Fig. 4
From: Earth’s free oscillations excited by the 2011 Tohoku earthquake recorded in multiple GPS networks
The Fourier power spectra of OSE stack for the spheroidal modes from the GEONET network with 968/910 stations, for: a U-component for l = 1 (m = − 1, 0, 1); b U-component for l = 2 (m = − 2, − 1, 0, 1, 2); c N/E-component for l = 2 (m = − 2, − 1, 0, 1, 2); d N/E-component for l = 3 (m = − 3, − 2, − 1, 0, 1, 2, 3). The vertical lines indicate the PREM eigenfrequencies of the spheroidal fundamental modes