Estimation of horizontal deformation rates based on tachymetric measurements
Processing measurements collected yearly in the geothermal area Bjarnarflag in North-East Iceland from 2015 to 2018
Veronica Tollenaar (TU Delft - Civil Engineering & Geosciences)
Freek van Leijen – Mentor (TU Delft - Mathematical Geodesy and Positioning)
S. Verhagen – Mentor (TU Delft - Mathematical Geodesy and Positioning)
Ihor Smal – Mentor (TU Delft - Optical and Laser Remote Sensing)
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Abstract
Measurements of a tachymetric network in the geothermal area of Bjarnarflag in North-East Iceland are performed during four consecutive years (2015-2018). For the yearly adjustment of the measurements an alternative iteration scheme to Baarda’s ’B-method of testing’ is proposed, because the level of significance of the F-test performed in the detection step is too large due to the large redundancy of the measurements. The proposed alternative method detects outliers and verifies the stochastic model simultaneously, resulting in 3
to 4% rejected measurements per year. From the yearly solutions absolute and relative horizontal velocities are estimated. The relative velocities are significant, but have large uncertainties. Adding three years of data reduces the mean standard deviation of the estimated velocities from 2.4 mm in east-direction to 0.9 mm and 1.8 mm in north-direction to 0.8 mm. The improvement of precision can be accelerated by reevaluating the stochastic input parameters, adding more GNSS measurements and reconsidering the network design.
Improved horizontal relative velocities can be used to understand the horizontal deformation patterns in the area of study due to extraction of water or steam by the geothermal powerplant, due to the instability of the benchmaks or due to natural processes.