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

2009 ◽  
Vol 10 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Demian M. Saffer ◽  
Alexander W. McKiernan
Keyword(s):  
Pore Water ◽  
Nankai Trough ◽  
Southwest Japan

Experimental Evaluation of Initial Characteristics of DONET Pressure Sensors

2018 ◽  
Vol 52 (3) ◽  
pp. 109-119
Author(s):  
Hiroyuki Matsumoto ◽  
Eiichiro Aaraki ◽  
Katsuyoshi Kawaguchi
Keyword(s):  
Nankai Trough ◽  
Pressure Sensors ◽  
Initial Response ◽  
Hydraulic Pressure ◽  
Network System ◽  
Southwest Japan ◽  
Operational Life ◽  
Pressure Standard ◽  
Pressure Changes

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.

scholarly journals 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

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.

The Test Study to the Changes of Excess Pore Water Pressure during Precast Pile Construction

2012 ◽  
Vol 193-194 ◽  
pp. 1010-1013
Author(s):  
Shu Qing Zhao
Keyword(s):  
Pore Water ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Soil Pressure ◽  
Excess Pore Water Pressure ◽  
Test Study ◽  
Excess Pore

The construct to precast pile in thick clayey soil can cause the accumulation of excess pore water pressure. The high excess pore pressure can make soil, buildings and pipes surrounded have large deflection, even make them injured. Combining with actual projects, this paper presents an in-situ model test on the changes of excess pore water pressure caused by precast pile construct. It is found that the radius of influence range for single pile driven is about 15m，the excess pore water pressure can reach or even exceed the above effective soil pressure, and there are two relatively stable stages.

In situ electrokinetic isolation of cadmium from paddy soil through pore water drainage: Effects of voltage gradient and soil moisture

2018 ◽  
Vol 337 ◽  
pp. 210-219 ◽  
Author(s):  
Xianqiang Tang ◽  
Qingyun Li ◽  
Zhenhua Wang ◽  
Yanping Hu ◽  
Yuan Hu ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Pore Water ◽  
Paddy Soil ◽  
Voltage Gradient ◽  
Water Drainage

scholarly journals The control of hydrogen sulfide on benthic iron and cadmium fluxes in the oxygen minimum zone off Peru

2019 ◽  
Author(s):  
Anna Plass ◽  
Christian Schlosser ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Eric P. Achterberg ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Trace Metals ◽  
Pore Water ◽  
Oxygen Minimum Zone ◽  
Benthic Fluxes ◽  
Benthic Chamber ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Sediments in oxygen-depleted marine environments can be an important sink or source of bio-essential trace metals in the ocean. However, the key mechanisms controlling the release from or burial of trace metals in sediments are not exactly understood. Here, we investigate the benthic biogeochemical cycling of Fe and Cd in the oxygen minimum zone off Peru. We combine bottom water profiles, pore water profiles, as well as benthic fluxes determined from pore water profiles and in-situ from benthic chamber incubations along a depth transect at 12° S. In agreement with previous studies, both concentration-depth profiles and in-situ benthic fluxes indicate a Fe release from sediments into bottom waters. Diffusive Fe fluxes and Fe fluxes from benthic chamber incubations are roughly consistent (0.3–17.1 mmol m−2 y−1), indicating that diffusion is the main transport mechanism of dissolved Fe across the sediment-water interface. The occurrence of mats of sulfur oxidizing bacteria on the seafloor represents an important control on the spatial distribution of Fe fluxes by regulating hydrogen sulfide (H2S) concentrations and, potentially, Fe sulfide precipitation within the surface sediment. Removal of dissolved Fe after its release to anoxic bottom waters is rapid in the first 4 m away from the seafloor (half-life

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