Improving corrections in microgravimetric surveys through modelling of ocean loading effects

1998 ◽  
Author(s):  
M. Llubes ◽  
J. Hinderer ◽  
M. Amalvict ◽  
M. F. Lalancette-Le Quentrec
Keyword(s):  
Loading Effects ◽  
Ocean Loading

A Discussion on the measurement and interpretation of changes of strain in the Earth - An improved servo-controlled tiltmeter system and latest measurements in Sweden

1973 ◽  
Vol 274 (1239) ◽  
pp. 305-309 ◽  
Keyword(s):  
Pressure Effects ◽  
Land Uplift ◽  
Bearing Plate ◽  
Tidal Forces ◽  
Mercury Column ◽  
First Results ◽  
Loading Effects ◽  
Ocean Loading ◽  
Servo Signal ◽  
Horizontal Pendulum

Two serious shortcomings in horizontal pendulums used for tilt measurements are nonlinearity in their response to tilt and sensitivities which vary with time. These difficulties may be eliminated if a horizontal pendulum is used as a null indicator. A description is given of a horizontal pendulum apparatus which automatically compensates for ground tilt. The pendulum apparatus is designed so that it may be tilted by varying the pressure in an expansible bearing plate made of stainless steel which is placed at its base. Pressure changes are produced in the bearing plate by varying the height of a column of mercury, a process which can be previously calibrated with great precision. The position of the pendulum beam is sensed by an electro-optical transducer which provides a suitable servo signal to adjust the height of the mercury column when the instrument undergoes tilting. The servo signal can be recorded directly on an ink chart recorder or digitally. First results have been obtained in a test station. It is planned to establish an array of geodynamic stations in Scandinavia incorporating these tiltmeters alongside recording gravity meters in order to study crustal movements by tidal forces, atmospheric pressure effects, ocean loading effects and possibly the process of land uplift in Fennoscandia.

scholarly journals Non-tidal ocean loading effects on geodetic GPS heights

2011 ◽  
Vol 38 (9) ◽  
pp. n/a-n/a ◽  
Author(s):  
S. D. P. Williams ◽  
N. T. Penna
Keyword(s):  
Loading Effects ◽  
Ocean Loading

Use of a vibrating beam MEMS accelerometer for surface microgravimetry

2021 ◽  
Author(s):  
Adrian Topham ◽  
Milind Pandit ◽  
Zhijun Du ◽  
Guillermo Sobreviela ◽  
Douglas Young ◽  
...  
Keyword(s):  
Ground Motion ◽  
Dynamic Range ◽  
Digital Signal ◽  
Statistical Correlation ◽  
Earth Tides ◽  
Integration Time ◽  
Mems Accelerometer ◽  
Loading Effects ◽  
Ocean Loading ◽  
Teleseismic Events

<p>A vibrating beam MEMS gravimeter with an Allan deviation of 9 μGal for a 1000 s integration time, a noise floor of 10 μGal/√Hz, and measurement over the full ±1 g dynamic range (1 g = 9.81 ms<sup>−2</sup>) is presented. In addition to a direct digital signal output, the sensor system possesses built-in tilt compensation capabilities and a 2-stage temperature control that is stable to 500 µK.</p><p>Instances of Earth tidal tracking and ground motion records corresponding to several teleseismic events are demonstrated. The output response from tracking of the Earth tides is compared to the data obtained from the software TSoft and a statistical correlation R of 0.92 is obtained between the conditioned MEMS dataset over a period of ~4 days and the predicted Earth tides model from TSoft following correction for ocean loading effects.</p><p>The device also recorded the ground motion from several teleseismic events during the testing period, a prominent event among them is the 6.2 M<sub>L</sub> earthquake near to Petrinja, Croatia, which occurred on December 29<sup>th</sup>, 2020. The MEMS sensor has demonstrated excellent performance as a long-period seismometer and the response is compared to the seismograms recorded by two nearby BGS broadband seismic stations. </p><p>Advances in microgravity sensor detection capability will be shown to match feasibility modelling for void detection. Results demonstrate that a vibrating beam MEMS accelerometer can be used for measurements requiring high levels of stability and resolution with wider implications for precision measurement. Gravimetry use to warn of imminent failures due to a range of shallow hazards include assessing damage in the built environment, transmission losses in utilities, territory breach and storage containment loss.</p>

Revisiting non-tidal ocean loading corrections for high precision terrestrial gravimetry

2021 ◽  
Author(s):  
Ezequiel D. Antokoletz ◽  
Hartmut Wziontek ◽  
Henryk Dobslaw ◽  
Claudia N. Tocho
Keyword(s):  
Time Series ◽  
High Precision ◽  
Ocean Circulation ◽  
Ocean Dynamics ◽  
Atmospheric Effects ◽  
Satellite Gravity ◽  
Simple Assumption ◽  
Superconducting Gravimeters ◽  
Loading Effects ◽  
Ocean Loading

<p>In modelling of atmospheric loading effects in terrestrial gravimetry by numerical weather models, often the Inverse Barometer (IB) hypothesis is applied over oceans. This simple assumption implies an isostatic compensation of the oceans to atmospheric pressure changes, causing no net deformation of the seafloor. However, the IB hypothesis is in general not valid for periods shorter than a few weeks and, consequently, the ocean dynamics cannot be neglected. In particular, for the correction of high precision gravity time series as e.g. obtained from superconducting gravimeters, it is essential to model even small contributions in order to separate different effects. When including non-tidal ocean loading effects from ocean circulation models into atmospheric models, special care has to be taken of the interface between the atmosphere and the oceans in order not to account contributions twice.</p><p>The established approach for modelling non-tidal ocean loading effects is revised in this study. When combining it with the modelling of atmospheric effects for terrestrial gravimetry, it is shown that Newtonian attraction contributions from the atmosphere may be accounted twice. To solve this problem, an alternative is proposed and tested which further reduces the variability of the gravity residuals, as shown for a set of four superconducting gravity meters globally distributed.</p><p>The improvement is achieved by a different treatment of the Newtonian attraction component related to the IB effect. Discrepancies up to the μGal level are demonstrated, depending on the location of the station. With several simplifications, the approach can be made operational and included in existing services, further improving the compatibility of terrestrial gravity time series with satellite gravity observations.</p>

Ocean loading effects on the prediction of Antarctic glacial isostatic uplift and gravity rates

2010 ◽  
Vol 84 (5) ◽  
pp. 305-317 ◽  
Author(s):  
Karen M. Simon ◽  
Thomas S. James ◽  
Erik R. Ivins
Keyword(s):  
Isostatic Uplift ◽  
Loading Effects ◽  
Ocean Loading

Observation of gravity fluctuations due to tide-induced groundwater table fluctuations with two superconducting gravimeters

2020 ◽  
Author(s):  
Hiroki Goto ◽  
Mituhiko Sugihara ◽  
Yuji Nishi ◽  
Hiroshi Ikeda
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Groundwater Resources ◽  
Groundwater Table ◽  
Surface Gravity ◽  
Superconducting Gravimeters ◽  
Loading Effects ◽  
Ocean Loading ◽  
Aquifer Properties ◽  
The Difference

<p>Estimation of aquifer hydraulic properties is necessary for predicting groundwater flow and hence managing groundwater resources. Analysis of tide-induced groundwater table fluctuations in unconfined aquifers is one of the methods to estimate aquifer properties. Changes in groundwater level affect surface gravity. Consequently, surface gravity in coastal regions is expected to fluctuate due to the groundwater table fluctuations and is potentially useful for estimating aquifer properties. Moreover, gravity measurements are sensitive to mass redistribution around the observation location and therefore are useful for estimating the storage coefficient of an aquifer. In this study, surface gravity and unconfined groundwater level were measured continuously near the coast of Japan to observe gravity fluctuations due to the tide-induced groundwater table fluctuations. Groundwater level measured in two wells at 60 and 90 m distances from the coastline fluctuated in response to ocean tides. Two superconducting gravimeters (SGs) were installed at 70 and 80 m distances from the coastline and at an elevation of 8 m. After taking the difference between gravity values recorded with the two SGs and then correcting the gravity difference for ocean loading effects, diurnal and semi-diurnal gravity fluctuations, which are possibly due to tide-induced groundwater table fluctuations, were recognized. These results suggest that gravity monitoring with two SGs at different distances from the coastline can be useful for observing gravity fluctuations due to tide-induced groundwater table fluctuations and possibly for estimating aquifer hydraulic properties.</p>

scholarly journals Applications of Biocatalysts for Sustainable Oxidation of Phenolic Pollutants: A Review

2021 ◽  
Vol 13 (15) ◽  
pp. 8620
Author(s):  
Sanaz Salehi ◽  
Kourosh Abdollahi ◽  
Reza Panahi ◽  
Nejat Rahmanian ◽  
Mozaffar Shakeri ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Operating Conditions ◽  
Phenolic Pollutants ◽  
Petroleum Refinery Wastewater ◽  
Start Up ◽  
Low Concentrations ◽  
Effective Removal ◽  
Wide Range ◽  
Loading Effects ◽  
Spent Caustic

Phenol and its derivatives are hazardous, teratogenic and mutagenic, and have gained significant attention in recent years due to their high toxicity even at low concentrations. Phenolic compounds appear in petroleum refinery wastewater from several sources, such as the neutralized spent caustic waste streams, the tank water drain, the desalter effluent and the production unit. Therefore, effective treatments of such wastewaters are crucial. Conventional techniques used to treat these wastewaters pose several drawbacks, such as incomplete or low efficient removal of phenols. Recently, biocatalysts have attracted much attention for the sustainable and effective removal of toxic chemicals like phenols from wastewaters. The advantages of biocatalytic processes over the conventional treatment methods are their ability to operate over a wide range of operating conditions, low consumption of oxidants, simpler process control, and no delays or shock loading effects associated with the start-up/shutdown of the plant. Among different biocatalysts, oxidoreductases (i.e., tyrosinase, laccase and horseradish peroxidase) are known as green catalysts with massive potentialities to sustainably tackle phenolic contaminants of high concerns. Such enzymes mainly catalyze the o-hydroxylation of a broad spectrum of environmentally related contaminants into their corresponding o-diphenols. This review covers the latest advancement regarding the exploitation of these enzymes for sustainable oxidation of phenolic compounds in wastewater, and suggests a way forward.

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