This paper presents focal mechanism solutions for large volcano-tectonic earthquakes (VTE) at three Kamchatka volcanoes: Shiveluch, Klyuchevskoi, and Plosky Tolbachik followed by comparison between the results in order to distinguish between the principal and the auxiliary nodal plane. The data set included digital seismograms of VTEs not below energy class 7 and depths of focus between zero and 30 km. The solutions were based on the polarities of P-wave first motions using the FPFIT program algorithm. Comparison between the strikes of the first and second nodal planes for large VTEs on each of the three volcanoes has not been sufficient to find the principal plane. Comparison between the dip angles of the first and second nodal planes for large VTEs on each of the three volcanoes and comparison of directions of motion on the first and second planes has enabled us to identify the first nodal plane as the principal and the second nodal plane as the auxiliary.
M. V. Lemzikov (Wed,) studied this question.