Volcanic tremors and shocks associated with eruptions at Etna (Sicily), September 1980

摘要: Abstract Three strong ash eruptions, superimposed on an otherwise rather quiet state of volcanic activity, took place from the northeast crater Etna during September 1980. The eruptions lasted only a few hours and were associated with increase in amplitudes tremors by factor 10 compared mean value preceding months. Special emphasis tremor analysis was given to eruption 26, time function amplitude envelope follows mathematical which resembles behaviour mechanical oscillator resonant period about 300 s. A detailed spectral before, after reveals factors seem be ascent descent sources magma columns. turbulent eruptive flow apparently is concentrated dykes pipes. Their eigenvibrations are observed as peaks small bandwidth, smoother spectrum without eruption. An seismicity shows maximum August epicenters clustering along NW-SE direction.