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Preprints

Filtering by Subject: Physical Sciences and Mathematics

Assimilating lithosphere and slab history in 4-D Earth models

Dan James Bower, Michael Gurnis, Nicolas Flament

Published: 2019-09-06
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

We develop methods to incorporate paleogeographical constraints into numerical models of mantle convection. Through the solution of the convection equations, the models honor geophysical and geological data near the surface while predicting mantle flow and structure at depth and associated surface deformation. The methods consist of four constraints determined a priori from a plate history model: [...]

Dynamic origins of seismic wavespeed variation in D

Dan James Bower, Michael Gurnis, Daoyuan Sun

Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

The D discontinuity is defined by a seismic velocity increase of 1–3% about 250 km above the core–mantle boundary (CMB), and is mainly detected beneath locations of inferred paleosubduction. A phase change origin for the interface can explain a triplicated arrival observed in seismic waveform data and is supported by the recent discovery of a post-perovskite phase transition. We investigate the [...]

A geodynamic and mineral physics model of a solid-state ultralow-velocity zone

Dan James Bower, June K. Wicks, Michael Gurnis, et al.

Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Recent results (Wicks et al., 2010) suggest that a mixture of iron-enriched (Mg,Fe)O and ambient mantle is consistent with wavespeed reductions and density increases inferred for ultralow-velocity zones (ULVZs). We explore this hypothesis by simulating convection to deduce the stability and morphology of such chemically-distinct structures. The buoyancy number, or chemical density anomaly, [...]

Melt inclusion constraints on mantle carbon heterogeneity within an individual mantle plume and at the global scale

Simon Matthews, Oliver Shorttle, John Maclennan, et al.

Published: 2019-09-06
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics

The Earth’s mantle holds more carbon than its oceans, atmosphere and continents combined, yet the distribution of carbon within the mantle remains uncertain. Global variations in the carbon content of the depleted mantle have been inferred from carbon-trace element systematics of ultra-depleted mid-ocean ridge glasses and melt inclusions, though the origin of mantle carbon variability remains [...]

Enhanced Convection and Fast Plumes in the Lower Mantle Induced by the Spin Transition in Ferropericlase

Dan James Bower, Michael Gurnis, Jennifer M. Jackson, et al.

Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Using a numerical model we explore the consequences of the intrinsic density change (Δρ/ρ ≈ 2–4%) caused by the Fe2+ spin transition in ferropericlase on the style and vigor of mantle convection. The effective Clapeyron slope of the transition from high to low spin is strongly positive in pressure‐temperature space and broadens with high temperature. This introduces a net spin‐state driving [...]

Re-evaluating 14C dating accuracy in deep-sea sediment archives.

Bryan C. Lougheed, Philippa Ascough, Andrew Dolman, et al.

Published: 2019-09-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics

The current geochronological state of the art for applying the radiocarbon (14C) method to deep-sea sediment archives lacks key information on sediment bioturbation. Here, we apply a sediment accumulation model that simulates the sedimentation and bioturbation of millions of foraminifera, whereby realistic 14C activities (i.e. from a 14C calibration curve) are assigned to each single foraminifera [...]

Hydropower dependency and climate change in sub-Saharan Africa: A nexus framework and evidence-based review

Giacomo Falchetta, David Gernaat, Julian Hunt, et al.

Published: 2019-09-06
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Environmental Studies, International and Area Studies, Physical Sciences and Mathematics, Social and Behavioral Sciences

In sub-Saharan Africa, 160 million grid-connected electricity consumers live in countries where hydropower accounts for over 50% of total power supply. A warmer climate with more frequent and intense extremes could result in supply reliability issues. Here, (i) a robust framework to highlight the interdependencies between hydropower, water availability, and climate change is proposed, (ii) the [...]

On seismicity and structural style of oceanic transform faults: a field geological perspective from the Troodos ophiolite, Cyprus

Ake Fagereng, Chris MacLeod

Published: 2019-09-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure

Aseismic creep accommodates the majority of displacement along active oceanic transform faults, also within their thermally defined seismogenic zone. The significant earthquakes that do occur are near periodic, and repeat in nearly constant locations. Neither of these observations is explained by current models that infer an olivine-dominated rheology and a thermally controlled seismogenic zone. [...]

Building back bigger in hurricane strike zones

Eli Lazarus, Patrick W Limber, Evan B Goldstein, et al.

Published: 2019-09-03
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Geomorphology, Physical Sciences and Mathematics, Sustainability

Despite decades of regulatory efforts in the United States to decrease vulnerability in developed coastal zones, exposure of residential assets to hurricane damage is increasing — even in places where hurricanes have struck before. Comparing plan-view footprints of individual residential buildings before and long after major hurricane strikes, we find a systematic pattern of ‘building back [...]

The near-tip region of a hydraulic fracture with pressure-dependent leak-off and leak-in

Evgenii Kanin, Dmitry Garagash, Andrei Osiptsov

Published: 2019-09-03
Subjects: Earth Sciences, Engineering, Environmental Sciences, Hydrology, Oil, Gas, and Energy, Physical Sciences and Mathematics, Volcanology

This paper is concerned with an analysis of the near tip region of a propagating fluid-driven fracture in a saturated permeable rock. The study attempts to accurately resolve the coupling between the physical processes - rock breakage, fluid pressure drop in the viscous fluid flow in the fracture, and fluid exchange between fracture and the rock - that exert influence on the hydraulic fracture [...]

Frictional heterogeneities can promote disordered slip evolution on faults

Sohom Ray

Published: 2019-09-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

We consider that a slip instability nucleates an earthquake. Past studies found blow-up solutions for diverging slip velocities. Prior stability analyses, considering heterogeneous frictional properties revealed that stable blow-up solutions can predictably dictate earthquake-nucleating instabilities. In this prior analysis, the focus remained mainly on the attraction to stable blow-up [...]

Emergent self-similarity and scaling properties of fractal intra-Urban Heat Islets for diverse global cities

Anamika Shreevastava, P. Suresh C. Rao, Gavan McGrath

Published: 2019-09-02
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Physical Sciences and Mathematics, Statistics and Probability

Urban areas experience elevated temperatures due to the Urban Heat Island (UHI) effect. However, temperatures within cities vary considerably and their spatial heterogeneity is not well characterized. Here, we use Land Surface Temperature (LST) of 78 global cities to show that the Surface UHI (SUHI) is fractal. We use percentile-based thermal thresholds to identify heat clusters emerging within [...]

Comparing Aggradation, Superelevation, and Avulsion Frequency of Submarine and Fluvial Channels

Zane Richards Jobe, Nick Howes, Kyle M. Straub, et al.

Published: 2019-08-30
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy

IN REVIEW IN "FRONTIERS IN EARTH SCIENCE" (30 Aug 2019). Constraining the avulsion dynamics of rivers and submarine channels is essential for predicting the distribution and architecture of sediment, organic matter and pollutants in alluvial, deltaic, and submarine settings. Submarine channels are well known to be more aggradational than rivers, and aggradation of the channel, levee, and [...]

Controls on variations in minibasin geometries: Lower Congo Basin, offshore Angola

Zhiyuan Ge, Robert Leslie Gawthorpe, Leo Zijerveld, et al.

Published: 2019-08-30
Subjects: Earth Sciences, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure

In passive margin salt basins, the distinct tectonic domains of thin-skinned extension and contraction exert important controls on the geometry and evolution of minibasins. In this study, we use a semi-regional 3D seismic dataset from the Lower Congo Basin to investigate the spatial and temporal evolution of a network of salt-related minibasins and intervening salt walls and diapirs during [...]

Subduction history reveals Cretaceous slab superflux as a possible cause for the mid-Cretaceous plume pulse and superswell events

Madison East, R. Dietmar Müller, Simon Williams, et al.

Published: 2019-08-29
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure

Subduction is a fundamental mechanism of material exchange between the planetary interior and the surface. Despite its significance, our current understanding of fluctuating subducting plate area and slab volume flux has been limited to a range of proxy estimates. Here we present a new detailed quantification of subduction zone parameters from the Late Triassic to present day (230 – 0 Ma). We use [...]

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