The measurement capabilities of the hydrostatic level with a base of 1-3 km are described. The paper presents physical assessments of the effects related to the influence of changes in the parameters of meteorological conditions (atmospheric pressure, temperature, and its gradients along a track). The dynamic characteristics of the instrument and its limiting resolution, determined by both its own thermal fluctuations and the influence of seismic noise, are considered. A new radiotechnical method for measuring variations if the fluid level in the measuring vessel is discussed, characterized by a simple and reliable design and a large dynamic measurement range while maintaining the high sensitivity necessary for constructing long base sys tems.
The results of the analysis of continuous precise time series of atmospheric pressure and groundwater level fluctuations in a well drilled to a depth of 400 m in the territory of Moscow are presented. The observations are remarkable in terms of their duration of more than 22 years (from February 2, 1993 to April 4, 2015) and by the sampling interval of 10 min. These long observations are suitable for exploring the stationarity of the properties of hydrogeological time series in a seismically quiet region, which is important from the methodological standpoint for interpreting the similar observations in seismically active regions aimed at earthquake prediction. Factor and cluster analysis applied to the sequence of multivariate vectors ofthe statistical properties of groundwater level time series in the successive 10-day windows after adaptive compensation for atmospheric pressure effects distinguish five different statistically significant states of the time series with the transitions between them. An attempt to geophysically interpret the revealed states is made. Two significant periods – 46 and 275 days – are established by spectral analysis of the sequence of the transitions times between the clusters.
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