Sensitivity of seismic refraction inversion to smooth and blocky velocity gradients

Nielson, Travis; Bradford, John H.

doi:10.1190/segam2015-5931741.1

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…The initial models for the inversion were derived by taking a Delta t-V for each receiver location and averaging the velocities at common depths, creating a pseudo-2D Delta t-V inversion (Jansen, 2010). WET inversion with the pseudo-2D Delta t-V initial model has proven to be an effective inversion schema at resolving large scale near-surface velocity features (Zelt et al, 2013) and for the estimation of smooth critical zone velocity structures (Nielson and Bradford, 2015). The inversions were carried out for 150 iterations, long enough for the RMS error to reduce to <3% of the maximum travel time of the modeled traces for all the inversion.…”

Section: Methodsmentioning

confidence: 99%

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

et al. 2021

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In the northern hemisphere within snow-dominated mountainous watersheds north-facing slopes are commonly more deeply weathered than south-facing slopes. This has been attributed to a more persistent snowpack on the north facing aspects. A persistent snowpack releases its water into the subsurface in a single large pulse, which propagates the water deeper into the subsurface than the series of small pulses characteristic of the intermittent snowpack on south-facing slopes. Johnston Draw is an east-draining catchment in the Reynolds Creek Critical Zone Observatory, Idaho that spans a 300 m elevation gradient. The north-facing slope hosts a persistent snowpack that increases in volume up drainage, while the south-facing slope has intermittent snowpack throughout the drainage. We hypothesize that the largest difference in weathering depth between the two aspects will occur where the difference in snow accumulation between the aspects is also greatest. To test this hypothesis, we conducted four seismic refraction tomography surveys within Johnston Draw from inlet to outlet and perpendicular to drainage direction. From these measurements, we calculate the weathering zone thickness from the P-wave velocity profiles. We conclude that the maximum difference in weathering between aspects occurs ¾ of the way up the drainage from the outlet, where the difference in snow accumulation is highest. Above and below this point, the subsurface is more equally weathered and the snow accumulations are more similar. We also observed that the thickness of the weathering zone increased with decreasing elevation and interpret this to be related to the observed increase soil moisture at lower elevations. Our observations support the hypothesis that deeper snow accumulation leads to deeper weathering when all other variables are held equal. One caveat is the possibility that the denser vegetation contributes to deeper weathering on north-facing slopes via soil retention or higher rates of biological weathering.

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Section: Methodsmentioning

confidence: 99%

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

et al. 2021

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“…The initial models for the inversion were derived by taking a Delta t-V for each receiver location and averaging the velocities at common depths, creating a pseudo-2D Delta t-V inversion [Jansen, 2010]. WET inversion with the pseudo-2D Delta t-V initial model has proven to be an effective inversion schema at resolving large scale near-surface velocity features [Zelt et al, 2013] and for the estimation of smooth critical zone velocity structures [Nielson and Bradford, 2015]. The inversions were carried out for 150 iterations,long enough for the RMS error to reduce to less than 3% of the maximum travel time of the modeled traces for all the inversion.…”

Section: Figurementioning

confidence: 99%

Application of Hydrogeophysical Imaging in the Reynolds Creek Critical Zone Observatory

Nielson¹

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Holbrook, at the University of Wyoming, and his student Brady Flinchum for being so generous with their data, insight, and time, with their help my understanding of the critical zone was greatly advanced. The countless professors and students in the BSU Geosciences department, who were all so generous with their insights into the hydrologic and geomorphic implications of this work. Mark Seyfried and Steve Van Vactor at the USDA ARS for providing the hydrologic data that made this work come together. The at least two dozen volunteer graduate and undergraduate students who were deceived into participating in grueling field campaigns in the middle of a hot summer. Of my fellows students Aida Mendieta, Diego Domenzain, Amy Streimke, and Paden Gould, were brave enough to participate in multiple surveys and thus invaluable in the field. And lastly the Reynolds Creek Critical Zone Observatory for funding me and this research.

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Sensitivity of seismic refraction inversion to smooth and blocky velocity gradients

Cited by 2 publications

References 5 publications

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

Application of Hydrogeophysical Imaging in the Reynolds Creek Critical Zone Observatory

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