Geophysics and Seismology Commons^™

The Formation Of Distal Impact Ejecta, Brandon C. Johnson

Open Access Dissertations

Here we present two models for the dynamics of ejection and formation of distal impact ejecta. The first model focuses on the most highly shocked material that forms a massive expanding vapor plume or fireball. In this model molten droplets or spherules condense from the vapor. We model the expanding vapor plume using a one dimensional Lagrangian hydrocode. The condensation of droplets is treated by directly coupling the equations for homogeneous nucleation and growth with our hydrocode. The second model is focused on less energetic material ejected as part of the excavation flow. Using the iSALE hydrocode, we determine the …

Breaking Peroxy Bonds In H20 Ice Doped With H202 To Create Positive Hole Charge Carriers., Corey C. Stockburger

STAR Program Research Presentations

Using stress-activated electric conductivity in water ice doped with hydrogen peroxide as a model for stress-activated electric conductivity of igneous and high-grade metamorphic rocks due to the presence of peroxy defects, which when broken, createpositive-hole charge carriers. Blocks of pure H2O ice and H2O2–doped H2O ices, frozen at –20°C, will be stressed with piezo electric transducers(pzt) at one end to generate stress-activated electric currents flowing down the stress gradient. Pure H2O ice should produce no current or a small insignificant amount during rapid deformation or fracture. Stressing H2O2-doped H2O ices, however, should lead to 100-1000 times higher currents. These stress-activated …

Paleomagnetism And Investigation Of 40 Ma Lavas, Liverpool Range, New South Whales, Australia, Nathan M. Padilla

Physics

The main focus of this project is the continued study of a reversal of the earth’s magnetic field recorded from lavas in the Liverpool Range of New South Whales, Australia. This reverse-to-normal transition, recently dated at ~40 Ma, was first reported in Nature in 1986. [2] In March 2011 some 200+ cores were drilled from several sections about the volcanic range—Jemmy’s Creek, Bald Hill, Rock Creek, Yarraman, and Coolah Tops Road. Here we focus on paleomagnetic findings from samples drilled from the most extensive section, that being along the trail near Jemmy’s Creek. Results from alternating field demagnetization show the …

Exploring Methods For Earthquake Prediction: The Effects Of Water On The Flow Of Stress-Activated Electric Currents In Igneous Rocks, Aaron M. Jahoda, Friedemann T. Freund

STAR Program Research Presentations

Much of the devastation and damage of earthquakes can be attributed to the fact that they occur suddenly and without much warning, which limits the ability of people to evacuate and/or properly prepare. One method, however, that might be used to predict seismic events is the generation of electric currents in rocks when stresses are applied. It is observed in this research that the application of direct force onto samples of igneous rock causes the rocks to generate a measurable current, which is attributed to positive-hole charges moving within the oxygen sub-lattice. Because large and changing forces are acted upon …

Elastic Plastic Self Consistent (Epsc) Modeling Of Plastic Deformation In Fayalite Olivine, Christopher J. Cline Ii, Pamela Burnley

Festival of Communities: UG Symposium (Posters)

We are using an Elastic Plastic Self Consistent Model (a type of numerical simulation) to study deformation of olivine. Olivine is one of the major constituents of the Earth’s upper mantle and its deformation properties have an important influence on how the Earth’s crust deforms. For example, the flow strength of olivine limits the size of the largest earthquakes and the heights of the tallest mountains on Earth. By comparing the results of our simulations with data from olivine deformation experiments we are able to better interpret the experimental data.

Sensitivity Analysis Of Empirical Parameters In The Ionosphere-Plasmasphere Model, Janelle V. Jenniges

Theses and Dissertations

A sensitivity analysis of empirical parameters used in physics-based models was completed in this study to determine their effect on electron densities and total electron content (TEC) in the ionosphere. The model used was the Ionosphere-Plasmasphere Model (IPM) developed by Utah State University. The empirical parameters studied include the O⁺/O collision frequency, zonal wind, secondary electron production, nighttime ExB drifts, and tidal structure. The sensitivity analysis was completed by comparing a default run of the IPM to a run with the parameter adjusted for three geophysical cases. Many of the comparisons resulted in nonlinear changes to the model …

Kinematic And Dynamic Pair Collision Statistics Of Sedimenting Inertial Particles Relevant To Warm Rain Initiation, Bogdan Rosa, Hossein Parishani, Orlando Ayala, Lian-Ping Wang, Wojciech W. Grabowski

Engineering Technology Faculty Publications

In recent years, direct numerical simulation (DNS) approach has become a reliable tool for studying turbulent collision-coalescence of cloud droplets relevant to warm rain development. It has been shown that small-scale turbulent motion can enhance the collision rate of droplets by either enhancing the relative velocity and collision efficiency or by inertia-induced droplet clustering. A hybrid DNS approach incorporating DNS of air turbulence, disturbance flows due to droplets, and droplet equation of motion has been developed to quantify these effects of air turbulence. Due to the computational complexity of the approach, a major challenge is to increase the range of …

Towards An Integrated Multiscale Simulation Of Turbulent Clouds On Petascale Computers, Lian-Ping Wang, Orlando Ayala, Hossein Parishani, Wojciech W. Grabowski, Andrzej A. Wyszogrodzki, Zbigniew Piotrowski, Guang R. Gao, Chandra Kambhamettu, Xiaoming Li, Louis Rossi

Engineering Technology Faculty Publications

The development of precipitating warm clouds is affected by several effects of small-scale air turbulence including enhancement of droplet-droplet collision rate by turbulence, entrainment and mixing at the cloud edges, and coupling of mechanical and thermal energies at various scales. Large-scale computation is a viable research tool for quantifying these multiscale processes. Specifically, top-down large-eddy simulations (LES) of shallow convective clouds typically resolve scales of turbulent energy-containing eddies while the effects of turbulent cascade toward viscous dissipation are parameterized. Bottom-up hybrid direct numerical simulations (HDNS) of cloud microphysical processes resolve fully the dissipation-range flow scales but only partially the inertial …

Eastern Mediterranean Pore Waters: Clues Into The Geochemical Pathways From Evaporated Seawater To Basinal Brines, Jessica A. Mumphrey

Honors Capstones

No abstract provided.

Phonon Density Of States Of Iron Solid Solutions At Ambient And High Pressures Using Nuclear Inelastic X-Ray Scattering (Nrixs), Samantha L. Combs, Elizabeth A. Tanis, Malcolm Nicol

Undergraduate Research Opportunities Program (UROP)

Nuclear resonant inelastic x-ray scattering (NRIXS) of synchrotron radiation uses the energy transferred during the inelastic nuclear absorption of photons to determine phonon density of states for solid Mössbauer isotopes. This type of experiment can be conducted at ambient and high pressures with the use of a diamond anvil cell (DAC) and a rhenium gasket. Here, we are concerned with the phonon DOS of α-FePt 10% at pressures up to 30 GPa, as well as FeAl 4.3%, 6.4%, and 27.1% at ambient pressures. The iron samples used are doped in order to increase the pressure at which the alpha to …

Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston

CCPO Publications

Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the …

Auroral Ion Outflow: Low Altitude Energization, Kristina A. Lynch, J. L. Semeter, M. Zettergren, P. Kintner, R. Arnoldy, E. Klatt, J. Labelle, R. G. Michell

Dartmouth Scholarship

The SIERRA nightside auroral sounding rocket made observations of the origins of ion upflow, at topside F-region altitudes (below 700 km), comparatively large topside plasma densities (above 20 000/cc), and low energies (10 eV). Upflowing ions with bulk velocities up to 2 km/s are seen in conjunction with the poleward edge of a nightside substorm arc. The upflow is limited within the poleward edge to a region (a) of northward convection, (b) where Alfvenic ´ and Pedersen conductivities are well-matched, leading to good ionospheric transmission of Alfvenic power, and (c) of ´ soft electron precipitation (below 100 eV). Models of …

The Strange Physics Of Low Frequency Mirror Mode Turbulence In The High Temperature Plasma Of The Magnetosheath, R. A. Treumann, C. H. Jaroschek, O. D. Constantinescu, R. Nakamura

Dartmouth Scholarship

Mirror mode turbulence is the lowest frequency perpendicular magnetic excitation in magnetized plasma proposed already about half a century ago by Rudakov and Sagdeev (1958) and Chandrasekhar et al. (1958) from fluid theory. Its experimental verification required a relatively long time. It was early recognized that mirror modes for being excited require a transverse pressure (or temperature) anisotropy. In principle mirror modes are some version of slow mode waves. Fluid theory, however, does not give a correct physical picture of the mirror mode. The linear infinitesimally small amplitude physics is described correctly only by including the full kinetic theory and …

In Situ Stress, Fracture, And Fluid Flow Analysis In Well 38c-9: An Enhanced Geothermal System In The Coso Geothermal Field, Judith M. Sheridan, Stephen H. Hickman

United States Geological Survey: Staff Publications

Geoscientists from the Coso Operating Company, EGI-Utah, GeoMechanics International, and the United States Geological Survey are cooperating in a multi-year study to develop an Enhanced Geothermal System (EGS) in the Coso Geothermal Field. Key to the creation of an EGS is an understanding of the relationship among natural fracture distribution, fluid flow, and the ambient tectonic stresses that exist within the resource in order to design a hydraulic and thermal stimulation of an east-flank injection well, the first step in the creation of a heat exchanger at depth. Well datasets from the east flank of the Coso Geothermal Field are …

Chemical Signals From Submarine Fluid Advection Onto The Continental Shelf, W. S. Moore, Timothy J. Shaw

Faculty Publications

No abstract provided.

Geophysical Strain And Tilt: Measurement Methodology And Analysis Of Data, Robert Mackay

Dissertations and Theses

Tilt and strain meters were installed on the Portland State University campus in the summer of 1982 and data was collected for 4 months. Instrument selection, operation, installation and performance are discussed.

Suggestions that could enhance data quality and data collection efficiency are presented.

An analysis procedure is suggested and an example of this procedure for an interval of data is discussed. The influence of the temperature, pressure, rainfall and solid earth tides on the signal is investigated, as well as the correlation between similar channels of the different tilt instruments. The temperature, rainfall and solid earth tides were all …

On The Theory Of Head Waves, Patrick Heelan

Research Resources

When a combined longitudinal and transverse disturbance, diverging from a localized source, strikes a plane boundary between two solid elastic media, several systems of head waves and second order boundary waves are generated, each associated with grazing incidence of one or the other of the reflected or refracted waves. Associated with grazing incidence of P ₁ P₂, the refracted P-wave, is the head wave system comprising P₁P₂P₁ (the "refracted wave" of seismic prospectors), and P₁P₂S₁ (a transverse head wave) in the upper medium, and P₁P_{2 …}