TY JOUR TI Detecting groups of eigenfrequencies of vertical standing waves in the layered structure of the Earth’s crust KW signal processing technique KW equidistant frequencies KW eigenfrequencies KW P- and S-type elastic waves JO Solar-Terrestrial Physics AU Поляков, А.Р. AU Цэгмэд, Б.. PY 2025 IS 11 PB Институт солнечно-земной физики СО РАН