Preprints
Filtering by Subject: Physical Sciences and Mathematics
Modeling deltaic lobe-building cycles and channel avulsions for the Yellow River delta, China
Published: 2019-09-10
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
River deltas grow by repeating cycles of lobe development punctuated by channel avulsions, so that over time, lobes amalgamate to produce a composite landform. Existing models have shown that backwater hydrodynamics are important in avulsion dynamics, but the effect of lobe progradation on avulsion frequency and location has yet to be explored. Herein, a quasi-2D numerical model incorporating [...]
The effect of remote sensing resolution limits on aeolian sandstone measurements and the reconstruction of ancient dune fields on Mars: Numerical experiment using the Page Sandstone, Earth
Published: 2019-09-10
Subjects: Physical Sciences and Mathematics, Planetary Geology, Planetary Sciences
The distribution of cross-set thicknesses is important field-collected data for reconstructing ancient aeolian dune fields from the strata they accumulated, but most aeolian strata on Mars must be observed with remote sensing. We hypothesize that remote sensing resolution limits will affect cross-set thickness measurements and the dune field reconstructions that follow. Here, we test this [...]
Bayesian elastic Full-Waveform Inversion using Hamiltonian Monte Carlo
Published: 2019-09-10
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a proof of concept for Bayesian elastic full-waveform inversion in 2-D. This is based on (1) Hamiltonian Monte Carlo sampling of the posterior distribution, (2) the computation of misfit derivatives using adjoint techniques, and (3) a mass matrix tuning of the Hamiltonian Monte Carlo algorithm that accounts for the different sensitivities of seismic velocities and density. We apply our [...]
An Adaptive Discontinuous Galerkin Method for the Simulation of Hurricane Storm Surge
Published: 2019-09-09
Subjects: Applied Mathematics, Other Applied Mathematics, Physical Sciences and Mathematics
Numerical simulations based on solving the 2D shallow water equations using a Discontinuous Galerkin (DG) discretisation have evolved to be a viable tool for many geophysical applications. In the context of flood modelling, however, they have not yet been methodologically studied to a large extent. On geographic scale, hurricane storm surge can be interpreted as a localised phenomenon making it [...]
Paradoxical impact of sprawling intra-Urban Heat Islets: Reducing mean surface temperatures while enhancing local extremes
Published: 2019-09-09
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Life Sciences, Physical Sciences and Mathematics, Statistics and Probability
Cities are at the forefront of climate change impacts and face a growing burden of adaptation to ensuing natural hazards. Extreme heat is a particularly challenging hazard as persistent heatwaves are locally exacerbated by the Urban Heat Island (UHI) effect. As a result, there is an increasing scientific interest in the influence of diverse urban morphologies on UHI. However, as the temperatures [...]
Recommended "Best Practices" for Chirp Acquisition and Processing
Published: 2019-09-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
This BOEM report describes details our experience/lessons learned in chirp subbottom data collection and processing.
Investigating global correlations between tsunami, earthquake, and subduction zone characteristics
Published: 2019-09-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Tsunamigenic earthquakes pose a large hazard in subduction zones, but it is currently unclear in which - if any - tectonic setting they preferentially occur. Here, we compile the global Subduction Nature & Interconnected Tsunamigenic earthquake Characteristics (SNITCH) database with parameters on subduction geometry and tectonics, megathrust seismicity, and tsunami characteristics of tsunamis [...]
Methods and Test Cases for Linking Physics-Based Earthquake and Tsunami Models
Published: 2019-09-06
Subjects: Computer Sciences, Earth Sciences, Geology, Geophysics and Seismology, Other Computer Sciences, Physical Sciences and Mathematics
Despite the inter-dependence of long term deformation, earthquakes and tsunamis, few modelling approaches bridge these processes. To advance the understanding of tsunami generation and earthquake-tsunami interactions, we present new methods for linking physics-based models of subduction zone geodynamics and seismic cycling, three-dimensional dynamic earthquake rupture, and tsunami generation, [...]
The 1987 to 2019 Tennant Creek, Australia, earthquake sequence: a protracted intraplate multi-mainshock sequence
Published: 2019-09-06
Subjects: Earth Sciences, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 1987 to 2019 Tennant Creek earthquake sequence comprises three 1988 surface-rupturing mainshocks (moment magnitude (Mw 6.2, 6.3, and 6.5) that occurred within a 12-hour period, a preceding foreshock sequence commencing in 1987, and a prolonged aftershock sequence including a Mw 5.0 earthquake on the 1st August 2019. Each surface rupturing event produced a distinct scarp; the south-dipping [...]
Grainstone cross-set geometry as a physical proxy for chemical and biological sediment cohesion
Published: 2019-09-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
Preserved cross-set thicknesses are powerful tools for unravelling past environmental conditions. The relative rate of bedform aggradation to migration (climb angle) is encoded into the distribution of cross-set thicknesses. In siliciclastic settings, climb angles have been used to reconstruct properties of the depositional system, including ancient topography, which exerts a control on local [...]
Coupled climate and subarctic Pacific nutrient upwelling over the last 850,000 years
Published: 2019-09-06
Subjects: Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
High latitude deep water upwelling has the potential to control global climate over glacial timescales through the biological pump and ocean-atmosphere CO2 exchange. However, there is currently a lack of continuous long nutrient upwelling records with which to assess this mechanism. Here we present geochemical proxy records for nutrient upwelling and glacial North Pacific Intermediate Water [...]
An equation of state for high pressure-temperature liquids (RTpress) with application to MgSiO3 melt
Published: 2019-09-06
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics
The thermophysical properties of molten silicates at extreme conditions are crucial for understanding the early evolution of Earth and other massive rocky planets, which is marked by giant impacts capable of producing deep magma oceans. Cooling and crystallization of molten mantles are sensitive to the densities and adiabatic profiles of high-pressure molten silicates, demanding accurate Equation [...]
Lower mantle structure from paleogeographically constrained dynamic Earth models
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Seismic tomography reveals two large, low-shear velocity provinces (LLSVPs) beneath Africa and the Pacific Ocean. These structures may have existed for several 100 Myr and are likely compositionally distinct based on observed seismic characteristics interpreted in light of geodynamic models and mineral physics constraints. We investigate the dynamics of the LLSVPs through the use of evolutionary [...]
Assimilating lithosphere and slab history in 4-D Earth models
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
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 [...]