Broadband recording of Strombolian explosions and associated very-long-period seismic signals on Mount Erebus volcano, Ross Island, Antarctica

In December 1996 and January 1997, broadband seismometers were deployed on the summit plateau of Mount Erebus at radial distances of 0.7, 1.4 and 1.9 km from the central crater and lava lake. Strombolian explosions at Erebus previously have been observed to produce seismic and acoustic energy between 1 and 6 Hz. New observations document significant energy viith spectral peaks as grave as 20 s. Nearly identical very-long-period (VLP) signals begin similar to 1.5 s prior to explosions, have dilatational onsets and persist for up to 150 s. Similar VLP waveforms were recorded at all three stations, indicating that the seismograms are essentially source-dominated. Particle motions suggest an initial depth for the VLP source of up to several hundred meters, migrating deeper in the course of similar to 15 s. Such explosion-associated VLP signals may indicate a nondestructive lossy resonance or nonlinear fluid-flow excitation within the shallow magmatic system.