Inference of thermodynamic state in the asthenosphere from anelastic properties, with applications to North American upper mantle

Havlin, C.; Holtzman, B. K.; Hopper, Emily

doi:10.31223/x5c59z

Cited by 6 publications

(13 citation statements)

References 121 publications

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“…To calculate the temperature structure, we assume a thermal diffusivity of 1 × 10 −6 m 2 s −1 , and a mantle potential temperature of 1350°C calculated for seafloor age from 0 to 40 Myr, the approximate range in of ages along lines I and II (Figure 4). To model the predicted shear velocity for a given temperature, pressure, and melt fraction we use the Very Broadband Rheology calculator (Havlin et al., 2021), assuming a peridotite mantle composition. We use the attenuation parameterization of (Jackson & Faul, 2010) that is included in the calculator and use an average across the surface wave period range used here, 18–143 s period.…”

Section: Methodsmentioning

confidence: 99%

Shear Velocity Inversion Guided by Resistivity Structure From the PI‐LAB Experiment for Integrated Estimates of Partial Melt in the Mantle

et al. 2021

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Plate tectonic theory is predicated on the idea of a rigid lithosphere that overrides a weaker underlying asthenosphere (McKenzie & Parker, 1967), but the nature of the lithosphere-asthenosphere system remains the subject of vigorous debate. The oceanic lithosphere comprises the majority of the surface of the Earth and has the simplest evolution and history. It is classically thought to be thermally defined as a boundary layer in a simple thermal model (Parker & Oldenburg, 1973). In this model, increasing temperature with depth causes mantle rocks to weaken, creating the asthenosphere (e.g.,

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Section: Methodsmentioning

confidence: 99%

Shear Velocity Inversion Guided by Resistivity Structure From the PI‐LAB Experiment for Integrated Estimates of Partial Melt in the Mantle

et al. 2021

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“…While this approach is rational for steady state diffusion creep, many open questions remain on the scaling for transient diffusion creep and interactions with dislocation processes, discussed in, for example, Cooper (2002), Faul and Jackson (2015), Takei (2017), and Havlin et al. (2021).…”

Section: The Full Spectrum Of Viscoelastic Deformationmentioning

confidence: 99%

“…To do this we will rely on a recently released open‐source software library, the “Very Broadband Rheology calculator” (VBRc), developed by several of the co‐authors here (Havlin et al., 2021). This software takes as input the thermodynamic conditions and other state variables,

S

—where

S = false[T, P, ϕ, g, σ, X false]

(temperature, pressure, melt fraction, grain size, stress state, and composition, respectively)—and determines the full spectrum mechanical properties for a selection of constitutive laws.…”

Section: The Full Spectrum Of Viscoelastic Deformationmentioning

confidence: 99%

“…The VBRc then outputs the complex modulus,

M^{*} (ω)

, the dissipation,

Q^{‐ 1} (ω)

, from which the complex viscosity

η^{*} (ω)

(Lau & Holtzman, 2019) can be computed (Section 2.2). In the initial release of the VBRc, the composition is limited to olivine and the laboratory‐derived rheological laws remain the focus (Havlin et al., 2021).…”

Section: The Full Spectrum Of Viscoelastic Deformationmentioning

confidence: 99%

“…In between these endmembers is the anelastic or transient regime, which is currently being explored by several laboratories working on olivine samples (e.g., Faul & Jackson, 2015; Jackson & Faul, 2010; Sundberg & Cooper, 2010) and analog materials (Takei, 2017). This work is building toward a clearer picture of the grain‐scale processes that govern macroscopic transient creep, including both diffusion‐ and dislocation‐ (both linear and non‐linear) related grain boundary and intracrystalline deformation mechanisms (e.g., Hansen et al., 2019; Karato & Wu, 1993) (see Havlin et al., 2021 for a summary of these processes). From these microphysical mechanisms, distinct frequency‐dependent rheological properties of rock can be predicted.…”

Section: Introductionmentioning

confidence: 99%

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Frequency Dependent Mantle Viscoelasticity via the Complex Viscosity: Cases From Antarctica

et al. 2021

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The growth and decay of ice sheets over the Pleistocene represent large variations in Earth's climate system and induce significant deformation of the solid Earth. This deformation (including associated changes to Earth's stress and gravity field, and its rotation axis), in response to the redistribution of ice and ocean mass, is known as "glacial isostatic adjustment" (GIA). Areas that were formerly covered by or close to major ice sheets during the last glacial period, such as Fennoscandia, Greenland, North America and Antarctica, continue to experience the highest rates of GIA-related deformation today, even though ice has retreated partially or entirely (e.g., Sella et al., 2007). Pertinent to understanding this solid Earth deformation, and, as a consequence, related climatological feedbacks (e.g., Larour et al., 2019;Pan et al., 2021) is knowledge of the planet's viscoelastic structure. Constraining Earth's viscoelastic structure has been the focus of many GIA, geodynamic, seismic, and mineral/rock physics studies. In GIA studies, viscoelastic deformation is often assumed to be linear with one

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Toward a Self‐Consistent Characterization of Lithospheric Plates Using Full‐Spectrum Viscoelasticity

2020

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Determining the thickness of the lithosphere in any given setting combines uncertainty in both the observational method and laboratory-derived understanding of mantle rheology. The many observational and modeling criteria across geophysical subfields for plate thickness lead to significant differences in plate thickness estimates depending on the process of interest, be it seismic wave propagation or relaxation in response to changes in loads-from earthquakes, ice sheets to volcanoes-or convection. This paper proposes a framework in which to model and interpret upper mantle mechanical structure smoothly across the full spectrum of geophysical timescales. We integrate viscous, elastic, and linear anelastic constitutive models and calculate the mechanical response from convective to seismic wave timescales (i.e., 0 to infinite frequency or, in practice, 10 −15 to 1 Hz). We apply these calculations to 1-D thermal structures and determine the normalized complex viscosity, a quantity that shows clearly the role of transient creep in weakening rock relative to the associated Maxwell rheology. Using various criteria for the lithosphere-asthenosphere boundary, we show that the apparent plate thickness will be thicker at higher frequencies than at lower frequencies. Additional calculations for nonlinear Maxwell behavior (dislocation mechanisms) demonstrate significant changes in the apparent plate structure, decreasing the long-term plate thickness, consistent with observations. Other effects such as dislocation damping (associated with a steady-state dislocation structure), melt, water, major element composition, and grain size are not included here but, when incorporated into this framework, will significantly change the full-spectrum plate thickness predictions. Plain Language Summary On Earth, broken, rigid tectonic plates lie atop slowly flowing mantle rock (over millions to billions of years). A basic understanding of the global variation in thickness of this rigid lid provides the foundation to many geodynamical predictions. However, using different techniques to estimate its thickness, for example, seismic wave propagation (acting on timescales of seconds), to the warping of plates under the weight of volcanoes (acting on timescales of millions of years) reveals many inconsistencies. At the heart of these inconsistencies is the fact that rock deforms differently to forces acting on different timescales. At very fast timescales rock deforms like an elastic solid, but at much longer timescales, rock flows. To resolve these inconsistencies, we attempt to coherently tie these disparate observations together to reach a more holistic understanding of plate thickness, accounting for these timescale effects. By incorporating current understanding on rock deformation from laboratory experiments, we demonstrate that on fast timescales (of the seismic waves used to image the Earth's interior), tectonic plates appear significantly thicker than the true thickness at million-to billion-year timescales of plate tectonics. This d...

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Inference of thermodynamic state in the asthenosphere from anelastic properties, with applications to North American upper mantle

Cited by 6 publications

References 121 publications

Shear Velocity Inversion Guided by Resistivity Structure From the PI‐LAB Experiment for Integrated Estimates of Partial Melt in the Mantle

Shear Velocity Inversion Guided by Resistivity Structure From the PI‐LAB Experiment for Integrated Estimates of Partial Melt in the Mantle

Frequency Dependent Mantle Viscoelasticity via the Complex Viscosity: Cases From Antarctica

Toward a Self‐Consistent Characterization of Lithospheric Plates Using Full‐Spectrum Viscoelasticity

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