Seismic 1/f Fluctuations from Amplitude Modulated Earth's Free Oscillation

We first report that the seismic data from around the world yield 1/f fluctuations if we exclude giant earthquakes. We investigate the origin of this 1/f fluctuation based on our recent proposal: 1/f noise is amplitude modulation and demodulation. We speculate that this amplitude modulation is encoded by the resonance with the Earth Free Oscillation (EFO) and demodulated by fault rupture. We partially demonstrate this scenario by analyzing the EFO eigenmodes. We briefly describe possible verifications of our theory of 1/f fluctuations based on EFO.