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