ULTRASONIC PRECURSOR SIGNALS OF SEISMIC EVENTS REVEALED ON VOLCANO STROMBOLI

Ultrasonic bursts preceding low-frequency (seismic) signals were detec ted on the Volcano Stromboli (Italy) for 365 over 579 seisms, by the u se of three sensors for ultrasonic waves. We considered precursor sign als the impulsive ultrasonic waves detected on the volcanic surface fr om about 5 minutes before the seism, during periods of low volcanic an d acoustic activity. Since the discovered signals are precursors of se isms with the highest reliability, we can use them for an experimental study of the predictability of, seisms in a geophysical model.