Unconformity surface architecture of the northeast Thelon Basin, Nunavut, derived from integration of magnetic source depth estimates

2014 ◽  
Vol 2 (4) ◽  
pp. SJ117-SJ132 ◽  
Author(s):  
Victoria Tschirhart ◽  
William A. Morris ◽  
Charles W. Jefferson
Keyword(s):  
High Resolution ◽  
Seismic Refraction ◽  
Depth Estimation ◽  
Uranium Deposits ◽  
Aeromagnetic Data ◽  
Source Depth ◽  
Depth Estimate ◽  
Thelon Basin ◽  
Individual Source ◽  
Unconformity Surface

Exploration for unconformity-associated uranium deposits requires detailed 3D knowledge of the depth and morphology of the unconformity surface. Modifications of the unconformity surface by reactivated intersecting faults and favorable basement lithology are key parameters when attempting to vector toward potential deposits. In the absence of seismic reflection and closely spaced drill data, high-resolution aeromagnetic data can provide surprisingly detailed 3D constraints through the use of source depth routines. Such routines are applied to the northeastern part of the Thelon Basin, termed the Aberdeen Subbasin, in Nunavut. This region is considered prospective for unconformity-associated uranium deposits. Deposits have so far been discovered adjacent to the subbasin where they are hosted by structurally complex Neoarchean and early Paleoproterozoic supracrustal rocks. We determined the morphology of two unconformity surfaces by combining the outputs from multiple analyses of high-resolution aeromagnetic data: three semiautomated depth estimation routines (Werner deconvolution, Euler deconvolution, and source parameter imaging) and two potential field inversion procedures. Confidence in depth estimates was increased by combining the output of individual source depth algorithms. Results were integrated with previously mapped fault displacements, seismic refraction profiles, boreholes, and outcrop geology around the subbasin perimeter. An integrated pseudo-3D source depth estimate of the unconformity surface is presented as twenty-three north–south profiles. The revised model of the upper unconformity surface, the base of the Thelon Formation, shows a complex set of stepped blocks bounded by four major intersecting fault arrays with approximate offsets ranging from tens to hundreds of meters.

scholarly journals CNN Based Monocular Depth Estimation

2021 ◽  
Vol 309 ◽  
pp. 01070
Author(s):  
K. Swaraja ◽  
K. Naga Siva Pavan ◽  
S. Suryakanth Reddy ◽  
K. Ajay ◽  
P. Uday Kiran Reddy ◽  
...  
Keyword(s):  
High Resolution ◽  
Depth Map ◽  
Depth Estimation ◽  
Learning Approaches ◽  
Depth Estimate ◽  
High Performing ◽  
Depth Measurement ◽  
Ill Posed ◽  
Monocular Depth ◽  
Public Datasets

In several applications, such as scene interpretation and reconstruction, precise depth measurement from images is a significant challenge. Current depth estimate techniques frequently provide fuzzy, low-resolution estimates. With the use of transfer learning, this research executes a convolutional neural network for generating a high-resolution depth map from a single RGB image. With a typical encoder-decoder architecture, when initializing the encoder, we use features extracted from high-performing pre-trained networks, as well as augmentation and training procedures that lead to more accurate outcomes. We demonstrate how, even with a very basic decoder, our approach can provide complete high-resolution depth maps. A wide number of deep learning approaches have recently been presented, and they have showed significant promise in dealing with the classical ill-posed issue. The studies are carried out using KITTI and NYU Depth v2, two widely utilized public datasets. We also examine the errors created by various models in order to expose the shortcomings of present approaches which accomplishes viable performance on KITTI besides NYU Depth v2.

scholarly journals Geophysical investigations for stability and safety mitigation of regional crude-oil pipeline near abandoned coal mines

2021 ◽  
Vol 18 (1) ◽  
pp. 145-162
Author(s):  
B Butchibabu ◽  
Prosanta Kumar Khan ◽  
P C Jha
Keyword(s):  
High Resolution ◽  
Crude Oil ◽  
Seismic Refraction ◽  
High Resolution Imaging ◽  
Weak Zone ◽  
Near Surface ◽  
Oil Pipeline ◽  
Refraction Tomography ◽  
Geophysical Investigations ◽  
Resolution Imaging

Abstract This study aims for the protection of a crude-oil pipeline, buried at a shallow depth, against a probable environmental hazard and pilferage. Both surface and borehole geophysical techniques such as electrical resistivity tomography (ERT), ground penetrating radar (GPR), surface seismic refraction tomography (SRT), cross-hole seismic tomography (CST) and cross-hole seismic profiling (CSP) were used to map the vulnerable zones. Data were acquired using ERT, GPR and SRT along the pipeline for a length of 750 m, and across the pipeline for a length of 4096 m (over 16 profiles of ERT and SRT with a separation of 50 m) for high-resolution imaging of the near-surface features. Borehole techniques, based on six CSP and three CST, were carried out at potentially vulnerable locations up to a depth of 30 m to complement the surface mapping with high-resolution imaging of deeper features. The ERT results revealed the presence of voids or cavities below the pipeline. A major weak zone was identified at the central part of the study area extending significantly deep into the subsurface. CSP and CST results also confirmed the presence of weak zones below the pipeline. The integrated geophysical investigations helped to detect the old workings and a deformation zone in the overburden. These features near the pipeline produced instability leading to deformation in the overburden, and led to subsidence in close vicinity of the concerned area. The area for imminent subsidence, proposed based on the results of the present comprehensive geophysical investigations, was found critical for the pipeline.

Source depth estimation using multi-station waveform data

1984 ◽  
Vol 74 (5) ◽  
pp. 1623-1643
Author(s):  
Falguni Roy
Keyword(s):  
Depth Estimation ◽  
The United States ◽  
Digital Data ◽  
United States Geological Survey ◽  
Travel Times ◽  
Source Depth ◽  
Time Data ◽  
Waveform Data ◽  
Level Ii ◽  
Level I

Abstract A depth estimation procedure has been described which essentially attempts to identify depth phases by analyzing multi-station waveform data (hereafter called level II data) in various ways including deconvolution, prediction error filtering, and spectral analysis of the signals. In the absence of such observable phases, other methods based on S-P, ScS-P, and SKS-P travel times are tried to get an estimate of the source depth. The procedure was applied to waveform data collected from 31 globally distributed stations for the period between 1 and 15 October 1980. The digital data were analyzed at the temporary data center facilities of the National Defense Research Institute, Stockholm, Sweden. During this period, a total number of 162 events in the magnitude range 3.5 to 6.2 were defined by analyzing first arrival time data (hereafter called level I data) alone. For 120 of these events, it was possible to estimate depths using the present procedure. The applicability of the procedure was found to be 100 per cent for the events with mb > 4.8 and 88 per cent for the events with mb > 4. A comparison of level I depths and level II depths (the depths as obtained from level I and level II data, respectively) with that of the United States Geological Survey estimates indicated that it will be necessary to have at least one local station (Δ < 10°) among the level I data to obtain reasonable depth estimates from such data alone. Further, it has been shown that S wave travel times could be successfully utilized for the estimation of source depth.

Effects of near-surface waveguides on shallow high-resolution seismic refraction and reflection data

1996 ◽  
Vol 23 (5) ◽  
pp. 495-498 ◽  
Author(s):  
J. O. A. Robertsson ◽  
K. Holliger ◽  
A. G. Green ◽  
A. Pugin ◽  
R. De Iaco
Keyword(s):  
High Resolution ◽  
Seismic Refraction ◽  
Near Surface ◽  
Reflection Data

scholarly journals Analytic Signal Depth from High Resolution Aeromagnetic Data over the Gongola Basin Upper Benue Trough Northeastern Nigeria

2021 ◽  
Vol 25 (4) ◽  
pp. 585-590
Author(s):  
H. Musa ◽  
N.E. Bassey ◽  
R. Bello
Keyword(s):  
High Resolution ◽  
Magnetic Structure ◽  
Horizontal Cylinder ◽  
Analytic Signal ◽  
Aeromagnetic Data ◽  
Polynomial Fitting ◽  
Benue Trough ◽  
Local Maxima ◽  
Depth Determination ◽  
Programming Software

The study of high-resolution aeromagnetic data was carried out over the Gongola basin, upper Benue trough, northeastern Nigeria, for analytic signal depth determination. Total intensity magnetic map obtained from the data using the Oasis Montaj TM programming software was used to get the residual map by polynomial fitting, from where the analytic signal was obtained with the use of anomaly width at half the amplitude (X1/2). This was used to carry out depth estimations over the study area. The results showed that it peaks over the magnetic structure with local maxima over its edges (boundaries or contact), and the amplitude is simply related to magnetization, likewise results also showed that the depth estimates were in the range of 1.2 to 5.9 km and were calculated for contact, dyke/sill and horizontal cylinder respectively. The lowest values are from DD profiles, while the highs are from AA profiles. This work is important in identifying dykes, contacts and intrusives over an area.

Petrology and geochronology of Paleoproterozoic intrusive rocks, Kiggavik uranium camp, Nunavut

2015 ◽  
Vol 52 (7) ◽  
pp. 495-518 ◽  
Author(s):  
J.M.J. Scott ◽  
T.D. Peterson ◽  
W.J. Davis ◽  
C.W. Jefferson ◽  
B.L. Cousens
Keyword(s):  
Granitic Rocks ◽  
Uranium Deposits ◽  
Zircon Age ◽  
Core Samples ◽  
Thelon Basin ◽  
Intrusive Rocks ◽  
Uranium Exploration ◽  
Melt Infiltration ◽  
Granitic Intrusions ◽  
Baker Lake

We investigated the age and petrology of Paleoproterozoic granitic intrusions in the area of the Kiggavik uranium exploration camp, near the southeast margin of the Aberdeen subbasin of the Thelon Basin. A subset of these intrusions (e.g., the Lone Gull stock) is spatially associated with and mineralized by basement hosted, unconformity-related uranium deposits. Surface (outcrop) samples have field relations, textures, and compositions consistent with Hudson Suite granitoids and mixtures of monzogranite with minette. We obtained U–Pb (zircon) ages ranging from ca. 1818 to 1840 Ma, within the known range of the Hudson Suite and cogenetic minettes of the Baker Lake Group (1.80–1.84 Ga). Core samples of granitic rocks adjacent to mineralized zones are more complex and indicate an influence from the younger Nueltin Granite (Kivalliq Igneous Suite, ca. 1.77–1.73 Ga). One sample from the Lone Gull stock contains two zircon populations in texturally distinctive domains, one at 1806 ± 41 Ma and the other at 1748 ± 9.4 Ma. A porphyritic hypabyssal syenite below the Bong deposit yielded a U–Pb zircon age of 1837.8 ± 7.7 Ma and a U–Pb titanite age of 1758.5 ± 44 Ma. We recognize a Kivalliq-age overprint in the form of metasomatism and partial remelting or melt infiltration in the drill core samples, which is not evident at the surface and is consistent with the presence of a Nueltin Granite intrusive complex at depth. The geochemistry and primary igneous textures of the Bong syenite, including its euhedral zircons, resemble those of lava flows near the base of the Baker Lake Group, and we recognize a mixed magma (i.e., Martell Syenite) continuum between intrusive Hudson granitoids and minette with extrusive equivalents in the lower felsic minette member of the Christopher Island Formation.

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