Geophysics and Seismology Commons^™

Physical Modeling And Analysis Of P-Wave Attenuation Anisotropy, Kasper Van Wijk

CGISS Publications and Presentations

Anisotropic attenuation can provide sensitive attributes for fracture detection and lithology discrimination. This paper analyzes measurements of the P-wave attenuation coefficient in a transversely isotropic sample made of phenolic material. Using the spectral-ratio method, we estimate the group (effective) attenuation coefficient of P-waves transmitted through the sample for a wide range of propagation angles (from 0° to 90°) with the symmetry axis. Correction for the difference between the group and phase angles and for the angular velocity variation help us to obtain the normalized phase attenuation coefficient A governed by the Thomsen-style attenuation-anisotropy parameters ε_Q and δ_Q. …

Integrated Geophysical Data Processing And Interpretation Of Crustal Structure In Ethiopia With Emphasis On The Ogaden Basin And Adjacent Areas, Ketsela Tadesse

Open Access Theses & Dissertations

The combined effects of magmatism and stretching due to asthenosphere upwelling modifies the crustal structure of the Earth as seen in the Ethiopian rift and adjacent areas. The Ethiopian rift provides unique opportunities to understand the nature of rifted crust and the intensity of its modification by magmatic processes. I used geological and geophysical data to conduct an integrated study in and around the Ethiopian rift including the northern Kenyan rift and the northern part of the Kenyan dome. New gravity, controlled source seismic, and teleseismic data from the EAGLE (Ethiopia-Afar Geoscientific Lithospheric Experiment) were used as additional constraints in …

Seismic Constraints On Slow Slip Events Within The Cascadia Subduction Zone, Ana Cristina Aguiar

All Master's Theses

Reanalysis of geodetic GPS time series from the Cascadia subduction zone have revealed at least 30 resolvable slow slip events along the megathrust, ranging from northern California to southern British Columbia, since 1997. Many of the smaller and more recent events are barely resolvable with GPS, but stand out clearly as tremor sequences. Since tremor bursts lasting less than 10-seconds are often visible across multiple stations, they offer the highest resolution for studying moment release through time. To test the hypothesis that tremor and transient deformation are two manifestations of the same faulting process, and to quantify the relative contribution …

Late Holocene Uplift Of The Chihshang Segment Of The Longitudinal Valley Fault At Fuli, Eastern Taiwan, Brian Thomas Gray

All Master's Theses

Uplifted Holocene strath terraces of the Bieh River drainage, eastern Taiwan, were analyzed in order to determine millennial-scale uplift and horizontal shortening rates of the Longitudinal Valley fault. Detrital charcoal fragments collected from three terraces within the Bieh River drainage yield ages between 1395 and 555 cal. yr B.P, suggesting an average uplift rate of 11.3 ± 3.6 mm yr^-1 for the last 1400 cal. yr B.P. The average horizontal shortening rate of 19.7 ± 9.5 mm yr^-1 was within error of present-day conventional geodetic measurements, but near the lower limit of the geodetic measurements. This suggests that …

Incipient Continental Rifting: Insights From The Okavango Rift Zone, Northwestern Botswana, Baraka D. Kinabo

Doctoral Dissertations

"In this dissertation aeromagnetic, gravity, and Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) data from the Okavango Rift Zone in northwest Botswana are used to map the distribution of rift and basement structures. The distribution of these structures provide useful insights into the early stages of continental rifting. The objectives of this study are (1) assessing the role of pre-existing structures on rift basin development, (2) characterizing the geometry of the nascent rift basins, (3) documenting fault growth and propagation patterns, and (4) investigating the border fault development"--Abstract, page iv.

An Investigation Of Lead And Other Metal Contaminants In The Sediments Of Clearwater Lake, Missouri, Gary W. Krizanich

Doctoral Dissertations

"The purpose of this investigation is to characterize the spatial and temporal distribution and concentration of trace metals in sediments of Clearwater Lake. Understanding how trace metals are released to and transported in aquatic environments is important to the overall understanding of the impacts of mining on the natural environment. The main focus of this research will be on historic sedimentation within Clearwater Lake, which may act as a sink where mining related trace metals are stored. Because of their high preservation rates in basins, sediments can provide detailed chronostratigraphic histories of trace metal inputs in lakes. Sediment records can …

Impacts Of Acid Mine Drainage On Carbon Cycling In Receiving Streams, Ernest W. Fonyuy

Doctoral Dissertations

"Field and laboratory investigations of acid mine drainage (AMD) contaminated and uncontaminated waters were conducted in order to determine and model processes and reaction mechanisms that control dissolved inorganic carbon (DIC) transformation and shifts in isotope ratio of DIC (Δ¹³C_DIC). The results show that AMD caused variable pH changes, overall decreases in Fe²⁺, alkalinity, and DIC, and increases in (Δ¹³C_DIC) in receiving streams. AMD caused more than 50 to > 98% seasonal DIC loss in stream water through CO₂ degassing. High DIC losses corresponded to high Fe²⁺ and lower or no HCO₃⁻ in the water samples, because …

Issues During The Inversion Of Crosshole Radar Data: Can We Have Confidence In The Outcome?, William P. Clement

Geosciences Faculty Publications and Presentations

One method of assessing the confidence in modeled features is to compare the results from different inversion schemes. I use synthetic traveltimes calculated from a model of an unconfined aquifer to determine the reliability of crosshole tomography. I compare the inverted models from straight and curved ray approximations to wave propagation. I investigate the effects of added random noise, regularization, the starting model, and the reference model on the curved ray inversion method. I also investigate the effects of different grid sizes for the forward model and of limited ray coverage through the earth model. Understanding the effects of these …

Geogram 2006, David J. Keeling Editor, Wku Department Of Geography And Geology

Earth, Environmental, and Atmospheric Sciences Publications

No abstract provided.

Precarious Rock Methodology For Seismic Hazard: Physical Testing, Numerical Modeling, And Coherence Studies, Rasool Anooshehpoor, James N. Brune, Amy J. Smiecinski, Raymond E. Keeler

Publications (YM)

The precarious rock methodology used for seismic hazard assessment includes location, age dating, field measurements of the quasi-static toppling acceleration of balanced rocks, and study of their dynamic response to realistic strong motion seismograms using numerical modeling. The work scope is contained in the task description issued by the DOE to the Seismology Laboratory of the University of Nevada, Reno and is itemized in section 2.3 below. In addition, measurement of the coherence of seismic energy at high frequencies, critical to the understanding of the variability of high frequency ground motions at the repository level, will be estimated based on …

Imaging Complex Structure In Shallow Seismic-Reflection Data Using Prestack Depth Migration, John H. Bradford, Lee M. Liberty, Mitchell W. Lyle, William P. Clement, Scott Hess

CGISS Publications and Presentations

Prestack depth migration (PSDM) analysis has the potential to significantly improve the accuracy of both shallow seismic reflection images and the measured velocity distributions. In a study designed to image faults in the Alvord Basin, Oregon, at depths from 25–1000 m, PSDM produced a detailed reflection image over the full target depth range. In contrast, poststack time migration produced significant migration artifacts in the upper 100 m that obscured reflection events and limited the structural interpretation in the shallow section. Additionally, an abrupt increase from ~2500 to >3000 m/s in the PSDM velocity model constrained the interpretation of the transition …

Crosshole Radar Tomography In A Fluvial Aquifer Near Boise, Idaho, William P. Clement, Warren Barrash

Geosciences Faculty Publications and Presentations

To determine the distribution of heterogeneities in the saturated zone of an unconfined aquifer in Boise, ID, we compute tomograms for three adjacent well pairs. The fluvial deposits consist of unconsolidated cobbles and sands. We used a curved-ray, finite-difference approximation to the eikonal equation to generate the forward model. The inversion uses a linearized, iterative scheme to determine the slowness distribution from the first arrival traveltimes. The tomograms consist of a layered zone representing the saturated aquifer. The velocities in this saturated zone range between 0.06 to 0.10 m/ns. We use a variety of methods to assess the reliability of …

Precarious Rock Methodology For Seismic Hazard: Physical Testing, Numerical Modeling And Coherence Studies, Rasool Anooshehpoor, Matthew D. Purvance, James N. Brune, Leiph A. Preston, John G. Anderson, Ken Smith, Amy J. Smiecinski

Publications (YM)

This report covers the following projects: Shake table tests of precarious rock methodology, field tests of precarious rocks at Yucca Mountain and comparison of the results with PSHA predictions, study of the coherence of the wave field in the ESF, and a limited survey of precarious rocks south of the proposed repository footprint. A series of shake table experiments have been carried out at the University of Nevada, Reno Large Scale Structures Laboratory. The bulk of the experiments involved scaling acceleration time histories (uniaxial forcing) from 0.1g to the point where the objects on the shake table overturned a specified …

Sinkhole Structure Imaging In Covered Karst Terrain, Sarah E. Kruse, M. Grasmueck, Matthew Weiss, D. Viggiano

Geology Faculty Publications

Ground penetrating radar (GPR) and resistivity techniques have been widely used to map the locations of sinkholes in covered karst terrain. To determine whether a sinkhole is a likely preferential conduit for groundwater flow, however, requires higher-resolution imaging than that used in conventional sinkhole mapping surveys. Field observations combined with simulated surveys for a 15-m diameter 3-m deep sinkhole in west-central Florida are used to assess the resolution of GPR and resistivity surveys targeting the semiconfining unit that floors the sinkhole depression. 2D resistivity surveys clearly show the central depression as well as resistivity contrasts between the cover sediments within …

Maximum A Posteriori Resampling Of Noisy, Spatially Correlated Data, John A. Goff, Chris Jenkins, Brian R. Calder

Center for Coastal and Ocean Mapping

In any geologic application, noisy data are sources of consternation for researchers, inhibiting interpretability and marring images with unsightly and unrealistic artifacts. Filtering is the typical solution to dealing with noisy data. However, filtering commonly suffers from ad hoc (i.e., uncalibrated, ungoverned) application. We present here an alternative to filtering: a newly developed method for correcting noise in data by finding the “best” value given available information. The motivating rationale is that data points that are close to each other in space cannot differ by “too much,” where “too much” is governed by the field covariance. Data with large uncertainties …

Extreme Ground Motion Studies, John G. Anderson, James N. Brune, Amy J. Smiecinski, Raymond E. Keeler

Publications (YM)

This project consists of two separate investigations into extreme ground motions due to seismic events. First, it includes field studies of geological formations that should put an upper bound on extreme ground motions that have happened at the site of the formations. The locations are critically selected to provide the most effective constraints possible on the validity of the probabilistic seismic hazard analysis for Yucca Mountain. Second, this project surveys recorded ground motions from around the world, and aims to draw general conclusions from these as to the conditions where extreme ground motions are observed.

Ground-Penetrating Radar Theory And Application Of Thin-Bed Offset-Dependent Reflectivity, John H. Bradford, Jacob C. Deeds

CGISS Publications and Presentations

Offset-dependent reflectivity or amplitude-variationwith- offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ …

Reflectivity Modeling Of A Ground-Penetrating-Radar Profile Of A Saturated Fluvial Formation, William P. Clement, Warren Barrash, Michael D. Knoll

Geosciences Faculty Publications and Presentations

Major horizons in radar reflection profiles may correlate with contacts between stratigraphic units or with structural breaks such as fault surfaces. Minor reflections may be caused by clutter or, in some cases, may indicate material properties or structure within stratigraphic units. In this study, we examine the physical basis for major and minor reflections observed in a shallow, unconfined, fluvial aquifer near Boise, Idaho, U. S. A. We compare a 2D profile from a surface ground-penetrating-radar reflection transect with the 1D modeled reflection profiles at three wells adjacent to the surface-reflection profile. The 1D models are based on dielectric constant …

Investigating The Stratigraphy Of An Alluvial Aquifer Using Crosswell Seismic Traveltime Tomography, Geoff J.M. Moret, Michael D. Knoll, Warren Barrash, William P. Clement

CGISS Publications and Presentations

In this study, we investigate the use of crosswell P-wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers. Our field site was a research wellfield in an unconfined aquifer near Boise, Idaho. The aquifer consists of a ~ 20-m-thick sequence of alluvial cobble- and-sand deposits, which have been subdivided into five stratigraphic units based on neutron porosity logs, grainsize analysis, and radar reflection data. We collected crosswell and borehole-to-surface seismic data in wells 17.1 m apart. We carefully considered the impact of well deviation, data quality control, and the choice of inversion …

Traveltime Inversion Of Vertical Radar Profiles, William P. Clement, Michael D. Knoll

Geosciences Faculty Publications and Presentations

Traveltimes of direct arrivals in vertical radar profiles (VRPs) are tomographically inverted to estimate the earth’s electromagnetic (EM) velocity between a surface transmitter and a downhole receiver. We determine the 1D interval velocity model that best fits the first-arrival traveltimes by using a weighted, damped, least-squares inversion scheme. We assess the accuracy of the velocity model using synthetic traveltimes from a known velocity-distribution model simulating an unconfined aquifer. The inverted velocity profile closely matched the velocity profile of the input model in the synthetic examples. Using vertical radar profile data from an unconfined aquifer near Boise, Idaho, we inverted traveltimes …

2nd Annual Undergraduate Research Conference Abstract Book, University Of Missouri--Rolla

Undergraduate Research Conference at Missouri S&T

No abstract provided.

Image Interpretation Using Appraisal Analysis, Partha S. Routh, Carlyle R. Miller

Geosciences Faculty Publications and Presentations

In geophysical inversion, a significant effort is invested to obtain images of the Earth from finite data. The first step is to obtain an image i.e. solve the inverse problem. This step alone provides significant challenges that are not addressed inthis paper. The next step is to interpret the image in terms of specific questions. For example, what can we say about the average value of a physical property within a certain region of the model? What scale information can we resolve from the data? These questions are problem dependent and may require that inversion be carried out several times …

Thermometric Measurements Of The Molecular Sublayer At The Air-Water Interface, B. Ward

OES Faculty Publications

[1] A series of measurements was conducted in the AirSea Interaction Saltwater Tank (ASIST) to study the response of the air-water interfacial molecular sublayer under various heat flux and wind speed conditions. In-situ gradients were measured with a platinum-plated tungsten wire microthermometer, which resolved the temperature of the thermally conductive sublayer. Air-sea heat flux was controlled by changing the air-water temperature difference (ΔT^AW) and the wind speed, and measurements were made for three ΔT^AW regimes over a range of wind speeds. A function was fitted to the measured temperature profiles as a way of extracting the boundary …

Serial Ruptures Of The San Andreas Fault, Carrizo Plain, California, Revealed By Three-Dimensional Excavations, Jing Liu-Zeng, Yann Klinger, Kerry Sieh, Charles Rubin, Gordon Seitz

All Faculty Scholarship for the College of the Sciences

It is poorly known if fault slip repeats regularly through many earthquake cycles. Well‐documented measurements of successive slips rarely span more than three earthquake cycles. In this paper, we present evidence of six sequential offsets across the San Andreas fault at a site in the Carrizo Plain, using stream channels as piercing lines. We opened a latticework of trenches across the offset channels on both sides of the fault to expose their subsurface stratigraphy. We can correlate the channels across the fault on the basis of their elevations, shapes, stratigraphy, and ages. The three‐dimensional excavations allow us to locate accurately …

Applying Reflection Tomography In The Postmigration Domain To Multifold Ground-Penetrating Radar Data, John H. Bradford

CGISS Publications and Presentations

Acquisition and processing of multifold ground-penetrating radar (GPR) data enable detailed measurements of lateral velocity variability. The velocities constrain interpretation of subsurface materials and lead to significant improvement in image accuracy when coupled with prestack depth migration (PSDM). Reflection tomography in the postmigration domain was introduced in the early 1990s for velocity estimation in seismic reflection. This robust, accurate method is directly applicable in multifold GPR imaging. At a contaminated waste facility within the U.S. Department of Energy’s Hanford site in Washington, the method is used to identify significant lateral and vertical velocity heterogeneity associated with infilled waste pits. Using …

Guide To Participation For The Andrill Mcmurdo Ice Shelf Project, Andrill Science Management Office, Mcmurdo-Andrill Science Implementation Committee

ANDRILL Project Information

Purpose of This Document

This document is a guide to participation for science team members involved in the McMurdo Ice Shelf (MIS) Project of the ANDRILL Program. The document provides the following information: 1) An overview of the ANtarctic geologic DRILLing (ANDRILL) Program; 2) An overview of expected individual involvement in and commitment to the MIS Project; and 3) Logistical information most relevant to on-ice participants. Information provided in this document will be supplemented by the publication of the MIS Science and Logistics Implementation Plan (SLIP).The SLIP will be available to all MIS ANDRILL participants prior to commencement of drilling. …

Seeing Through The Noise: Seismic Reflection Profiling In Urban Areas, Lee M. Liberty, Thomas L. Pratt, Scott S. Hess

CGISS Publications and Presentations

Studies for urban hazard or resource assessment often take place in densely populated areas characterized by considerable cultural noise. These site conditions can severely compromise seismic reflection data quality. We have collected vibroseis and hammer (weight drop) seismic reflection data in a range of geologic conditions to image stratigraphy and structures in the upper one km along regional highways, city streets,and power line access roads. In addition to the challenges of safety and outreach, acquisition efforts along busy streets and highways often encounter poor receiver coupling and large-amplitude coherent noise from traffic and power lines. Although higher quality seismic reflection …

Cave Levels, Marine Terraces, Paleoshorelines, And The Water Table In Peninsular Florida, Lee J. Florea, H L. Vacher

Earth, Environmental, and Atmospheric Sciences Faculty Publications

Levels of passages are a common feature of many cave systems around the world. Likewise, coastal and marine terraces are common in coastal plain settings. This paper extends the discussion of cave levels from traditional research sites in the interior lowlands of the United States to the Atlantic Coastal Plains, namely peninsular Florida. Are there levels in Florida caves, and is there a link between the elevation of cave levels, marine terraces, paleoshorelines, and thus the water table, above and below present sea level in peninsular Florida?

Crosshole Radar Tomography In An Alluvial Aquifer Nearboise, Idaho, William P. Clement, Warren Barrash

CGISS Publications and Presentations

To determine the distribution of heterogeneities in an unconfined aquifer in Boise, ID, we compute radar tomograms for three adjacent well pairs. The fluvial deposits consist of unconsolidated cobbles and sands. We used a curved‐ray, finite‐difference approximation to the eikonal equation to generate the forward model. The inversion uses a linearized, iterative scheme to determine the slowness distribution from the first arrival traveltimes. The tomograms consist of a sequence of layers representing the saturated aquifer. The velocities in this saturated zone range between 0.06 to 0.10 m/ns. We use a variety of methods to assess the reliability of our velocity …

Relating Damping To Soil Permeability, Paul Michaels

CGISS Publications and Presentations

Published comparisons of complex moduli in dry and saturated soils have shown that viscous behavior is only evident when a sufficiently massive viscous fluid (like water) is present. That is, the loss tangent is frequency dependent for water saturated specimens, but nearly frequency independent for dry samples. While the Kelvin-Voigt (KV) representation of a soil captures the general viscous behavior using a dashpot, it fails to account for the possibly separate motions of the fluid and frame (there is only a single mass element). An alternative representation which separates the two masses, water and frame, is presented here. This Kelvin-Voigt-Maxwell-Biot …