Applied Geophysics

Telford, W. M.; Geldart, L. P.; Sheriff, Robert E.

doi:10.1017/cbo9781139167932

Cited by 3,104 publications

(2,177 citation statements)

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“…There is a bowl-shaped, low resistivity (<50 ohm-m) unit in the wetland with a maximum thickness of about 5 m that tapers out toward the edges of the wetland area. The resistivity of this unit is typical of clay (<100 ohm-m), which corresponds well with the interbedded clays, silts, and peat logged in boreholes MW02-04 and CGW1 (Telford & Sheri↵, 1990). There appears to be a more resistive unit extending from electrode 48 at the surface down and to the west that corresponds to the layer of sand and gravel (80-120 ohm-m) seen in MW02 and GW05 (Telford & Sheri↵, 1990).…”

Section: Resultssupporting

confidence: 67%

“…The resistivity of this unit is typical of clay (<100 ohm-m), which corresponds well with the interbedded clays, silts, and peat logged in boreholes MW02-04 and CGW1 (Telford & Sheri↵, 1990). There appears to be a more resistive unit extending from electrode 48 at the surface down and to the west that corresponds to the layer of sand and gravel (80-120 ohm-m) seen in MW02 and GW05 (Telford & Sheri↵, 1990). Below the sand layer, resistivity increases to about 700 ohm-m, typical of the granite bedrock observed in the bottom of MW02, though this depth is near the resolution limit of this study.…”

Section: Resultssupporting

confidence: 67%

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Non-invasive flow path characterization in a mining-impacted wetland

Bethune

Randell

Runkel

et al. 2015

Journal of Contaminant Hydrology

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Time-lapse electrical resistivity (ER) is used in this study to capture the annual pulse of acid mine drainage (AMD) contamination, the so-called 'first-flush' driven by spring snowmelt, through the subsurface of a wetland downgradient of the abandoned Pennsylvania Mine workings in Central Colorado. Data were collected from mid-July to late October of 2013, with an additional dataset collected in June of 2014. ER provides a distributed measurement of changes in subsurface electrical properties at high spatial resolution. Inversion of the data shows the development through time of multiple resistive anomalies in the subsurface, which corroborating data suggest are driven by changes in total dissolved solids (TDS) localized in preferential flow pathways. Because of the non-uniqueness inherent to deterministic inversion, the exact geometry and magnitude of the anomalies is unknown, but sensitivity analyses on synthetic data taken to mimic the site suggest that the anomalies would need to be at least several meters in diameter to be adequately resolved by the inversions. Preferential flow path existence would have a critical impact on the extent of attenuation mechanisms at the site, and their further characterization could be used to parameterize reactive transport models in developing quantitative predictions of remediation strategies.iii

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Section: Resultssupporting

confidence: 67%

Section: Resultssupporting

confidence: 67%

Non-invasive flow path characterization in a mining-impacted wetland

Bethune

Randell

Runkel

et al. 2015

Journal of Contaminant Hydrology

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“…In this paper, we selected three models to represent possible geological configurations. Table 1 summarises the possible permittivity, conductivity, and permeability ranges of these geological formation [2][3]. In Table 2, we identify a "spread" factor that quantifies the wideness of each physical parameter for each layer around the average.…”

Section: The Forward Modelmentioning

confidence: 99%

Multiparameter Optimization for Electromagnetic Inversion Problem

Elkattan¹,

Kamel²

2017

AEM

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Electromagnetic (EM) methods have been extensively used in geophysical investigations such as mineral and hydrocarbon exploration as well as in geological mapping and structural studies. In this paper, we developed an inversion methodology for Electromagnetic data to determine physical parameters of a set of horizontal layers. We conducted Forward model using transmission line method. In the inversion part, we solved multi parameter optimization problem where, the parameters are conductivity, dielectric constant, and permeability of each layer. The optimization problem was solved by simulated annealing approach. The inversion methodology was tested using a set of models representing common geological formations.

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“…In honor of Galilei, the unit of gravity field is called Gal=0.01 m/s 2 . However, because of small variations of gravity fields caused by local masses and the sensitivity of gravimeters used in the field measurements, mGal=10 -3 Gal is adopted as unit of gravity field (Telford et al, 1990). In order to interpret short wavelength gravity anomalies caused by local masses with positive or negative density contrasts, a key step should be carried out to separate regional field from the anomaly caused by the target source prior to analysis of measured gravity field.…”

Section: Regional Gravity Field and Gravity Correctionsmentioning

confidence: 99%

“…Readers are referred to text books e.g. Telford et al (1990) and Blakely (1995) for details about gravity data corrections.…”

Section: Regional Gravity Field and Gravity Correctionsmentioning

confidence: 99%