Preprints
Filtering by Subject: Earth Sciences
A geodynamic and mineral physics model of a solid-state ultralow-velocity zone
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
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
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.
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
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
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
Published: 2019-09-04
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
Published: 2019-09-04
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
Published: 2019-09-04
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
Published: 2019-09-03
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
Published: 2019-08-31
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
Published: 2019-08-31
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
Published: 2019-08-30
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 [...]
Anatomy of exhumed river-channel belts: Bedform- to belt-scale kinematics of the Ruby Ranch Member, Cretaceous Cedar Mountain Formation, Utah, USA
Published: 2019-08-30
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
Many published interpretations of ancient fluvial systems have relied on observations of extensive outcrops of thick successions. This paper, in contrast, demonstrates that a regional understanding of paleoriver kinematics, depositional setting, and sedimentation rates can be interpreted from local sedimentological measurements of bedform and barform strata. Dune and bar strata, channel planform [...]
Accounting for training data error in machine learning applied to Earth observations
Published: 2019-08-30
Subjects: Earth Sciences, Engineering, Environmental Monitoring, Environmental Sciences, Life Sciences, Physical Sciences and Mathematics
Remote sensing, or Earth Observation (EO), is increasingly used to understand Earth system dynamics and create continuous and categorical maps of biophysical properties and land cover, especially based on recent advances in machine learning (ML). ML models typically require large, spatially explicit training datasets to make accurate predictions. Training data (TD) are typically generated by [...]