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The explosive activities of the volcanoes Stromboli (Aeolian Islands, Italy) and Yasur (Tanna Island, Vanuatu) produce low-frequency seismic signals. Several types of such signals were identified both on Stromboli (Types Is and 11s) and on Yasur (Types Iy, IIy, and IIIy). The dominant Erequencies of these signals fall generally between 1 and 3 Hz although sometimes frequencies in the range 3- 6 Hz also exist. The two volcanoes display similar seismic characteristics: the seismic signal associated with the strombolian explosion is accompanied by a forerunner signal that occurs several seconds before eruption and which corresponds to the time separating the formation of the gas pocket at different levels in the magmatic column and its reaching the surface. The similar spectral characteristics of the volcanic background seismic noise and the discrete signals suggest a common source.