Preprints
There are 4725 Preprints listed.
Denoising ambient seismic field correlation functions with convolutional autoencoders
Published: 2019-07-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Seismic interferomestry is an established method for monitoring the temporal evolution of the Earths physical properties. We introduce a new technique to improve the precision and temporal resolution of seismic monitoring studies based on deep learning. Our method uses a convolutional denoising autoencoder, called ConvDeNoise, to denoise ambient seismic field correlation functions. The technique [...]
The impact of Mg2+ ions on equilibration of Mg-Ca carbonates in groundwater and brines
Published: 2019-07-04
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
At temperatures below 50°C, the Mg2+/Ca2+ values in groundwater and brines, irrespective of their origin - either carbonaceous or siliceous rocks/sediments - show a large spread. As shown by equilibria of surface layer composition of calcite in solutions containing Mg2+ , log10 (aMg2+ /a Ca2+) vary between minus infinity and +2.3, thereby covering thermodynamical equilibria between the minerals [...]
A bedform phase diagram for dense granular currents
Published: 2019-07-04
Subjects: Earth Sciences, Fluid Dynamics, Geology, Physical Sciences and Mathematics, Physics, Sedimentology, Volcanology
Pyroclastic density currents are a life-threatening volcanic hazard. Our understanding and hazard assessments of these flows primarily rely on interpretations of their deposits. The occurrence of stratified layers, cross-stratification, and dune bedforms in these deposits has been assumed as indicative of dilute, turbulent, flows causing traction-dominated deposition. Here we show, through [...]
Segmentation of the Main Himalayan Thrust inferred from geodetic observations of interseismic coupling
Published: 2019-07-04
Subjects: Computer Sciences, Earth Sciences, Environmental Sciences, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics, Probability, Statistics and Probability, Tectonics and Structure
Mapping the distribution of locked segments along subduction megathrusts is essential for improving quantitative assessments of seismic hazard. Previous geodetic studies suggest the Main Himalayan Thrust (MHT) is homogeneously locked (or coupled) along its complete length over a down-dip extent of ~100 km. However, an increasing number of seismological and geophysical observations suggests the [...]
The Glacial Origins of Relict Pingos, Wales, UK
Published: 2019-07-04
Subjects: Earth Sciences, Geomorphology, Glaciology, Physical Sciences and Mathematics
Ramparted depressions (doughnut-shaped debris-cored ridges with peat- and/or sediment-filled central basins) are commonly perceived to represent the relict collapsed forms of permafrost ground-ice mounds (i.e. pingos or lithalsas). In Wales, UK, ramparted depressions of Late Pleistocene age have been widely attributed to permafrost-related processes. However, a variety of alternative glacial [...]
Evidence against a general positive eddy feedback in atmospheric blocking
Published: 2019-07-04
Subjects: Atmospheric Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
The eddy straining mechanism of Shutts (1983; S83) has long been considered a main process for explaining the maintenance of atmospheric blocking. As hypothesized in S83, incoming synoptic eddies experience a meridional straining effect when approaching a split jetstream, and as a result, enhanced PV fluxes reinforce the block. A two-layer QG model is adopted here as a minimal model to conduct [...]
From prodigious volcanic degassing to caldera subsidence and quiescence at Ambrym (Vanuatu): the influence of regional tectonics
Published: 2019-06-28
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Eruptive activity shapes volcanic edifices. The formation of broad caldera depressions is often associated with major collapse events, emplacing conspicuous pyroclastic deposits. However, caldera subsidence may also proceed silently by magma withdrawal at depth, more difficult to detect. Ambrym, a basaltic volcanic island, hosts a 12-km wide caldera and several intensely-degassing lava lakes [...]
Certified Reduced Basis Method in Geosciences Addressing the challenge of high dimensional problems
Published: 2019-06-28
Subjects: Applied Mathematics, Earth Sciences, Numerical Analysis and Computation, Partial Differential Equations, Physical Sciences and Mathematics
One of the biggest challenges in Computational Geosciences is finding ways of efficiently simulating high-dimensional problems. In this paper, we demonstrate how the RB method can be gainfully exploited to solve problems in the Geosciences. The reduced basis method constructs low-dimensional approximations to (high-dimensional) solutions of parametrized partial differential equations. In contrast [...]
What sets the width of a river?
Published: 2019-06-28
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Alluvial rivers are formed by, and are an expression of, the water and sediment that they convey. They are the primary arteries of water and nutrients on land, making them the lifeblood of communities and commerce. While a myriad of environmental and geological factors have been proposed to control alluvial river size, near-universal scaling relations between channel geometry and discharge [...]
Increasing dependence of lowland population on mountain water resources
Published: 2019-06-28
Subjects: Earth Sciences, Hydrology, Physical Sciences and Mathematics
Mountain areas provide disproportionally high runoff in many parts of the world, but their importance for lowland water resources and food production has not been clarified so far. Here we quantify for the first time the extent to which lowland inhabitants potentially depend on runoff contributions from mountain areas (39% of land mass). We show that ~1.4 billion people (23% of world’s lowland [...]
Lateral variability of shelf-edge, slope and basin-floor deposits, Santos Basin, offshore Brazil
Published: 2019-06-28
Subjects: Earth Sciences, Engineering, Geology, Physical Sciences and Mathematics, Sedimentology
Construction of continental margins is driven by sediment transported across the shelf to the shelf-edge, where it is reworked by wave-, tide- and river-influenced processes within deltas and flanking clastic shorelines. Stalling of continental margin progradation often results in degradation of the outer shelf to upper slope, with re-sedimentation to the lower slope and basin-floor via a range [...]
Reducing uncertainties in climate projections with emergent constraints: Concepts, Examples and Prospects
Published: 2019-06-28
Subjects: Atmospheric Sciences, Climate, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Models disagree on a significant number of responses to climate change, such as climate feedback, regional changes, or the strength of equilibrium climate sensitivity. Emergent constraints aim to reduce these uncertainties by finding links between the inter-model spread in an observable predictor and climate projections. In this paper, the concepts underlying this framework are recalled with an [...]
Is it always Slowdown of the Walker circulation at solar cycle maximum?
Published: 2019-06-27
Subjects: Atmospheric Sciences, Climate, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
It is a commentary following a published paper in PNAS titled, ‘Slowdown of the Walker circulation at solar cycle maximum’, by Stergios Misios, Lesley J. Gray, Mads F. Knudsen, Christoffer Karoff, Hauke Schmidt, and Joanna D. Haigh (2019). The article of Misios et.al.(2019) claims that there is a slowdown of the Walker Circulation during maximum periods of solar cycles. In support, they provided [...]
More hots: Quantifying upward trends in the number of extremely hot days and nights in Tallahassee, Florida, USA: 1892–2018
Published: 2019-06-27
Subjects: Earth Sciences, Physical Sciences and Mathematics
The U.S. National Weather Service Office (WSO) Tallahassee official record shows an upward trend in the number of hot days at a rate of 2.1% per year and a more pronounced upward trend in the number of hot nights at a rate of 4.5% per year. Increasingly frequent hot days and nights result from more and longer hot events (consecutive hot days/nights).
Dynamical Systems Theory Sheds New Light on Compound Climate Extremes in Europe and Eastern North America
Published: 2019-06-27
Subjects: Applied Mathematics, Atmospheric Sciences, Climate, Dynamic Systems, Earth Sciences, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics, Statistical, Nonlinear, and Soft Matter Physics
We propose a novel approach to the study of compound extremes, grounded in dynamical systems theory. Specifically, we present the co-recurrence ratio (α), which elucidates the dependence structure between variables by quantifying their joint recurrences. This approach is applied to daily climate extremes, derived from the ERA-Interim reanalysis over the 1979-2018 period. The analysis focuses on [...]