THE USE OF GROUND-PENETRATING RADAR FOR CHARACTERIZING SEDIMENTS UNDER TRANSIENT FLOW CONDITIONS

2004 ◽  
pp. 107-127 ◽  
Author(s):  
MICHAEL B. KOWALSKY ◽  
YORAM RUBIN ◽  
PETER DIETRICH
Keyword(s):  
Ground Penetrating Radar ◽  
Transient Flow ◽  
Flow Conditions ◽  
Ground Penetrating

scholarly journals Wet subglacial bedforms of the NE Greenland Ice Stream shear margins

2019 ◽  
Vol 60 (80) ◽  
pp. 91-99 ◽  
Author(s):  
Kiya L. Riverman ◽  
Sridhar Anandakrishnan ◽  
Richard B. Alley ◽  
Nicholas Holschuh ◽  
Christine F. Dow ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Acoustic Impedance ◽  
Impedance Analysis ◽  
Flow Conditions ◽  
Lateral Shear ◽  
Ice Flow ◽  
Ice Stream ◽  
Water Saturated ◽  
Ground Penetrating

AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

scholarly journals Modelling of Kealey Ice Rise, Antarctica, reveals stable ice-flow conditions in East Ellsworth Land over millennia

2014 ◽  
Vol 60 (219) ◽  
pp. 139-146 ◽  
Author(s):  
Carlos Martín ◽  
G. Hilmar Gudmundsson ◽  
Edward C. King
Keyword(s):  
Ground Penetrating Radar ◽  
Stationary Flow ◽  
Radar Data ◽  
Flow Conditions ◽  
West Antarctica ◽  
Land Area ◽  
Ice Flow ◽  
Local Conditions ◽  
Flow Solver ◽  
Ground Penetrating

AbstractFlow at ice divides, their shape, size and internal structure depend not only on local conditions, but also on the flow regimes and past histories of the surrounding ice masses. Here we use field data from Kealey Ice Rise, Ellsworth Land, West Antarctica, in combination with flow modelling to investigate any possible signs of transients in the flow of the surrounding ice masses. Kealey Ice Rise shows linear surface features running parallel to its ridge in satellite imagery and a conspicuous layering in the ground-penetrating radar data known as double-peaked Raymond bumps. Through numerical modelling, by using an anisotropic full-Stokes thermomechanical flow solver, we analyse the evolution of Kealey Ice Rise and the timescales involved. We conclude that the features observed in the stratigraphy of Kealey Ice Rise require at least 3 ka of near-stationary flow conditions. However, we cannot exclude the possibility of a recent flow reorganization in the last century. We stress that the signs of stationary flow in radar stratigraphy observed in Kealey Ice Rise have been observed in other ice divides in the East Ellsworth Land area, suggesting stationary flow conditions over a millennial timescale in the region.

scholarly journals Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland

2017 ◽  
Vol 48 (6) ◽  
pp. 1666-1681 ◽  
Author(s):  
Verity Flett ◽  
Louise Maurice ◽  
Andrew Finlayson ◽  
Andrew R. Black ◽  
Alan M. MacDonald ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Tracer Tests ◽  
Tracer Test ◽  
Low Flow ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Tracer Testing ◽  
Flow Through ◽  
Conduit System ◽  
Ground Penetrating

Abstract Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s−1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s−1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s−1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers.

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

Deteksi Bentuk Objek Bawah Tanah Menggunakan Pengolahan Citra B-Scan pada Ground Penetrating Radar (GPR)

2017 ◽  
Vol 3 (1) ◽  
pp. 73-83
Author(s):  
Rahmayati Alindra ◽  
Heroe Wijanto ◽  
Koredianto Usman
Keyword(s):  
Signal Processing ◽  
Ground Penetrating Radar ◽  
Post Processing ◽  
Data Survey ◽  
Ground Penetrating

Ground Penetrating Radar (GPR) adalah salah satu jenis radar yang digunakan untuk menyelidiki kondisi di bawah permukaan tanah tanpa harus menggali dan merusak tanah. Sistem GPR terdiri atas pengirim (transmitter), yaitu antena yang terhubung ke generator sinyal dan bagian penerima (receiver), yaitu antena yang terhubung ke LNA dan ADC yang kemudian terhubung ke unit pengolahan data hasil survey serta display sebagai tampilan output-nya dan post  processing untuk alat bantu mendapatkan informasi mengenai suatu objek. GPR bekerja dengan cara memancarkan gelombang elektromagnetik ke dalam tanah dan menerima sinyal yang dipantulkan oleh objek-objek di bawah permukaan tanah. Sinyal yang diterima kemudian diolah pada bagian signal processing dengan tujuan untuk menghasilkan gambaran kondisi di bawah permukaan tanah yang dapat dengan mudah dibaca dan diinterpretasikan oleh user. Signal processing sendiri terdiri dari beberapa tahap yaitu A-Scan yang meliputi perbaikan sinyal dan pendektesian objek satu dimensi, B-Scan untuk pemrosesan data dua dimensi  dan C-Scan untuk pemrosesan data tiga dimensi. Metode yang digunakan pada pemrosesan B-Scan salah satunya adalah dengan  teknik pemrosesan citra. Dengan pemrosesan citra, data survey B-scan diolah untuk didapatkan informasi mengenai objek. Pada penelitian ini, diterapkan teori gradien garis pada pemrosesan citra B-scan untuk menentukan bentuk dua dimensi dari objek bawah tanah yaitu persegi, segitiga atau lingkaran. 

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