Computation of gravity station is necessary to correct for all the factors that are not due to the density contrast in the subsurface. The earth model is a function of several effects such as the latitude correction, the free air correction and finally the Bouguer correction. And the observed gravity is a function of the conversion factor for specific meter, drift correction adn tidal correction.
figure 1 work flow field gravity data reduction
Drift Correction
A phenomenon known as drift occurs in every gravimeter. Drift is defined as the change in the elasticity of the springs over time and is different for every gravimeter. Correction to the observed gravity readings for instrument drift requires one to occupy a base station several times during the day of the survey. It is important to take readings periodically because of the erratic nature of drift.The meter reading is plotted against time and it is assumed that drift is linear between re-occupations. The drift correction is then substracted for each station.
Tidal Correction
Latitude Correction
Free Air Correction
Bouguer Correction
Preliminary processing to convert observed values into gravity value carried out at the base camp to allow rapid quality control (QC) of the field data. Figure 1 shows a work flow for field gravity data reduction and figure 2 shows a result of field gravity data reduction. Table 1 shown an example of calculation of observed gravity value.
table 1 Example of calculation of observed gravity value
figure 2 A work flow for the final gravity reduction
picture 1 inversion result of top carbonate at xx island
picture 2 3D model vs 2D model slicing
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