The Use of Strainmeters to Study Oscillation Processes in a Wide Frequency Range
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Use of Strainmeters to Study Oscillation Processes in a Wide Frequency Range V. Yu. Timofeeva, *, D. G. Ardyukova, A. V. Timofeeva, E. V. Boykoa, V. M. Semibalamutb, Y. N. Fominb, S. V. Panovc, and M. D. Parushkinc aTrofimuk
Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia b Federal Research Center Geophysical Survey, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia cInstitute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] Abstract—Adit-based linear strain measurements made with strainmeters 1 to 100 m long allow oscillation processes to be studied in a wide range: from a few tens of hertz to several years. Both seismic waves from earthquakes and long-period oscillatory signals are recorded, related to tectonic processes. The paper describes measurements made with rod and laser strain metering systems in an adit of the Talaya seismic station (coordinates 51.68° N, 103.65° E, Lake Baikal Region). The elastic moduli of rocks were evaluated using strainmeter, microbarograph data, and petrophysical core analysis. The Earth’s integral rheological parameters, through the Earth’s free and tidal oscillations, are calculated. Our findings are in good agreement with modern models of the Earth’s internal structure. The paper describes coseismic and long-term volumetric strain variations induced by large regional earthquakes. Keywords: rod strainmeter, laser strainmeter, Baikal region, seiches in Lake Baikal, Earth’s free and tidal oscillations, earthquakes, volumetric strain variations DOI: 10.3103/S0747923920040106
INTRODUCTION Strainmeters have been used in studying crustal deformations since the 1900s. Rod (quartz/invar) strainmeters with a baseline of up to 50 m, allow the detection of deformations on the order of 10–7–10–10 (Benioff, 1935; Latynina and Karmaleeva, 1978; Melchior, 1966). Open- and closed-type strainmeters have been created, with the advent of lasers; in the latter case, the laser beam travels toward a reflector in a vacuum pipe. Closed-type systems up to 800 m long, can detect signals from earthquakes and nuclear explosions as well as tidal variations provided that the land topography is flat (Beaumont and Berger, 1974). Strain measurement techniques are used to solve different problems of geology and geophysics at various spatial and temporal scales: the investigation of seismic wave propagation (Chupin, 2019), the noise of various origins, free oscillations of the Earth (Jahr et al., 2006), the structure of our planet, the free oscillations of the solid and liquid cores of the Earth, and tidal effects; the research into modern tectonic deformations and seismicity; and the assessment of anthropogenic impacts on the geological environment. In seismically active regions, strainmeters are widely used, with a prospect of earthquake prediction (Guseva, 1986; Agnew, 1986; Timofeev et al., 2020).
Under certain conditions, deformation on the
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