scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

Abstract Deformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

AbstractDeformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

Across-strike variations of fault slip-rates constrained using in-situ cosmogenic 36Cl concentrations.

2020 ◽  
Author(s):  
Francesco Iezzi ◽  
Gerald Roberts ◽  
Joanna Faure Walker ◽  
Ioannis Papanikolaou ◽  
Athanassios Ganas ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Strain Rate ◽  
Active Faults ◽  
Slip Rate ◽  
High Temporal Resolution ◽  
Strain Rates ◽  
Time Intervals ◽  
The Holocene ◽  
Regional Strain

<p>It is important to constrain the spatial distribution of strain-rate in deforming continental material because this underpins calculations of continental rheology and seismic hazard. To do so, it is becoming increasingly common to use combinations of GPS and historical and instrumental seismicity data to constrain regional strain-rate fields. However, GPS geodetic sites, whether permanent or campaign stations, tend to be widely-spaced relative to the spacing of active faults with known Holocene offsets. At the same time, the interpretation of seismicity data can be difficult due to lack of historical seismicity in cases where local fault recurrence intervals are longer than the historical record. This causes uncertainty on how regional strain-rates are partitioned in time and space, and hence with uncertainty regarding calculations of continental rheology and seismic hazard. To overcome this issue, we have gained high temporal resolution slip-rate histories for three parallel faults using in situ <sup>36</sup>Cl cosmogenic dating of the exposure of three parallel normal fault planes that have been progressively exhumed by earthquakes. We study the region around Athens, central Greece, where there also exists a relatively-dense GPS network and extensive records of instrumental and historical earthquakes. This allows to compare regional, decadal strain-rates measured with GPS geodesy with strain-rates across the faults implied by slip since ~40,000 years BP. We show that faults have all had episodic behaviour during the Holocene, with alternating earthquake clusters and periods of quiescence through time. Despite the fact that all three faults have been active in the Holocene, each fault slips in discrete time intervals lasting a few millennia, so that only one fault accommodates strain at any time. We show that magnitudes of strain-rates during the high slip-rate episodes are comparable with the regional strain-rates measured with GPS (fault strain-rates are 50-100% of the value of GPS regional strain-rate). Thus, if the GPS-derived strain-rate applies over longer time intervals, it appears that single faults dominate the strain-accumulation at any given time, with crustal deformation and seismic hazard localised within a distributed network of faults.</p><p> </p>

scholarly journals Erratum: The role of in situ stress in determining hydraulic connectivity in a fractured rock aquifer (Australia)

2011 ◽  
Vol 19 (7) ◽  
pp. 1453-1453
Author(s):  
Luke Mortimer ◽  
Adnan Aydin ◽  
Craig T. Simmons ◽  
Graham Heinson ◽  
Andrew J. Love
Keyword(s):  
Fractured Rock ◽  
In Situ Stress ◽  
Fractured Rock Aquifer

Dynamic Recrystallization Behaviour in Cu-Sn-P Alloy for High Strength Copper Tube

2010 ◽  
Vol 654-656 ◽  
pp. 1271-1274 ◽  
Author(s):  
Masato Watanabe ◽  
Takashi Shirai ◽  
Akihiko Ishibashi ◽  
Hiromi Miura
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Heat Exchangers ◽  
High Strength ◽  
Strain Rates ◽  
Testing Conditions ◽  
Lower Temperature ◽  
Increasing Temperature ◽  
Different Content

Dynamic recrystallization (DRX) behaviour in a newly developed Cu-Sn-P alloy for heat exchangers and tubes was systematically investigated. For this purpose, Cu-Sn-P alloys with different content of Sn were deformed in compression at temperatures between 1073 K and 1213 K and at various strain rates from 2 x 10-4 s-1 to 2 x 10-1 s-1. The onset of DRX was more advanced with increasing temperature and with decreasing strain rate. Full DRX was not achieved at the testing conditions of lower temperature and higher strain rate even after straining to ε = 1.0. This tendency was more significant in the alloy with higher Sn content. With increasing Sn content, the flow stress and the obtained grains size became higher and finer, respectively. These experimental results indicate the important role of Sn for strengthening and microstructual control.

Texture Evolution of Magnesium Single Crystals Deformed by High-Pressure Torsion

2008 ◽  
Vol 584-586 ◽  
pp. 263-268 ◽  
Author(s):  
Bartlomiej J. Bonarski ◽  
Erhard Schafler ◽  
Borys Mikułowski ◽  
Michael Zehetbauer
Keyword(s):  
High Pressure ◽  
Single Crystals ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Texture Evolution ◽  
In Situ Stress ◽  
Higher Symmetry ◽  
Strain Measurements ◽  
X Ray

Single crystals of technical purity Magnesium (99.8 wt.%) of initial orientations [ ] 2 1 10 and [ ] 2 2 11 were subjected to HPT deformation at room temperature up to strains of 10. The microstructural evolution has been analyzed by X-ray microtexture investigations and by in-situ stress-strain measurements. The results can be described in terms of shear arising from HPT deformation and - with higher strains - in terms of recrystallization. In crystals with hard orientation[ ] 2 2 11 , these features occur at smaller strains than in crystals with soft orientation [ ] 2 1 10 , i.e. with higher symmetry. In general, the observed textures and strength variations are much stronger than those reported for fcc HPT deformed metals.

Low-Temperature Halo-Carbon Homoepitaxial Growth of 4H-SiC: Morphology, Doping, and Role of HCl Additive

2007 ◽  
Vol 556-557 ◽  
pp. 133-136 ◽  
Author(s):  
Huang De Lin ◽  
Galyna Melnychuk ◽  
Jeffery L. Wyatt ◽  
Yaroslav Koshka
Keyword(s):  
Low Temperature ◽  
Nitrogen Concentration ◽  
Aluminum Concentration ◽  
Silicon Cluster ◽  
Vapor Species ◽  
Aluminum Doping ◽  
Homoepitaxial Growth ◽  
Order Of Magnitude

Low-temperature epitaxial growth of 4H-SiC with CH3Cl carbon precursor was further developed. In-situ doping with nitrogen and aluminum was investigated. The nitrogen concentration in epitaxial layers grown on the C face was almost two orders of magnitude higher than that in the Si-face epilayers grown in the same growth run at 13000C. The opposite trend was observed for intentional aluminum doping, with more than an order of magnitude higher aluminum concentration incorporated in Si-face epilayers. High values of nitrogen and aluminum doping well in excess of 1020 cm-3 without any obvious epilayer morphology degradation can be achieved on C-face and Siface respectively. Addition of HCl during halo-carbon growth at 13000C resulted in drastic improvement of the surface morphology. Also, a significant increase of the growth rate took place confirming that the improvement in the epilayer morphology during HCl-assisted growth is predominantly related to silicon cluster etching by additional Cl-containing vapor species.

scholarly journals Stacking of InAs/InP(001) quantum wires studied by in situ stress measurements: Role of inhomogeneous stress fields

2004 ◽  
Vol 84 (23) ◽  
pp. 4723-4725 ◽  
Author(s):  
David Fuster ◽  
Marı́a Ujué González ◽  
Luisa González ◽  
Yolanda González ◽  
Teresa Ben ◽  
...  
Keyword(s):  
Quantum Wires ◽  
In Situ Stress ◽  
Stress Fields ◽  
Stress Measurements ◽  
In Situ Stress Measurements
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