Seismic instruments: article

Assessment of the effect of temperature difference on gravimetric measurements when changing the observation point
M.N. Drobyshev1
D.V. Abramov1
V.N. Koneshov1
D.A. Malysheva2
1 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia 2 Vladimir State University named after Alexander and Nikolay Stoletov, Vladimir, Russia
Journal: Seismic instruments
Tome: 58
Number: 2
Year: 2022
Pages: 75-84
UDK: 550.831.23:550.312
DOI: 10.21455/si2022.2-4
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Keywords: high-precision gravimetric observations, relative gravimeter, transient processes, sensor drift, temperature
Аnnotation: Transient processes in gravimetric data for more than 12 years are considered. During this time, more than 15 trips were made from the fundamental gravimetric point “Ledovo” to the first class point “Zapolskoe” and back using two automated relative gravimeters CG 5 Autograv. The most significant parameters that affect the readings of the instruments were identified, they turned out to be the ambient temperature, the values of the zero drift of the sensitive element of the gravimeter, and the direct increment of gravity. The zero drift was taken into account using a second-order polynomial prediction, and the remaining two parameters were described by a logarithmic dependence. The natural logarithm equation allows us to describe functions by measuring the coefficient before the logarithm (logarithmic) and additional (linear). The value of the logarithmic coefficients characterizing the duration of transient processes has a linear dependence on temperature, which means that it can characterize the measurement time at the point in the case of a significant temperature change. The magnitude of the linear coefficients characterizing the increase in gravity depends linearly on temperature when the instruments are moved to a colder environment. When the instruments are moved to a warmer environment (10 or more degrees), the dependence becomes more complex, possibly random, which also requires an increase in the measurement time at the point. The usual duration of measurements at gravimetric stations is 10 minutes. The relevance of taking temperature into account at measurement points depends on the required accuracy, for example, with a temperature difference of 10 C, the RMS of gravimetric measurements was ±0.025 mGal.