Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK

A variety of seismic signals representing different physical mechanisms precedes volcanic eruptions. The most meaningful signals are high- and low-frequency earthquakes and volcanic tremor that have tentatively been related to fracturing and magma transport in the volcanic edifi ce. We provide experimental support for this association by reproducing magma migration while recording seismic signals. Opening fractures emit high-frequency acoustic events, while the switch to low frequency and harmonic tremor accompanies the fl ow of the melt in the fractures. Discerning between these seismic signals in nature can signifi cantly refi ne volcanic hazard evaluation.