Several debris-covered glaciers occupy tributaries of upper Beacon Valley, Antarctica. Understanding their flow dynamics and ice thickness is important for palaeoclimate studies and for understanding the origins of ancient ice elsewhere in the McMurdo Dry Valleys region. We present the results of several shallow seismic surveys in Mullins Valley, where the largest of these debris-covered glaciers is located. Our results suggest that beneath a thin sublimation till and near-surface horizon of dirty glacier ice, lies relatively pure glacier ice (P-wave velocity ~3700–3800 m s-1), with total thickness estimates of ~90–95 m towards the valley head, and ~40–65 m near the entrance to Beacon Valley, ~2.5 km downglacier. P-wave velocities decrease downvalley, suggesting that the material properties of the ice change with increasing distance from the ice-accumulation zone. These new data are used to calibrate an ice thickness profile for the active portion of the Mullins Valley debris-covered glacier (upper ~3.5 km) and to shed light on the origin and spatial distribution of enclosed debris.

http://www.planetary.brown.edu/pdfs/3243.pdf

Shallow seismic surveys and ice thickness estimates of the Mullins Valley debris-covered glacier, McMurdo Dry Valleys, Antarctica

http://www.geol.lsu.edu/jlorenzo/literature/Juan/ENG_GEO_Lorenzoetal.2014.pdf

Integrated seismic and cone penetration test observations at a distressed earthen levee: Marrero, Louisiana, U.S.A.

http://www.geol.lsu.edu/jlorenzo/literature/Juan/CAGEO_2012_sandtank_offprint.pdf

Benchmark hydrogeophysical data from a physical seismic model

https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=4713&context=gradschool_dissertations

Effects of stress and water saturation on seismic velocity and attenuation in near surface sediments

Seismic investigation in the near-surface is complicated by highly attenuating media, large interparticle stresses, and variable water saturation, so new tools and methodology are necessary to understand the relationships between velocity, attenuation, and physical properties of the propagating media. A new shear wave source is developed for investigation of gas-charged, organic-rich sediments because compressional waves are highly attenuated and currently available sources are inadequate. The new source compares favorably to a traditional hammer impact source, producing a signal with a broader-band of frequencies (30-100Hz cf. 30-60Hz) and signal-to-noise ratios (SNR) equivalent to ~3 stacked hammer blows to the hammer impact source. Ideal source signals must be broadband in frequency, have a high SNR, be consistent, and have precise start times; all traits of the new shear source. A new constitutive model predicting seismic velocity is developed because current models do not include interparticle stresses which are especially important in materials with large cohesive and capillary pressures such as clays. The new proposed methodology calculates elastic moduli of granular matrices in near-surface environments by incorporating an updated definition of total effective stress into Hertz-Mindlin theory and calculates the elastic moduli of granular materials by extending Biot-Gassmann theory to include pressure effects induced by water saturation. As water saturation increases in shallow sediments, theoretically calculated seismic velocities decrease in clay and increase in sand because of the respective interparticle stresses in these media. The proposed model calculates seismic velocities that compare well with measured field velocities from the literature. A field-transferrable lab experiment shows the simultaneous dependence of quality factor (Q) on water saturation and stress in unconsolidated sand. Local Q values (Qint) increase the most with depth (dQ/dz=43 m-1) and stress (dQ/dS=0.0025/Pa) in dry sand and the least in partially saturated sand (dQ/dz=10m-1 and dQ/dS=0.0013/Pa) where attenuation created by local fluid flow reaches a maximum. Expectations for Qint values with depth can be extrapolated from dQ/dS and are bounded by Qint of the dry (QD) and partially saturated (QPS) media (e.g.,QD>Qint>QPS). Qint deviations outside this range can be explained by a divergence in effective stress, attenuation mechanism, or lithology. 

Two Approaches to Noise Tests

A modeling study of a subsalt exploration problem was used to help understand imaging issues and to help plan solutions to those issues. By comparing images from various acquisition geometries ranging from wide (WATS) to narrow (NATS) one can say WATS and certain XWATS geometries should resolve most of the subsalt imaging problems for the area of interest. Despite these improvements subsalt illumination remains an issue for all types of acquisition geometries as demonstrated by interpreting images and creating amplitude maps. WATS geometries seem to be more robust when faced with velocity model inaccuracies.

Modeling Case Study of a Subsalt Exploration Concept

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Two Approaches to Noise Tests

Modeling Case Study of a Subsalt Exploration Concept