scholarly journals Seismic and Geodetic Observations of Accelerated Sliding at Haupapa/Tasman Glacier, New Zealand

2021 ◽  
Author(s):  
◽  
Samuel Taylor-Offord
Keyword(s):  
Seismic Event ◽  
Rain Rate ◽  
Water Pressure ◽  
Strain Rates ◽  
Temporal Relationships ◽  
Two Factors ◽  
Seismic Event Detection ◽  
Extensional Strain ◽  
Glacial Processes ◽  
Glacier Velocity

<p>Rain-induced accelerations of Haupapa/Tasman Glacier are accompanied by abundant seismicity. This seismicity reveals some of the glacial processes occurring at times of accelerated glacier sliding and those related directly to surficial water inputs.To study the processes occurring during rain-induced accelerations a network of seismic and geodetic sensors was deployed on the lower Haupapa/Tasman Glacier for four months in 2016. Seven categories of seismicity were defined during the study period. Glacier source processes were inferred for these categories based on their waveform characteristics, and each source was then compared to meteoric and geodetic data to discern spatial and temporal relationships. Of the seven categories of seismicity only the seismic events associated with crevasse opening were found to correlate with rain rate. Increased crevassing rate likely results from two factors: 1) increased extensional strain rates following the propagation of a subglacial cavitation front during transient accelerations and 2) hydrofracture due to the accumulation of rain in crevasses. Strain-driven crevassing is associated only with glacier acceleration, but crevasse opening via hydrofracture is inferred to occur independently of strain changes such that it is an active process at any point following heavy rainfall. Basal seismicity was not observed to respond to changes in glacier velocity or inferred subglacial water pressure, although this may be due to limitations in the seismic event detection technique.</p>

scholarly journals Seismic and Geodetic Observations of Accelerated Sliding at Haupapa/Tasman Glacier, New Zealand

2021 ◽  
Author(s):  
◽  
Samuel Taylor-Offord
Keyword(s):  
Seismic Event ◽  
Rain Rate ◽  
Water Pressure ◽  
Strain Rates ◽  
Temporal Relationships ◽  
Two Factors ◽  
Seismic Event Detection ◽  
Extensional Strain ◽  
Glacial Processes ◽  
Glacier Velocity

<p>Rain-induced accelerations of Haupapa/Tasman Glacier are accompanied by abundant seismicity. This seismicity reveals some of the glacial processes occurring at times of accelerated glacier sliding and those related directly to surficial water inputs.To study the processes occurring during rain-induced accelerations a network of seismic and geodetic sensors was deployed on the lower Haupapa/Tasman Glacier for four months in 2016. Seven categories of seismicity were defined during the study period. Glacier source processes were inferred for these categories based on their waveform characteristics, and each source was then compared to meteoric and geodetic data to discern spatial and temporal relationships. Of the seven categories of seismicity only the seismic events associated with crevasse opening were found to correlate with rain rate. Increased crevassing rate likely results from two factors: 1) increased extensional strain rates following the propagation of a subglacial cavitation front during transient accelerations and 2) hydrofracture due to the accumulation of rain in crevasses. Strain-driven crevassing is associated only with glacier acceleration, but crevasse opening via hydrofracture is inferred to occur independently of strain changes such that it is an active process at any point following heavy rainfall. Basal seismicity was not observed to respond to changes in glacier velocity or inferred subglacial water pressure, although this may be due to limitations in the seismic event detection technique.</p>

Influence of trisilanol isooctyl POSS content on the structure, morphology and rheological properties of thermoplastic polyurethane (TPU)

2020 ◽  
Vol 40 (9) ◽  
pp. 727-735
Author(s):  
Rudinei Fiorio ◽  
Chaitanya Danda ◽  
João Maia
Keyword(s):  
Thermal Stability ◽  
Rheological Properties ◽  
Thermoplastic Polyurethane ◽  
Reactive Extrusion ◽  
Strain Rates ◽  
Force Microscopy ◽  
Atomic Force ◽  
Extensional Strain ◽  
Oligomeric Silsesquioxane ◽  
Thermal Stability Of

AbstractIn this study, thermoplastic polyurethanes (TPUs) containing trisilanol isooctyl polyhedral oligomeric silsesquioxane (POSS), a reactive nanofiller, were synthesized and characterized rheologically and morphologically, and the effects of POSS content on the melt thermal stability of the TPUs are investigated. Samples containing 0, 0.23, 0.57, 1.14, and 2.23% (w/w) POSS were synthesized by reactive extrusion and characterized by Fourier transform infrared spectroscopy (FTIR), oscillatory and extensional rheometry, atomic force microscopy (AFM), and small- and wide-angle X-ray scattering (SAXS and WAXS, respectively). The rheological properties of molten TPU are time-dependent and the melt thermal stability of the TPU is maximal at 1.14% of POSS. The addition of 0.23 and 0.57% POSS promotes strain-hardening at low extensional strain rates (0.01 and 0.10 s−1), not affecting the extensional characteristics at higher strain rates. The addition of increasing amounts of POSS leads to the formation of POSS-rich clusters well dispersed in the TPU matrix. SAXS and WAXS results show that the POSS domains are amorphous and that POSS does not modify the crystalline structure of TPU. Therefore, this work indicates that synthesizing TPU in the presence of trisilanol isooctyl POSS can increase the melt thermal stability of the polymer, facilitating its processing.

Artificial neural network-based seismic detector

1995 ◽  
Vol 85 (1) ◽  
pp. 308-319 ◽  
Author(s):  
Jin Wang ◽  
Ta-Liang Teng
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Input Data ◽  
Seismic Event ◽  
Signal To Noise Ratio ◽  
Type B ◽  
Earthquake Detection ◽  
Seismic Event Detection ◽  
Artificial Neural ◽  
Better Than

Abstract An artificial neural network-based pattern classification system is applied to seismic event detection. We have designed two types of Artificial Neural Detector (AND) for real-time earthquake detection. Type A artificial neural detector (AND-A) uses the recursive STA/LTA time series as input data, and type B (AND-B) uses moving window spectrograms as input data to detect earthquake signals. The two AND's are trained under supervised learning by using a set of seismic recordings, and then the trained AND's are applied to another set of recordings for testing. Results show that the accuracy of the artificial neural network-based seismic detectors is better than that of the conventional algorithms solely based on the STA/LTA threshold. This is especially true for signals with either low signal-to-noise ratio or spikelike noises.

Physical environment of drumlin formation

1995 ◽  
Vol 41 (137) ◽  
pp. 30-38 ◽  
Author(s):  
Carrie J. Patterson ◽  
Roger LeB. Hooke
Keyword(s):  
Pore Water ◽  
Physical Environment ◽  
Large Scale ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Transverse Strain ◽  
Strain Rates

AbstractReview of published descriptions of drumlin fields suggests that the following conditions are important to drumlin growth: (1) compressive longitudinal and possibly extending transverse strain rates in the ice, (2) thin ice such as occurs near the glacier margin, and (3) high pore-water pressure in the subglacial sediments. Most drumlin fields display all of these, and no fields of well-developed drumlins were found that did not. On the oilier hand, the lithology of drumlin-forming sediment appears not to be important in promoting drumlin growth, since it varied widely, nor are the lithology and large-scale topography of the bed.

scholarly journals Depth- and time-dependent vertical strain rates at Siple Dome, Antarctica

2004 ◽  
Vol 50 (171) ◽  
pp. 511-521 ◽  
Author(s):  
Daniel H. Elsberg ◽  
William D. Harrison ◽  
Mark A. Zumberge ◽  
John L. Morack ◽  
Erin C. Pettit ◽  
...  
Keyword(s):  
Strain Rate ◽  
Time Dependence ◽  
Strain Gauge ◽  
Water Pressure ◽  
Time Dependent ◽  
Strain Rates ◽  
Ice Streams ◽  
Vertical Strain ◽  
Siple Dome ◽  
A Site

AbstractAs part of a project to investigate the flow of ice at low effective stress, two independent strain-gauge systems were used to measure vertical strain rate as a function of depth and time at Siple Dome, Antarctica. The measurements were made from January 1998 until January 2002 at the ice divide and a site 7km to the northeast on the flank. The strain-rate profiles place constraints on the rheology of ice at low stress, show the expected differences between divide and flank flow (with some structure due to firn compaction and probably ice stratigraphy), and suggest that the flow of the ice sheet has not changed much in the last 8.6 kyr. The strain rates show an unexpected time dependence on scales ranging from several months to hours, including discrete summer events at the divide. Time dependence in strain rate, water pressure, seismicity, velocity and possibly basal motion has been seen previously on the Siple Coast ice streams, but it is especially surprising on Siple Dome because the bed is cold.

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