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

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.

Effects of Ocean Tide Load on Vertical Crustal Deformation in Northeastern Margin of Qinghai Tibet Plateau

Periodic crustal movement are mainly caused by ocean tides and changes of atmospheric pressure. In this project, the researcher has used the spherical harmonic coefficient of the ocean tide and actual observation data to study the impact on vertical crustal deformation due to changes of oceanic tide loading from 2012 to 2017 at the northeastern margin of the Qinghai-Tibet Plateau, based on the theory of crustal load deformation. The result shows that changes in oceanic tide loading have little impact on vertical crustal deformation compared with the impact of atmospheric loading at the northeastern margin of the Qinghai. The impact range of oceanic tide loading in this region is within ±3mm. In contrast, impact of atmospheric loading can reach ±12mm.

Estimation of present-day glacial isostatic adjustment, ice mass change and elastic vertical crustal deformation over the Antarctic ice sheet

ABSTRACTThis study explores an iterative method for simultaneously estimating the present-day glacial isostatic adjustment (GIA), ice mass change and elastic vertical crustal deformation of the Antarctic ice sheet (AIS) for the period October 2003–October 2009. The estimations are derived by combining mass measurements of the GRACE mission and surface height observations of the ICESat mission under the constraint of GPS vertical crustal deformation rates in the spatial domain. The influence of active subglacial lakes on GIA estimates are mitigated for the first time through additional processing of ICESat data. The inferred GIA shows that the strongest uplift is found in the Amundsen Sea Embayment (ASE) sector and subsidence mostly occurs in Adelie Terre and the East Antarctica inland. The total GIA-related mass change estimates for the entire AIS, West Antarctica Ice Sheet (WAIS), East Antarctica Ice Sheet (EAIS), and Antarctic Peninsula Ice Sheet (APIS) are 43 ± 38, 53 ± 24, −23 ± 29 and 13 ± 6 Gt a−1, respectively. The overall ice mass change of the AIS is −46 ± 43 Gt a−1 (WAIS: −104 ± 25, EAIS: 77 ± 35, APIS: −20 ± 6). The most significant ice mass loss and most significant elastic vertical crustal deformations are concentrated in the ASE and northern Antarctic Peninsula.

TO THE QUESTION OF CRUSTAL DEFORMATION FROM SEASONAL LOAD WEIGHT CHIRKEI RESERVOIR

В статье сделан анализ данных непрерывных электрометрических наблюдений в скважине, расположенной в районе правого борта плотины Чиркейской ГЭС за период времени 20102013 гг., которые коррелируют с сезонным изменением уровня воды в водохранилище. Один из механизмов связи между изменениями уровня воды в водохранилище и кажущимся сопротивлением пород может быть деформационный, т.е., сезонное изменение нагрузки, создаваемое весом водохранилища приводит к упругой деформации земной коры. Численные оценки показывают, что значение вертикальной относительной деформации земной коры в районе плотины ГЭС может достигать величин 1,2105 The article presents an analysis of data continuous electrometric observations in the borehole located in the right side of the dam of the Chirkei hydroelectric power station for the period 20102013, which correlate with seasonal changes in water level in the reservoir. One of the mechanisms of the link between changes in water level in the reservoir and the apparent resistance of rocks can be deformation, i.e., the seasonal change of the load created by the weight of the reservoir leads to elastic deformation of the earths crust. Numerical estimates show that the value of relative vertical crustal deformation in the area of the hydroelectric dam may reach values of 1,2105.