Purpose. The paper’s purpose consists in determining the source mechanism of 29.09.2017 earthquake near Stebnyk (21h46m8,4s, = 49,34˚, λ = 23,49˚, h = 1,9 км, MD = 2,9) using two methods – from polarities of first P-wave arrivals and by inversion of wave forms registered at a limited number of stations. Methodology. Seismic waves in the inhomogeneous medium represented by horizontally layered elastic structure are calculated using the matrix method. Expressions derived for the field of displacements on the upper surface are used for the determination of seismic moment tensor rate by isolating only direct P-waves. Also, the source mechanism is determined from polarities of first P-wave arrivals. Result. In the paper, a new method is presented for determination of earthquake source mechanism by inversion of only direct P-waveforms registered at only a limited number of stations and from polarities of first P-wave arrivals at seismic station. The conclusion is drawn out that mechanism simultaneously determined from polarities of first P-wave arrivals is more reliable. Correlation hogging of the earthquake characteristics and its source mechanism with tectonic setting of the region enables to associate the earthquake with thrusting of second order within the extent of allochtonous part of the Sambir nappe. Originality. The inversion of waveforms of only direct P-wave, proposed in the paper, make it possible to determine the focal mechanism of the earthquake by using the data of a small number of stations. It is especially important in regions with relatively low levels of local seismic activity, which include Precarpathians. The mechanism of the earthquake near Stebnyk of 29.09.2017 is one of the first, determined within the extent of the Сarpathian Foredeep; and comparison of the mechanism with the geological structure data of the region made it possible to ascertain the probable tectonic preconditions of the earthquake and to associate it with landslide near the city of Stebnyk. Practical significance. One of the nodal planes of the source mechanism determined in the paper corresponds to rupture plane of the earthquake which supposedly triggered the ecological catastrophe – disastrous landslide near the city of Stebnyk on 29.09.2017 at approximately 21h47m0.0s.
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