Detection and Evaluation of the Slichter Mode Based on Long-Term Strain Observations

To search for the Slichter mode (1S1), the longest mode of Earth’s free oscillations, long-term (more than 15 years) strain data of the Baksan laser interferometer–strainmeter (with a measuring-arm length of 75 m) of Sternberg Astronomical Institute, Moscow State University (SAI MSU) (Elbrus region, North Caucasus) are used. The detection and estimation of the Slichter mode is performed according to our developed asymptotically optimal algorithm for data analysis with allowance for the properties of seismic noise and mode features, including the parameters of its splitting. The hypothesis of the constant mode excitation is tested. The most probable periods of the Slichter mode and the values ​​of the splitting parameter are determined, and the statistical reliability of the detection is estimated.