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On the Relationship Between Oceanic Plate Speed, Tectonic Stress, and Seismic Anisotropy.

ABSTRACT: Seismic radial anisotropy (the squared ratio between the speeds of horizontally and vertically polarized shear waves, ξ=VSH2VSV2 ) is a powerful tool to probe the direction of mantle flow and accumulated strain. While previous studies have confirmed the dependence of azimuthal anisotropy on plate speed, the first order control on radial anisotropy is unclear. In this study, we develop 2D ridge flow models combined with mantle fabric calculations to report that faster plates generate higher tectonics stresses and strain rates which lower the dislocation creep viscosity and lead to deeper anisotropy than beneath slower plates. We apply the SGLOBE-rani tomographic filter, resulting in a flat depth-age trend and stronger anisotropy beneath faster plates, which correlates well with 3D global anisotropic mantle models. Our predictions and observations suggest that as plate speed increases from 2 to 8 cm/yr, radial anisotropy increases by ∼0.01-0.025 in the upper 100-200 km of the mantle between 10 and 60 Ma.

SUBMITTER: Kendall E

PROVIDER: S-EPMC9539886 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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On the Relationship Between Oceanic Plate Speed, Tectonic Stress, and Seismic Anisotropy.

Kendall E E Faccenda M M Ferreira A M G AMG Chang S-J SJ

Geophysical research letters 20220810 15

Seismic radial anisotropy (the squared ratio between the speeds of horizontally and vertically polarized shear waves, ξ = V S H 2 V S V 2 ) is a powerful tool to probe the direction of mantle flow and accumulated strain. While previous studies have confirmed the dependence of azimuthal anisotropy on plate speed, the first order control on radial anisotropy is unclear. In this study, we develop 2D ridge flow models combined with mantle fabric calculations to report that faster plates gene ...[more]

PMID: 36247518

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Project description:Our knowledge of subsurface structures often derives from seismic velocities that are measured during seismic acquisition surveys. These velocities can greatly change due to lithological, fracture frequencies and/or effective pressure/temperature variations. However, the influence of such intrinsic lithological properties and environmental conditions at the large scale is poorly understood due to the lack of comprehensive datasets. Here, we analyze 43 borehole-derived velocity datasets of 3 end-member tight carbonate sequences from Central Italy, including massive pure limestone (Calcare Massiccio, CM), thick-layered (20-50 cm) pure limestone (Maiolica, MA), and thin-layered (2-20 cm) marly limestone (Calcareous Scaglia, CS). Our results show that the main rock parameters and environmental conditions driving large scale velocity variations are bedding and paleostresses, while mineralogical composition and current tectonic stress also play a role. For each of the 3 end-members, measured VP values vary differently with depth, as the thin-layered CS units show a clear increase in Vp, while velocity slightly increases and remains constant for the thick-layered MA and massive CM units, respectively. Such observations show that velocities are affected by specific characteristics of lithological discontinuities, such as the thickness of bedding. Counterintuitively, larger Vp values were recorded in the deformed mountain range than in the undeformed foreland suggesting that higher paleo-stresses increase velocity values by enhancing diagenesis and healing of discontinuities. Our results thus demonstrate that large scale velocity variations are strictly related to variation of lithological properties and to the geological and tectonic history of an area. We suggest that such lithological and environmental controls should be taken into account when developing velocity and mechanical models for tectonically active regions of the Mediterranean Area, where earthquakes mostly nucleate and propagate through carbonate formations, and for resource exploration in fractured carbonate reservoirs.

Dataset Information

On the Relationship Between Oceanic Plate Speed, Tectonic Stress, and Seismic Anisotropy.

Publications

On the Relationship Between Oceanic Plate Speed, Tectonic Stress, and Seismic Anisotropy.

Similar Datasets

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