The contemporary strain rate field in Uruguay and surrounding region and possible implications for seismic hazard

ABSTRACTChanging rates of water input can affect both the flow of glaciers and ice sheets and their propensity to crevasse. Here we examine geodetic and seismic observations during two substantial (10–18-times background velocity) rain-induced glacier accelerations at Haupapa/Tasman Glacier, New Zealand. Changes in rain rate result in glacier acceleration and associated uplift, which propagate down-glacier. This pattern of acceleration results in a change to the strain rate field, which correlates with an order of magnitude increase in the apparent seismicity rate and an overall down-glacier migration in located seismicity. After each acceleration event the apparent seismicity rate decreases to below the pre-acceleration rate for 3 days. This suggests that seismic events associated with surface crevasse growth occur early during phases of glacier acceleration due to elevated extensional stresses, and then do not occur again until stresses recover.

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Mechanical deformation model of the western United States instantaneous strain-rate field

Geophysical Journal International ◽

10.1111/j.1365-246x.2006.03019.x ◽

2006 ◽

Vol 167 (1) ◽

pp. 421-444 ◽

Cited By ~ 6

Author(s):

Fred F. Pollitz ◽

Mathilde Vergnolle

Keyword(s):

United States ◽

Strain Rate ◽

Mechanical Deformation ◽

Western United States ◽

Deformation Model ◽

Instantaneous Strain ◽

Strain Rate Field

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

10.5194/egusphere-egu2020-756 ◽

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

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 36Cl 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.&#160;

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Numerical Investigation of Fluid Flow in a Chandler Loop

Journal of Biomechanical Engineering ◽

10.1115/1.4027330 ◽

2014 ◽

Vol 136 (7) ◽

Cited By ~ 7

Author(s):

Hisham Touma ◽

Iskender Sahin ◽

Tidimogo Gaamangwe ◽

Maud B. Gorbet ◽

Sean D. Peterson

Keyword(s):

Strain Rate ◽

Rotation Rate ◽

Tangential Velocity ◽

Working Fluid ◽

Radius Of Curvature ◽

Straight Tube ◽

Dean Number ◽

Fill Ratio ◽

Chandler Loop ◽

Strain Rate Field

The Chandler loop is an artificial circulatory platform for in vitro hemodynamic experiments. In most experiments, the working fluid is subjected to a strain rate field via rotation of the Chandler loop, which, in turn, induces biochemical responses of the suspended cells. For low rotation rates, the strain rate field can be approximated using laminar flow in a straight tube. However, as the rotation rate increases, the effect of the tube curvature causes significant deviation from the laminar straight tube approximation. In this manuscript, we investigate the flow and associated strain rate field of an incompressible Newtonian fluid in a Chandler loop as a function of the governing nondimensional parameters. Analytical estimates of the strain rate from a perturbation solution for pressure driven steady flow in a curved tube suggest that the strain rate should increase with Dean number, which is proportional to the tangential velocity of the rotating tube, and the radius to radius of curvature ratio of the loop. Parametrically varying the rotation rate, tube geometry, and fill ratio of the loop show that strain rate can actually decrease with Dean number. We show that this is due to the nonlinear relationship between the tube rotation rate and height difference between the two menisci in the rotating tube, which provides the driving pressure gradient. An alternative Dean number is presented to naturally incorporate the fill ratio and collapse the numerical data. Using this modified Dean number, we propose an empirical formula for predicting the average fluid strain rate magnitude that is valid over a much wider parameter range than the more restrictive straight tube-based prediction.

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Strain Rate Evolution in Aluminium Alloy Measured by ESPI during Tensile Test

Materials Science Forum ◽

10.4028/www.scientific.net/msf.614.155 ◽

2009 ◽

Vol 614 ◽

pp. 155-162 ◽

Cited By ~ 2

Author(s):

Johann Petit ◽

Guillaume Montay ◽

Manuel François

Keyword(s):

Tensile Test ◽

Strain Rate ◽

Aluminium Alloy ◽

Speckle Pattern ◽

Local Strain ◽

Plastic Instability ◽

Electronic Speckle Pattern Interferometry ◽

The Moment ◽

The One ◽

Strain Rate Field

The original and significant achievement of this work is to analyse strain rate field in aluminium alloy sheets during micro tensile test. In-plane Electronic Speckle Pattern Interferometry is used to follow the evolution of the local strain in real time. This paper is based on the detection of the localization on a relatively small area of the analysed specimen: less than 5mm × 4mm area. Moreover the speed of the tensile machine is very low, 0.2 to 0.1µm/s. The phase shifting technique is used to obtain the fringes representative of the material displacement. We can therefore get a very good accuracy in the material displacement. A heterogeneity in strain rate field can be noticed from a deformation stage which doesn’t coincide with the one calculated by the classic Considère’s criterion (dF=0) for the diffuse neck initiation (or plastic instability). We also show, the moment when one of the two slip bands systems becomes predominant, and even only one band continues to exist, this occurring widely before fracture. Finally, the fracture of the specimen occurs across this remaining band. The total strain is measured with a second camera, in white light, and is correlated together with the strain rate field to study the localization.

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The strain rate field in the eastern Mediterranean region, estimated by repeated GPS measurements

Tectonophysics ◽

10.1016/s0040-1951(98)00102-4 ◽

1998 ◽

Vol 294 (3-4) ◽

pp. 237-252 ◽

Cited By ~ 104

Author(s):

Hans-Gert Kahle ◽

Christian Straub ◽

Robert Reilinger ◽

Simon McClusky ◽

Robert King ◽

...

Keyword(s):

Strain Rate ◽

Mediterranean Region ◽

Eastern Mediterranean ◽

Eastern Mediterranean Region ◽

Gps Measurements ◽

Strain Rate Field

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GEODYNAMICS

GEODYNAMICS ◽

10.23939/jgd2011.01.005 ◽

2011 ◽

Vol 1(10)2011 (1(10)) ◽

pp. 5-16

Author(s):

N. Marchenko ◽

◽

K. R. Tretyak ◽

O.V. Serant ◽

R.O. Vysotenko ◽

...

Keyword(s):

Strain Rate ◽

Eastern Europe ◽

Spline Functions ◽

Gps Data ◽

Strain Rate Tensor ◽

Least Squares Collocation ◽

Velocity Tensor ◽

Element Approach ◽

Strain Rate Field ◽

Gps Observations

Estimated from GPS observations velocities of GPS-stations were used to obtain 2D-model velocities and strain rate field in the Eastern Europe. The study of the velocities field in the region was done in a few steps. The first one consists of the development of the finite element approach on the geosphere based on bicubic spline functions and least squares collocation method for the interpolation scattered GPS-data to the regular nodes. The second one represents the inversion of velocities from GPS-observations to the strain rate tensor. In order to test this approach we chose to apply it to an Eastern Europe where such problem was not solved before. This region is not extensively instrumented as yet but it is well studied by a geological and geophysical data. Test is based on derived in the Research Institute of Geodesy and Cartography (Kyiv, Ukraine) solution of GPS-observations data processing for the region. Finally the full eigenvalue/eigenvector solution for deformations velocity tensor of concerned territory is preformed and analyzed.

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