Preprints
There are 6976 Preprints listed.
The morphology, evolution and seismic visibility of partial melt at the core-mantle boundary: Implications for ULVZs
Published: 2021-04-14
Subjects: Geophysics and Seismology
Seismic observations indicate that the lowermost mantle above the core-mantle boundary is strongly heterogeneous. Body waves reveal a variety of ultra-low velocity zones (ULVZs), which extend not more than 100 km above the core-mantle boundary and have shear velocity reductions of up to 30%. While the nature and origin of these ULVZs remain uncertain, some have suggested they are evidence of [...]
Microstructural differences between naturally-deposited and laboratory beach sands
Published: 2021-04-14
Subjects: Civil and Environmental Engineering, Civil Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics, Sedimentology
The orientation of and contacts between grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. We compare naturally-deposited beach sands [...]
The state of pore fluid pressure and 3D megathrust earthquake dynamics
Published: 2021-04-14
Subjects: Earth Sciences
The importance of pore fluid pressure (Pf) for fault strength, stress state and slip behavior holds promise for explaining spatio-temporal subduction zone megathrust behavior, but the coseismic state of Pf and its distribution with depth are poorly constrained. Here, we analyze fault stress states and 3D rupture dynamics of six scenarios based on the 2004 Mw 9.1 Sumatra-Andaman earthquake. We [...]
Controls on the distribution of hydrous defects in forsterite from a thermodynamic model
Published: 2021-04-15
Subjects: Physical Sciences and Mathematics
The distribution of hydrogen across different crystallographic sites and point defects in forsterite is important because it determines how many properties, such as rheology, conductivity, diffusion and elemental partitioning are affected by water. In this study we use lattice dynamics and Density Functional Theory (DFT) to build a thermodynamic model of H-bearing defects that incorporates both [...]
Particulate PhozzyLogic Index for policy makers—an index for a more accurate and transparent identification of critical source areas
Published: 2021-04-20
Subjects: Environmental Sciences, Physical Sciences and Mathematics, Water Resource Management
This study presents an algorithm for the allocation of particulate phosphorus (PP) loads entering surface waters to their sources of origin, which is a basic requirement for the identification of critical PP source areas and in turn a cost-effective implementation of mitigation measures. Furthermore, it conducts a sensitivity analysis determining the impacts of storm drains, discharge frequencies [...]
A global hydrothermal reactor triggered prebiotic synthesis on Earth
Published: 2021-04-15
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Planetary Geology
Biosignatures in the rock record limit the time available for life to start on Earth to 600-800 million years1 (4.5-3.7 Ga; Hadean-Archean). Whether the conditions for the synthesis of complex organic molecules were unique to this time or remain present today is unclear, but understanding these conditions is essential for the search of life on other planets. The outer portion of the Hadean Earth [...]
Source region geochemistry from unmixing downstream sedimentary elemental compositions
Published: 2021-04-15
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
The geochemistry of river sediments is routinely used to obtain information about geologic and environmental processes occurring upstream. For example, downstream samples are used to constrain chemical weathering and physical erosion rates upstream, as well as the locations of mineral deposits or contaminant sources. Previous work has shown that, by assuming conservative mixing, the geochemistry [...]
Stress and Strain during Shock Metamorphism
Published: 2021-04-15
Subjects: Geology, Planetary Geology, Planetary Geophysics and Seismology, Tectonics and Structure
Shock metamorphism is the process by which rocks, and the minerals within them, transform during the passage of a shock wave. Shock effects, such as shatter cones, are critical for the identification of impact structures and have commonly been used to infer mechanical and structural information on the cratering process. To make these inferences, the mechanics of shock wave behavior must be [...]
Reactivation Potential of Intraplate Faults in the Western Quebec Seismic Zone, Eastern Canada
Published: 2021-04-19
Subjects: Earth Sciences, Physical Sciences and Mathematics
The intraplate western Quebec seismic Zone (WQSZ) in eastern Canada experiences moderate seismicity that mainly results from reactivation of inherited structures under the present-day, NE-striking regional stress field and, possibly to a minor extent, through stress perturbations in response to glacio-isostatic adjustments. This work comprises the first numerical stress simulation-based study [...]
Ongoing tectonic subsidence in the Lesser Antilles subduction zone
Published: 2021-04-20
Subjects: Earth Sciences
Geological estimates of vertical motions in the central part of the Lesser Antilles show subsidence on timescales ranging from 125.000 to 100 years, which has been interpreted to be caused by interseismic locking along the subduction megathrust. However, horizontal GNSS velocities show that the Lesser Antilles subduction interface is currently building up little to no elastic strain. Here we [...]
The Effect of Ti on Ca-pv and Mg-pv phase stability
Published: 2021-04-20
Subjects: Physical Sciences and Mathematics
Magnesium silicate perovskite in the form of bridgmanite (bdg) and Calcium silicate perovskite (Ca-pv) have similar chemical structures and may mix into a single perovskite phase in the lower mantle which would have profound effects on many seismic properties. While we have previously found that this is unlikely to occur in pure bdg and ca-pv in this paper we examine whether phase mixing can be [...]
Revision of thelodonts, acanthodians, conodonts, and the depositional environments in the Burgen outlier (Ludlow, Silurian) of Gotland, Sweden
Published: 2021-04-20
Subjects: Biodiversity, Earth Sciences, Ecology and Evolutionary Biology, Life Sciences, Physical Sciences and Mathematics
Ludfordian strata exposed in the Burgen outlier in eastern Gotland record a time of initial faunal recovery after a global environmental perturbation manifested in the Ludfordian Carbon Isotope Excursion (LCIE). Vertebrate microfossils in the collection of the late Lennart Jeppsson, hosted at the Swedish Museum of Natural History, hold the key to reconstruct the dynamics of faunal immigration and [...]
The 2019-2020 Southwest Puerto Rico earthquake sequence: seismicity and faulting
Published: 2021-04-20
Subjects: Geophysics and Seismology, Tectonics and Structure
The 2019-2020 Southwest Puerto Rico earthquake sequence ruptured multiple faults with several moderate magnitude earthquakes. Here we investigate the seismotectonics of this fault system using high precision hypocenter relocation and inversion of the near-field strong motions of five largest events in the sequence (5.6≤Mw≤6.4) for kinematic rupture models. The Mw6.4 mainshock occurred on an NE [...]
Impact and rebound of near real-time United States fossil fuel carbon dioxide emissions from COVID-19 and large differences with global estimates
Published: 2021-04-20
Subjects: Social and Behavioral Sciences
The COVID-19 pandemic has altered energy use and greenhouse gas (GHG) emissions globally and continues to evolve in the U.S. as the politics of COVID-19 change. Here we report on a new near-real-time fuel consumption data-driven, week-resolved estimate of national U.S. fossil fuel carbon dioxide (FFCO2) emissions, Vulcan-NRT. We explore the impact and rebound from the COVID-19 pandemic in the US. [...]
Comparison of Machine Learning Approaches for Tsunami Forecasting from Sparse Observations
Published: 2021-04-18
Subjects: Physical Sciences and Mathematics
We have explored various different machine learning (ML) approaches for forecasting tsunami amplitudes at a set of forecast points, based on hypothetical short-time observations at one or more observation points. As a case study, we chose an observation point near the entrance of the Strait of Juan de Fuca, and two forecast points in the Salish Sea, one in Discovery Bay and the other in Admiralty [...]