Global Surface Wave Tomography Using Seismic Hum

摘要

Earth's background free oscillations, or seismic "hum" (1-3), are excited continuously and persistently by the ocean and atmosphere. Cross-correlation (CC) analysis of hum signals shows a clear global propagation of background Rayleigh waves, which opens the possibility for global surface wave tomography without referring to earthquakes.rnOne technique known as ambient noise tomography (4) cross-correlates random surface waves (Love and Rayleigh waves) with periods of around 10 s excited by ocean swells. Here, we show that the randomness of the sources of both the hum and ambient noise allows this technique to be applied for hum at much longer periods, 100 to 400 s, to explore the mantle to depths of 500 km.