Experimental Evaluation of Initial Characteristics of DONET Pressure Sensors

AbstractThe dense ocean floor network system for detecting earthquakes and tsunamis, DONET, began its operations in the Nankai Trough, southwest Japan, in 2010. The present study focuses on the pressure sensors used in DONET observatories to measure hydraulic pressure changes. Pressure sensors specify their performance for both hysteresis and repeatability; however, no details of the sensors' stability are currently available. It is known that pressure sensors typically show a drift in their readings over their operational life span. We evaluated the initial behavior of the pressure sensors before deployment into the deep sea by using our own high accuracy pressure standard. In our experiment, 20 MPa of hydrostatic pressure is applied to the pressure sensors under a constant temperature of 2°C for a duration of 1 month. Our experiment suggests that the procedure is effective at clarifying the initial response and stability of the pressure sensors before deployment. It is proved that the repeatability of the initial response is well reproduced. Then the in situ measurements are processed and compared to the experimental measurements. The pressure sensors, to which a pressure equivalent to the deployed depth is applied, show that the sensor drift in the experiment corresponds in rate and direction to that from the in situ measurements.

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Drift Characteristics of DONET Pressure Sensors Determined From In-Situ and Experimental Measurements

Frontiers in Earth Science ◽

10.3389/feart.2020.600966 ◽

2021 ◽

Vol 8 ◽

Author(s):

Hiroyuki Matsumoto ◽

Eiichiro Araki

Keyword(s):

Crustal Deformation ◽

Deep Sea ◽

Pressure Sensors ◽

Hydraulic Pressure ◽

Megathrust Earthquakes ◽

Initial Stage ◽

Sensor Drift ◽

Pressure Standard ◽

Vertical Crustal Deformation

DONET, the dense ocean-floor network system for earthquakes and tsunamis, began operations in the Nankai Trough, SW Japan, in 2010. The present study focuses on pressure sensors that are being used as tsunami meters to measure changes in hydraulic pressure. Pressure sensors typically show a drift in their readings over their operational lifespan. DONET pressure sensors can act as geodetic sensors measuring vertical crustal deformation change over time if the sensor drift can be accurately corrected. Monitoring crustal deformation before the occurrence of megathrust earthquakes is performed by discriminating between the vertical crustal deformation and the sensor drift of the pressure sensors. Therefore, in this study, we evaluated the sensor drift shown by the DONET pressure sensors since their deployment into the deep-sea, by removing the tidal component and confirming the occurrence of sensor drift. We evaluated the initial behavior of pressure sensors before deep-sea deployment using our own high-accuracy pressure standard. Our experiment involved 20-MPa pressurization for the pressure sensors under an ambient temperature of 2°C for a duration of 1 month. Some sensor drifts in our experiment correspond in rate and direction to those from the in-situ measurements determined to be in the initial stage. Our experiment suggests that the pre-deployment pressurization of pressure sensors can be an effective procedure to determine the sensor drift after sensor deployment into the deep-sea.

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Evaluation of in situ smectite dehydration as a pore water freshening mechanism in the Nankai Trough, offshore southwest Japan

Geochemistry Geophysics Geosystems ◽

10.1029/2008gc002226 ◽

2009 ◽

Vol 10 (2) ◽

pp. n/a-n/a ◽

Cited By ~ 35

Author(s):

Demian M. Saffer ◽

Alexander W. McKiernan

Keyword(s):

Pore Water ◽

Nankai Trough ◽

Southwest Japan

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Diagnosis of in Situ Air Sparging Performance Using Groundwater Pressure Changes During Startup and Shutdown

10.21236/ada406092 ◽

2001 ◽

Author(s):

Richard L. Johnson ◽

Paul C. Johnson ◽

Tim L. Johnson ◽

Neil Thomas ◽

Andrea Leason

Keyword(s):

Air Sparging ◽

Pressure Changes

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Driving stress and seismotectonic implications of the 2013 Mw5.8 Awaji Island earthquake, southwestern Japan, based on earthquake focal mechanisms before and after the mainshock

Earth Planets and Space ◽

10.1186/s40623-020-01292-1 ◽

2020 ◽

Vol 72 (1) ◽

Author(s):

Kazutoshi Imanishi ◽

Makiko Ohtani ◽

Takahiko Uchide

Keyword(s):

Stress Field ◽

Stress Tensor ◽

Nankai Trough ◽

Source Region ◽

Local Scale ◽

Southwest Japan ◽

Stress Tensor Inversion ◽

Earthquake Fault ◽

Reverse Faulting ◽

Before And After

Abstract A driving stress of the Mw5.8 reverse-faulting Awaji Island earthquake (2013), southwest Japan, was investigated using focal mechanism solutions of earthquakes before and after the mainshock. The seismic records from regional high-sensitivity seismic stations were used. Further, the stress tensor inversion method was applied to infer the stress fields in the source region. The results of the stress tensor inversion and the slip tendency analysis revealed that the stress field within the source region deviates from the surrounding area, in which the stress field locally contains a reverse-faulting component with ENE–WSW compression. This local fluctuation in the stress field is key to producing reverse-faulting earthquakes. The existing knowledge on regional-scale stress (tens to hundreds of km) cannot predict the occurrence of the Awaji Island earthquake, emphasizing the importance of estimating local-scale (< tens of km) stress information. It is possible that the local-scale stress heterogeneity has been formed by local tectonic movement, i.e., the formation of flexures in combination with recurring deep aseismic slips. The coseismic Coulomb stress change, induced by the disastrous 1995 Mw6.9 Kobe earthquake, increased along the fault plane of the Awaji Island earthquake; however, the postseismic stress change was negative. We concluded that the gradual stress build-up, due to the interseismic plate locking along the Nankai trough, overcame the postseismic stress reduction in a few years, pushing the Awaji Island earthquake fault over its failure threshold in 2013. The observation that the earthquake occurred in response to the interseismic plate locking has an important implication in terms of seismotectonics in southwest Japan, facilitating further research on the causal relationship between the inland earthquake activity and the Nankai trough earthquake. Furthermore, this study highlighted that the dataset before the mainshock may not have sufficient information to reflect the stress field in the source region due to the lack of earthquakes in that region. This is because the earthquake fault is generally locked prior to the mainshock. Further research is needed for estimating the stress field in the vicinity of an earthquake fault via seismicity before the mainshock alone.

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Abrupt glacier motion and reorganization of basal shear stress following the establishment of a connected drainage system

Journal of Glaciology ◽

10.3189/172756501781831972 ◽

2001 ◽

Vol 47 (158) ◽

pp. 472-480 ◽

Cited By ~ 61

Author(s):

Jeffrey L. Kavanaugh ◽

Garry K. C. Clarke

Keyword(s):

Pressure Sensors ◽

Drainage System ◽

Yukon Territory ◽

Stable Configuration ◽

Drainage Patterns ◽

Pressure Pulses ◽

Gradual Failure ◽

Basal Shear ◽

Pressure Changes ◽

Glacier Motion

AbstractThree episodes of strong basal motion occurred at Trapridge Glacier, Yukon Territory, Canada, on 11 June 1995 following the establishment of a connected subglacial drainage system. Responses to these “spring events” are noted in the records for 42 instruments and were recorded throughout the ∼60 000 m2 study area. Strong basal motion during the events is indicated by ploughmeter, load-bolt and vertical-strain records, and abrupt pressure changes in several transducer records denote damage caused by extreme pressure pulses. These pressure pulses, generated by the abrupt basal motion, also resulted in the failure of seven pressure sensors. Records for pressure, turbidity and conductivity sensors indicate that basal drainage patterns did not change significantly during the events. Geophone records suggest that the episodes of basal motion were precipitated by the gradual failure of a “sticky spot” following hydraulic connection of part of the study area. This failure resulted in the transfer of basal stress to the unconnected region of the bed during the course of the events. No evidence for strong basal motion is seen in the instrument records for several weeks following the events, suggesting that the mechanical adjustments resulted in a stable configuration of basal stresses. This event illustrates how unstable situations can be quickly accommodated by mechanical adjustments at the glacier bed.

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Interplate coupling along the Nankai Trough off southwest Japan derived from GPS measurements

Geophysical Research Letters ◽

10.1029/1999gl900145 ◽

1999 ◽

Vol 26 (7) ◽

pp. 927-930 ◽

Cited By ~ 26

Author(s):

Taku Ozawa ◽

Takao Tabei ◽

Shin-ichi Miyazaki

Keyword(s):

Nankai Trough ◽

Southwest Japan ◽

Gps Measurements ◽

Interplate Coupling

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Tunable In Situ 3D-Printed PVDF-TrFE Piezoelectric Arrays

Sensors ◽

10.3390/s21155032 ◽

2021 ◽

Vol 21 (15) ◽

pp. 5032

Author(s):

Alec Ikei ◽

James Wissman ◽

Kaushik Sampath ◽

Gregory Yesner ◽

Syed N. Qadri

Keyword(s):

3D Printing ◽

Polyvinylidene Fluoride ◽

Vinylidene Fluoride ◽

Mechanical Strain ◽

Pressure Sensors ◽

Strain Ratio ◽

Ex Situ ◽

Order Of Magnitude ◽

3D Printed

In the functional 3D-printing field, poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) has been shown to be a more promising choice of material over polyvinylidene fluoride (PVDF), due to its ability to be poled to a high level of piezoelectric performance without a large mechanical strain ratio. In this work, a novel presentation of in situ 3D printing and poling of PVDF-TrFE is shown with a d33 performance of up to 18 pC N−1, more than an order of magnitude larger than previously reported in situ poled polymer piezoelectrics. This finding paves the way forward for pressure sensors with much higher sensitivity and accuracy. In addition, the ability of in situ pole sensors to demonstrate different performance levels is shown in a fully 3D-printed five-element sensor array, accelerating and increasing the design space for complex sensing arrays. The in situ poled sample performance was compared to the performance of samples prepared through an ex situ corona poling process.

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Characteristics of bottom pressure sensors of the dense ocean-floor network system for earthquakes and tsunamis

Journal of Japan Society of Civil Engineers Ser B2 (Coastal Engineering) ◽

10.2208/kaigan.67.i_286 ◽

2011 ◽

Vol 67 (2) ◽

pp. I_286-I_290 ◽

Cited By ~ 1

Author(s):

Hiroyuki MATSUMOTO ◽

Eiichiro ARAKI ◽

Katsuyoshi KAWAGUCHI ◽

Yoshiyuki KANEDA

Keyword(s):

Pressure Sensors ◽

Ocean Floor ◽

Network System ◽

Bottom Pressure

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Isolating In-Situ Grip and Push Force Distribution from Hand-Handle Contact Pressure with an Industrial Electric Nutrunner

Sensors ◽

10.3390/s21238120 ◽

2021 ◽

Vol 21 (23) ◽

pp. 8120

Author(s):

Cederick Landry ◽

Daniel Loewen ◽

Harish Rao ◽

Brendan L. Pinto ◽

Robert Bahensky ◽

...

Keyword(s):

Grip Force ◽

Pressure Sensors ◽

Measurement Instrument ◽

Force Distribution ◽

Pressure Measurements ◽

Industrial Workers ◽

Shoulder Injuries ◽

Significant Difference ◽

Measured Pressure

Objectives: Grip force during hand tool operation is the primary contributor to tendon strain and related wrist injuries, whereas push force is a contributor to shoulder injuries. However, both cannot be directly measured using a single measurement instrument. The objective of this research was to develop and test an algorithm to isolate the grip and push force distributions from in-situ hand-handle pressure measurements and to quantify their distributions among industrial workers using an electric nutrunner. Methods: Experienced automobile assembly line workers used an industrial nutrunner to tighten fasteners at various locations and postures. The pressure applied by the hand on the tool handle was measured dynamically using pressure sensors mounted on the handle. An algorithm was developed to compute the push force applied to the handle of an electric pistol-grip nutrunner based on recorded pressure measurements. An optimization problem was solved to find the contribution of each measured pressure to the actual pushing force of the tool. Finally, the grip force was determined from the difference between the measured pressure and the calculated pushing pressure. Results: The grip force and push force were successfully isolated and there was no correlation between the two forces. The computed grip force increased from low to high fastener locations, whereas the push force significantly increased during overhead fastening. A significant difference across the participants’ computed grip forces was observed. The grip force distribution showed that its contribution to total hand force was larger than other definitions in the literature. Conclusions: The developed algorithm can aid in better understanding the risk of injury associated with different tasks through the notion of grip and push force distribution. This was shown to be important as even workers with considerable power tool experience applied significantly more grip and push force than other participants, all of whom successfully completed each task. Moreover, the fact that both forces were uncorrelated shows the need for extracting them independently.

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