Preprints
Filtering by Subject: Earth Sciences
Do Geology Field Courses Improve Penetrative Thinking?
Published: 2018-06-05
Subjects: Earth Sciences, Education, Geology, Physical Sciences and Mathematics
Spatial thinking skills are important for geoscientists, and field courses play an important role in using and developing those skills. This study examines the development of spatial perception and geoscience-specific penetrative thinking skills, as measured by paired pre- and post-tests using the water-level test and the Geologic Block Cross-sectioning Test, in a sophomore field mapping course. [...]
Insights into agricultural influences and weathering processes from major ion patters
Published: 2018-06-04
Subjects: Chemistry, Earth Sciences, Environmental Chemistry, Environmental Sciences, Geochemistry, Hydrology, Physical Sciences and Mathematics, Water Resource Management
Karst areas and their catchments pose a great challenge for protection because fast conduit flow results in low natural attenuation of anthropogenic contaminants. Studies of the hydrochemistry of karst sources and river solutes are an important tool for securing and managing water resources. A study of the geochemical downriver evolution of the Wiesent River and its tributaries, located in a [...]
Off-fault Focal Mechanisms not Representative of Interseismic Fault Loading Suggest Deep Creep on the Northern San Jacinto Fault
Published: 2018-06-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Within the San Bernardino basin, some focal mechanisms show normal slip that is inconsistent with the expected interseismic strike-slip loading of the region. The discrepancy may owe to deep (> 10 km depth), creep along the nearby northern San Jacinto fault. The enigmatic normal slip microseismicity occurs to the northeast of the fault and primarily below 10 km depth, consistent with off-fault [...]
Coulomb pre-stress and fault bends: ignored yet vital factors for earthquake triggering
Published: 2018-06-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Successive locations of individual large earthquakes (Mw>5.5) over years to centuries can be difficult to explain with simple Coulomb stress transfer (CST), because seismicity can miss out nearest-neighbour along-strike faults where coseismic CST increases are greatest. We show that “Coulomb pre-stress” may explain this, because magnitudes are >±50 bars if interseismic loading and local [...]
Micromorphological report of Tour Anneessens
Published: 2018-05-31
Subjects: Earth Sciences, Environmental Sciences, Geology, Physical Sciences and Mathematics, Soil Science, Stratigraphy
Micromorphological description of the thin sections retrieved from the Tour Anneesseens site (Brussels, Belgium)
The impact of earthquake cycle variability on neotectonic and paleoseismic slip rate estimates
Published: 2018-05-29
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Because of the natural variability (aleatoric uncertainty) in earthquake recurrence intervals and coseismic displacements on a fault, cumulative slip on a fault does not increase linearly or perfectly step-wise with time; instead, some amount of variability in shorter-term slip rates results. Though this variability could greatly affect the accuracy of neotectonic (i.e., late Quaternary) and [...]
Origin and time evolution of subduction polarity reversal from plate kinematics of Southeast Asia
Published: 2018-05-28
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
We present a regional model of plate geometry and kinematics of southeast Asia since the Late Cretaceous, embedded in a global plate model. The model involves subduction polarity reversals and sheds new light on the origin of the subduction polarity reversal presently observed in Taiwan. We show that this subduction zone reversal is inherited from subduction of the Proto South China Sea plate and [...]
Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation
Published: 2018-05-28
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics, Volcanology
Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid‐filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a [...]
Crack models of repeating earthquakes predict observed moment-recurrence scaling
Published: 2018-05-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Small repeating earthquakes are thought to represent rupture of isolated asperities loaded by surrounding creep. The observed scaling between recurrence interval and seismic moment, Tr ~ M^(1/6), contrasts with expectation assuming constant stress drop and no aseismic slip (Tr ~ M^(1/3)). Here we demonstrate that simple crack models of velocity-weakening asperities embedded in a [...]
Pervasive iron limitation at subsurface chlorophyll maxima of the California Current
Published: 2018-05-24
Subjects: Biogeochemistry, Earth Sciences, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Subsurface chlorophyll maximum layers (SCMLs) are nearly ubiquitous in stratified water columns and exist at horizontal scales ranging from the submesoscale to the extent of oligotrophic gyres. These layers of heightened chlorophyll and/or phytoplankton concentrations are generally thought to be a consequence of a balance between light energy from above and a limiting nutrient flux from below, [...]
Time scales of shallow magma chamber replenishment at Campi Flegrei caldera.
Published: 2018-05-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Ascent of primitive magmas from depth into shallow, partially degassed reservoirs is commonly assumed to be a viable eruption trigger. The resulting processes of convection and mixing have played an important role both in pre- and syn-eruptive stages in many eruptions of different sizes at the unrest Campi Flegrei caldera in Southern Italy. We performed numerical simulations of magma chamber [...]
The effects of differential compaction on clinothem geometries and shelf-edge trajectories
Published: 2018-05-23
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
The geometry of basin margin strata documents changes in water depth, slope steepness, and sedimentary facies distributions. Their stacking patterns are widely used to define shelf-edge trajectories, which reflect long-term variations in sediment supply and relative sea level change. Here, we present a new method to reconstruct the geometries and trajectories of clinoform-bearing basinmargin [...]
Experimental and Geochemical Modeling Evidences of Mineral Sequestration of CO2 in Saline Siliciclastic aquifers
Published: 2018-05-23
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
The validity of mineral sequestration in saline siliciclastic aquifers in sedimentary basins is assessed in this paper. Mineral sequestration is the precipitation of carbonates due to the dissolution of silicates upon the injection of CO2 in deep geological formations, while solubility trapping is the dissolution of CO2 in the formation water. Saline reservoirs in sedimentary basins seem to [...]
Towards a global interpretation of dual nitrate isotopes in natural water
Published: 2018-05-23
Subjects: Biogeochemistry, Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Sciences, Physical Sciences and Mathematics, Water Resource Management
Modern anthropogenic activities have significantly increased nitrate (NO3-) concentrations in surface waters. Stable isotopes (δ15N and δ18O) in NO3- offer a tool to deconvolute some of the human-made changes in the nitrogen cycle. They are often graphically illustrated on a template designed to identify different sources of NO3- and denitrification. In the two decades since this template was [...]
Geophysical Investigations of WW2 UK air-raid shelters
Published: 2018-05-22
Subjects: Earth Sciences, Other Earth Sciences, Physical Sciences and Mathematics
Just before WW2, the British government prepared for an aerial onslaught that was predicted to raze cities and cause mass casualties. By 1938, the Air Raid Precautions Act officially stated that population protection would be through dispersal, meaning evacuation and small-scale protection, local authority responsibility often devolving to householders. Archaeological records of remaining [...]