Earth Sciences Commons^™

Wave Field Migration As A Tool For Estimating Spatially Continuous Radar Velocity And Water Content In Glaciers, John H. Bradford, Joel T. Harper

CGISS Publications and Presentations

Normal-moveout velocity analysis can lead to significant overestimates of the velocity structure of temperate glaciers since most englacial reflectors approximate point scatters and violate the assumption of planar flat lying reflectors. Migration velocity analysis (MVA) is a tool that does not depend on the assumption of flat lying reflectors. MVA can provide laterally and vertically continuous velocity estimates from conventional common-offset radar sections. In a study of temperate Bench Glacier, Alaska, we used MVA coupled with dielectric modeling to estimate the distribution of water content along a cross-section of the glacier. We found the glacier has two layers, an upper …

Effects Of Signal Processing And Antenna Frequency On The Geostatistical Structure Of Ground-Penetrating Radar Data, Greg A. Oldenborger, Michael D. Knoll, Warren Barrash

CGISS Publications and Presentations

Recent research has suggested that the geostatistical structure of ground-penetrating radar data may be representative of the spatial structure of hydraulic properties. However, radar images of the subsurface can change drastically with application of signal processing or by changing the signal frequency. We perform geostatistical analyses of surface radar reflection profiles in order to investigate the effects of data processing and antenna frequency on the semivariogram structure of radar reflection amplitudes. Surface radar reflection data collected at the Boise Hydrogeophysical Research Site illustrate the processing- and antenna-dependence of radar semivariograms for a fluvial, cobble-and-sand aquifer. Compensating for signal attenuation and …

Seismic Expression Of Pleistocene Paleoceanographic Changes In The California Borderland From Digitally Acquired 3.5 Khz Subbottom Profiles And Ocean Drilling Program Leg 167 Drilling, Aleksandra Janik, Mitchell W. Lyle, Lee M. Liberty

CGISS Publications and Presentations

We correlate processed 3.5 kHz seismic profiles with physical properties of cores collected during ODP Leg 167 from the Tanner, East Cortes, and San Nicolas Basins through much of the Pleistocene succession. Results indicate that seismic horizons in the unconsolidated Pleistocene sediments (top 50 m) are mainly controlled by density contrasts. Removing of the compaction trend from the density reveals a very interesting relationship between density and composition - the density closely and inversely correlates with organic carbon indicating that large-scale variations in organic carbon are responsible for seismic reflections through their influence on density. This is a significant discovery …

Vsp Traveltime Inversion: Near-Surface Issues, Geoff J. M. Moret, William P. Clement, Michael D. Knoll, Warren Barrash

Geosciences Faculty Publications and Presentations

P-wave velocity information obtained from vertical seismic profiles (VSPs) can be useful in imaging subsurface structure, either by directly detecting changes in the subsurface or as an aid to the interpretation of seismic reflection data. In the shallow subsurface, P-wave velocity can change by nearly an order of magnitude over a short distance, so curved rays are needed to accurately model VSP traveltimes. We used a curved-ray inversion to estimate the velocity profile and the discrepancy principle to estimate the data noise level and to choose the optimum regularization parameter. The curved-ray routine performed better than a straight-ray inversion for …

Multivariate Analysis Of Cross-Hole Georadar Velocity And Attenuation Tomograms For Aquifer Zonation, Jens Tronicke, Klaus Holliger, Warren Barrash, Michael D. Knoll

CGISS Publications and Presentations

We have investigated the potential of combining cross-hole georadar velocity and attenuation tomography as a method for characterizing heterogeneous alluvial aquifers. A multivariate statistical technique, known as k-means cluster analysis, is used to correlate and integrate information contained in velocity and attenuation tomograms. Cluster analysis allows us to identify objectively the major common trends in the tomographic data and thus to ‘‘reduce’’ the information to a limited number of characteristic parameter combinations. The application of this procedure to two synthetic data sets indicates that it is a powerful tool for converting the complex relationships between the tomographically derived velocity …

Mae Sae Basin And Wiang Nong Lom: Radiocarbon Dating And Relation To The Active Strike-Slip Mae Chan Fault, Northern Thailand, Spencer H. Wood, Fongsaward S. Singharajwarapan, Tharaporn Bundarnsin, Eric Rothwell

Geosciences Faculty Publications and Presentations

The Mai Sai basin and the Wiang Nong Lom swamp lie north of, and adjacent to, the northeast-trending Mae Chan fault, which is a left -lateral strike-slip fault in northernmost Thailand. The sediment in the Mae Sai basin is about 600 meters thick. The Mae Sai basin has an anticlinal fold below a 390-meter depth. This fold is buried by broadly downwarped sediment. In the Wiang Nong Lom swamp, sediment is about 170 meters thick. Radiocarbon ages from a 2.7-meter auger hole at Ko Mae Mai in the Wiang Nong Lom swamp show that 0.5 meter of sediment accumulated in …

Design Of Geophysical Surveys In Transportation, Paul Michaels

CGISS Publications and Presentations

Designing geophysical investigations for transportation related projects requires special attention to the constraints imposed by right-of-way, irregular topography, noise from traffic, and the need to avoid the interruption of traffic flow. A geophysical engineer needs to be prepared to consider these design issues that are not addressed in a standard procedure such as ASTM D-5777. The author presents design strategies that address these issues, and illustrates the concepts with case histories taken from bridge and highway projects. Beam steering, broadside shooting, and non-traditional designs that preserve alternative analysis options are presented. Transportation engineers who augment traditional subsurface geotechnical surveys with …

Terminal Moraine Remnants Of The Trail Creek Glacier Northeast Of Sun Valley, Idaho, Eric L. Rothwell, Spencer H. Wood

Geosciences Faculty Publications and Presentations

This optional excursion is 8 miles on paved road from the center of Ketchum (Main Street and Sun Valley Road traffic light), northeast through Sun Valley along the Trail Creek Road (fig. 1). A short walk of 10 minutes takes you to the crests of two moraines of very different ages. Here we view and discuss calcareous soils developed into the deposits, the pretty weathering-rinds developed on the sandstone cobbles, and ages of Pinedale and Bull Lake advances. During the Quaternary, an extensive system of mountain glaciers accumulated in the Pioneer and Boulder Mountains and flowed down valleys emanating from …

Geology Across And Under The Western Snake River Plain, Idaho: Owyhee Mountains To The Boise Foothills, Spencer H. Wood

Geosciences Faculty Publications and Presentations

This 1-day field trip is a transect across the western Snake River Plain (fig. 1). The western plain is a continental- rift structure, 300 km long and 70 km wide. It is bounded and internally faulted by northwest-trending normal faults. The western Snake River Plain has a different orientation and structure than the eastern plain. The eastern plain is a curious downwarp related to magmatism and extension along the track of the Yellowstone hot spot (fig. 2). The faulted basin of the western plain began forming about 12 m.y. ago, and much of the relief was completed by 9 Ma. …

Fire And Ice In Central Idaho: Modern And Holocene Fires, Debris Flows, And Climate In The Payette River Basin, And Quaternary And Glacial Geology In The Sawtooth Mountains, Jennifer L. Pierce, Grant A. Meyer, Glenn D. Thackray, Spencer H. Wood, Kari Lundeen, Jennifer A. Borgert, Eric Rothwell

Geosciences Faculty Publications and Presentations

This 2-day trip will highlight recent fire and storm-related debris flows in the Payette River region, Holocene records of fires and fire-related sedimentation events preserved in alluvial fan stratigraphic sequences, and geomorphology and geology of alpine glaciations in the spectacular Sawtooth Mountains and Stanley Basin of central Idaho. Storm events and associated scour following recent fires in the South Fork Payette basin have exposed Holocene fire-related debris-flow deposits, flood sediments, and other alluvial fan-building deposits that yield insights into Holocene environmental change. Moraine characteristics and sediment cores from the southeastern Sawtooth Mountains and Stanley Basin provide evidence of late Pleistocene …

Recent Paleoseismic Investigations In Northern And Western Thailand, Clark H. Fenton, Punya Charusiri, Spencer H. Wood

Geosciences Faculty Publications and Presentations

Recent paleoseismic investigations have identified a number of active faults in Northern and Western Thailand. Northern Thailand is an intraplate basin and range province, comprised of north-south-trending Cenozoic intermontane grabens and half grabens, bounded by north- to northwest-striking normal to normal-oblique faults and northeast-striking left-lateral strike-slip faults. The basin-bounding normal faults are marked by steep, linear range fronts with triangular facets and wineglass canyons and have slip rates of 0.1 to 0.8 mm/yr. Based on limited data, the average vertical displacement-per-event is about 1.0 to 1.5 m. These faults are characterized by recurrence intervals of thousands to tens of thousands …

Lower Miocene To Present Stratigraphy Of The Equatorial Pacific Sediment Bulge And Carbonate Dissolution Anomalies, Neil C. Mitchell, Mitchell W. Lyle, Marie B. Knappenberger, Lee M. Liberty

CGISS Publications and Presentations

The bulge is a 600-m-thick regional deposit of pelagic sediment accumulated around the equator. Its stratigraphy reflects a number of factors: how accumulation rates have varied over time, how accumulation has been spatially focused around the equator, how much carbonate dissolution and reworking or nondeposition by bottom currents have occurred, and how much the deposits have been translated northward by motion of the Pacific tectonic plate on which they have accumulated. In order to fully explore the effects of these processes, a spatially continuous stratigraphic database is desirable, as existing cores provide information at only discrete points, and they tend …

Tracer/Time-Lapse Radar Imaging Test At The Boise Hydrogeophysical Research Site, Warren Barrash, Michael D. Knoll, David W. Hyndman, Tom Clemo, Edward C. Reboulet, Elisabeth M. Hausrath

Geosciences Faculty Publications and Presentations

A combined tracer and time-lapse radar imaging experiment was conducted in the unconfined coarse fluvial aquifer at the Boise Hydrogeophysical Research Site in August, 2001. Two tracers (bromide and uranine) were injected to form a plume over a 4-m interval that spanned the contact between hydrostratigraphic units with contrasting permeability. The tracer plume traveled 6.9 m to well B6, passing through well A1 instrumented with 20 sampling zones over a 5-m interval that spanned the injection interval. Radar tomographic data were collected periodically on cross-sectional and longitudinal planes, two of which passed through well A1 for quantitative calibration of radar …

Borehole Radar Attenuation-Difference Tomography During The Tracer/Time-Lapse Test At The Boise Hydrogeophysical Research Site, Sarah E. Goldstein, Tim C. Johnson, Michael D. Knoll, Warren Barrash, William P. Clement

Geosciences Faculty Publications and Presentations

A tracer test and time-lapse radar imaging experiment was conducted at the Boise Hydrogeophysical Research Site to investigate the utility of crosswell radar in imaging an electrically conductive tracer plume. A multilevel water sampling system down gradient from the tracer injection well and in the radar imaging plane was used to collect detailed, 1-dimensional, fluid electrical conductivity data during the tracer test. We compare the spatial and temporal position and concentration variations of the plume as indicated by the fluid conductivity data to those suggested by radar level run attenuation differences, shot-receiver attenuation difference crossplots, and an attenuation-difference tomogram. We …

Hierarchical Geostatistics And Multifacies Systems: Boise Hydrogeophysical Research Site, Boise, Idaho, Warren Barrash, Tom Clemo

CGISS Publications and Presentations

The geostatistical structure of a heterogeneous coarse fluvial aquifer is investigated with porosity data derived from neutron logs at a research well field (Boise Hydrogeophysical Research Site, or BHRS) that was designed, in part, to support three-dimensional geostatistical analysis of hydrologic and geophysical parameters. Recognizing that the coarse fluvial deposits include subdivisions (units between bounding surfaces), we adopt a hierarchical approach and examine the porosity geostatistics of the aquifer at three scales. At the BHRS, the saturated fluvial deposits as a whole (maximum interwell spacing ~80 m, thickness ~16–18 m) are at hierarchical level 1; five subhorizontal units within these …

Equatorial Ocean Circulation In An Extremely Warm Climate, T. C. Moore, D. K. Rea, Mitchell W. Lyle, Lee M. Liberty

CGISS Publications and Presentations

The warm climates of the early Paleogene and the associated diminished near-surface winds should have resulted in a reduction in near-surface ocean circulation. One check on this deduction is the delineation of biogenic sediments associated with an equatorial current system of the early Eocene Pacific. A latitudinal seismic reflection transect across the tropical Pacific along early Paleogene ocean crust reveals a basal high-amplitude reflection package that we take to be the lower Eocene section. This unit varies in thickness by a factor of about two, with the thickest portion forming a low mound some 3˚–4˚ north of the 56 Ma …

Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part Ii—Prestack Depth Migration And Field Examples, John H. Bradford, D. S. Sawyer

CGISS Publications and Presentations

It is common in shallow seismic studies for the compressional-wave velocity in unconsolidated sediments to increase by a factor of four or more at the transition from dry or partial water saturation to full saturation. Under these conditions, conventional NMO velocity analysis fails and leads to large depth and layer thickness estimates if the Dix equation is assumed valid. Prestack depth migration (PSDM) is a means of improving image accuracy. A comparison of PSDM with conventional NMO processing for three field examples from differing hydrogeologic environments illustrates that PSDM can significantly improve image quality and accuracy.

Geologic And Tectonic History Of The Western Snake River Plain, Idaho And Oregon, Spencer H. Wood, Drew M. Clemens

Geosciences Faculty Publications and Presentations

The western Snake River Plain is a Neogene-aged intracontinental rift basin, about 70 km wide and 300 km long, trending northwest across the southern Idaho batholith. Its southeastern end merges with the northeast-trending eastern plain, a structural downwarp associated with extension along the track of the Yellowstone hot spot. Orientation of the western plain rift is parallel to several regional northwest-trending crustal discontinuities, such as the Olympic-Wallowa lineament and the Brothers fault zone, suggesting that the rift failed along zones of lithospheric weakness, as the lithosphere was softened by the passing hot spot. Crustal refraction data and gravity show that …

Identification Of Subsonic P-Waves, Paul Michaels

CGISS Publications and Presentations

A field trial was conducted to test the existence of subsonic (V_p <331 m>/s) P-waves previously reported in the literature. A 1-m-long reverse profile was acquired with three-component (3C) geophones on a sandy silt (unified classification ML). The silt had a porosity of 54%, a degree of water saturation of 63%, and a plasticity index of 10. No subsonic P-waves were observed, although high frequency (up to 1200 Hz) Rayleigh waves were identified by hodogram analysis. These surface waves were observed with horizontal velocities that varied from 40 to 200 m/s. Hodogram observations and theory suggest that …

Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part I—The Failure Of Nmo Velocity Analysis And Quantitative Error Prediction, John H. Bradford

CGISS Publications and Presentations

As seismic reflection data become more prevalent as input for quantitative environmental and engineering studies, there is a growing need to assess and improve the accuracy of reflection processing methodologies. It is common for compressional-wave velocities to increase by a factor of four or more where shallow, unconsolidated sediments change from a dry or partially watersaturated regime to full saturation. While this degree of velocity contrast is rare in conventional seismology, it is a common scenario in shallow environments and leads to significant problems when trying to record and interpret reflections within about the first 30 m below the water …

Use Of Engineering Geophysics To Investigate A Site For A Bridge Foundation, Paul Michaels

CGISS Publications and Presentations

The Idaho Transportation Department (ITD) commissioned a geophysical study to aid in the design of a replacement for an existing concrete span bridge. Because the river current was too swift to place geophones in the river, the solution was to shoot p-wave profiles in a reciprocal geometry (phones on land, shots in the river). In addition to the refraction work, a down-hole seismic profile was acquired to calibrate the surface data. Geotechnical boreholes drilled on the north and south river banks detected a laterally varying soil profile. The south-bank hole encountered 9.1 m of granular overburden, followed by 8.5 m …

Use Of Principal Component Analysis To Determine Down-Hole Tool Orientation And Enhance Sh-Waves, Paul Michaels

CGISS Publications and Presentations

A common problem in down-hole shear wave surveys is the determination of the tool rotation relative to the seismic source polarization direction. This paper reports an algorithm which has been developed to solve for this angle in the horizontal plane. The method employs Principal Component Analysis (PCA) to determine the angle from the large motion of the SH-wave (not first motion). Once the angle is known, the horizontal component data may be rotated so that one component is aligned with the source polarization, and the other orthogonal to it.

Significant findings include the following. First, subtraction of oppositely polarized source …

Use Of Engineering Geophysics In The Design Of Highway Passing Lanes, P. Michaels

CGISS Publications and Presentations

The addition of passing lanes has been a long standing need on Idaho Route 55. This narrow, winding road is one of the few routes that links Boise, Idaho, with destinations to the north. The roadway is bounded by a steep rising slope on the east, and a precipitous drop to the Payette River on the west. Additionally, the area is known for landslide hazards. Given these hazards and uncertainties in the subsurface geology, Idaho Transportation Department (ITD) commissioned an engineering geophysical survey to aid in the design of the passing lanes just south of Banks, Idaho.

The engineering design …

Boise Hydrogeophysical Research Site (Bhrs): Objectives, Design, Initial Geostatistical Results, Warren Barrash, Tom Clemo, Michael D. Knoll

CGISS Publications and Presentations

The Boise Hydrogeophysical Research Site (BHRS) is a wellfield developed in a shallow, coarse (cobble-and-sand), alluvial aquifer with the goal of developing cost-effective methods for quantitatively characterizing the distribution of permeability in heterogeneous aquifers using hydrologic and geophysical techniques. Responses to surface geophysical techniques (e.g., seismic, radar, transient electromagnetics) will be calibrated against a highly characterized control volume (the wellfield) with 3-D distributions of geologic, hydrologic, and geophysical properties determined from extensive field measurements. Also, these data sets will be used to investigate relationships between properties and to test petrophysical models. Well coring and construction methods, and the well arrangement …

Geophysical Surveys Across The Boise Hydrogeophysical Research Site To Determine Geophysical Parameters Of A Shallow, Alluvial Aquifer, William P. Clement, Michael D. Knoll, Lee M. Liberty, Paul R. Donaldson, Paul Michaels, Warren Barrash, John R. Pelton

CGISS Publications and Presentations

At the Boise Hydrogeophysical Research Site (BHRS), we are characterizing the hydrogeophysical parameters of a cobble-and-sand, unconfined aquifer using a wide variety of geophysical methods. Our goal is to develop methods for mapping variations in permeability by combining non-invasive geophysical data with hydrologic measurements. We are using seismic, ground penetrating radar, and electrical methods in a variety of configurations to provide images of and parameter distributions at the BHRS. Issues such as resolution, depth of penetration, and the ability to image the desired parameters will help determine the most effective methods. Supporting data sets from the BHRS include core analyses …

3‐D Gpr Imaging Of Complex Fluvial Stratigraphy At The Boise Hydrogeophysical Research Site, William R. Peretti, Michael D. Knoll, William P. Clement, Warren Barrash

CGISS Publications and Presentations

A series of three-dimensional (3-D) ground-penetrating radar (GPR) data sets were acquired over the central wellfield area at the Boise Hydrogeophysical Research Site (BHRS). The survey region is 30 m x 18 m and encompasses 13 wells. The goal of the surveys is to image the complex fluvial (cobble-and-sand) stratigraphy around the wellfield. These images will be used to construct 3-D models of the sedimentary architecture and to help constrain fine-scale models of hydrologic and geophysical parameters at the site. The data sets were acquired using 25 MHz, 50 MHz, 100 MHz and 200 MHz antennas. Depth of penetration ranges …

Seismic Reflection Imaging Of A Geothermal Aquifer In An Urban Setting, Lee Liberty

CGISS Publications and Presentations

A seismic reflection survey that was conducted in downtown Boise, Idaho, to help city planners site a new well for injection of spent geothermal water illustrates some methods to safely and successfully employ a seismic reflection survey in an urban setting. The objective of the seismic survey was to estimate the depth and continuity of a basalt and rhyolite volcanic sequence. Well siting was based on geothermal aquifer depth, location of interpreted faults, projected thermal impact of injection on existing wells, surface pipe extension costs, and public land availability. Seismic acquisition tests and careful processing were used to ensure high-quality …

The Effects Of Sparging On P- And Sh- Vertical Seismic Profiles, P. Michaels, W. Barrash

CGISS Publications and Presentations

While the introduction of pressurized air into an unconsolidated, coarse-grained fluvial aquifer might well be expected to affect the P-wave velocity profile below the water table, we have found that S-waves are also sensitive to changes induced by air sparging. In a study spanning over a year of sparging, observations of both P- and S-waves were conducted by Vertical Seismic Profiling (VSP). While the primary objective was to characterize the aquifer, we have found that air sparging has significantly affected both P- and S-wave propagation. Below the water table we have observed as much as a 54% decrease in P-wave …

The Anomalous Behavior Of Sh‐Waves Across The Water Table, P. Michaels, W. Barrash

CGISS Publications and Presentations

Most theoretical studies of seismic wave propagation in a porous medium do not predict a significant increase in SH-wave velocity with increasing water saturation. Although that type of behavior is commonly predicted for P-waves (and confirmed by countless observations), the expectation for SH-waves is a slight decrease in propagation velocity with increasing water saturations. While published measurements of SH-wave velocity in laboratory studies have been supportive of such a slight decrease in velocity, the data have been biased towards high pressures (typical of oil reservoirs at large depths of burial). On the other hand, the few published low pressure laboratory …

Snake: The Plain And Its People, E. B. Bentley, Bill Bonnichsen, John C. Freemuth, Bill Hackett, Glenn Oakley, F. Ross Peterson, Mark G. Plew, Todd Shallat, Steve Stuebner

Faculty & Staff Authored Books

Idaho's longest river curves west through desert landscapes, cutting deep through ancient formations, flowing through space and time. How have humans dealt with the desert? How have we been shaped by the land? SNAKE: The Plain and Its People explores the physical and ecological roots of Idaho civilization through science, social science, photography and art.