Three distinct regimes of volcanic tremor associated with the eruption of Shishaldin Volcano, Alaska 1999

摘要: Tremor signals associated with the eruption of Shishaldin Volcano on 19 and 23 April 1999 were strongest recorded anywhere in Aleutian Arc by Alaska Observatory (AVO) its 10-year history. Reduced displacements (DR) reached cm2 43 April. During activity, DR spectral data a frequency resolution 0.1 Hz computed put World Wide Web every 10 min. These are analyzed here. The general temporal patterns seismicity these events similar, but eruptions their effects quite different. event is known to have culminated sub-Plinian phase, which ejected ash an altitude 16 km. Despite higher amplitudes largest hotspot from satellite data, produced little reaching only 6 km altitude. For several hours prior phase April, tremor peak 1.3 intensified. increased 4–8 Hz. However, 15 h after eruption, three episodes stronger occurred lower 1.0-Hz peak, alternating weaker 1.3-Hz peak. transitions correspond DR=~8 cm2. Although strong levels than pressure sensor show that Strombolian explosions occurred. suite observations suggests distinct regimes may slug flow, bubbly sustained eruptions, or cyclic change source parameters (e.g., geometry, sound speed, ascent rate). This behavior at during sequence, we not aware similar other volcanoes.