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Erebus Putative Seismic-Tremor Infrasound observed at I55US on day 260, 2002, Sep.17. Charles R. Wilson, John V. Olson and Daniel L. Osborne, Geophysical Institute, University of Alaska at Fairbanks, Alaska October 17, 2003. Eight sensor array at I55US with Erebus volcano.
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Erebus Putative Seismic-Tremor Infrasound observed at I55US on day 260, 2002, Sep.17 Charles R. Wilson, John V. Olson and Daniel L. Osborne, Geophysical Institute, University of Alaska at Fairbanks, Alaska October 17, 2003
Erebus seismic tremor infrasound 9/17/02 Trace Velocity 0.339 Km/sec Azimuth 339 deg. Maximum peak- To-peak Amp 0.02 Pascal
Erebus Tremor Infrasound 9/17/02,05:05:30-05:06:00 UT Velocity 0.308 km/sec Azimuth 341 deg.
Abs(fft) tremor infrasound 12:25 to 12:26 UT day 260 0.89 sec
MCCM detector plot Erebus infrasound Sept 17,2002 12:00 to 13:00 UT MCCM Trace Velocity 340 deg. Azimuth
MCCM detector plot for random noise on all eight sensors at I55US Random Noise Sensor Number 1 MCCM value; 0 to 1 Trace Velocity Azimuth of arrival One hour of time
Phase-aligned overlay inner three sensors of tremor infrasound day 260, 04:01 to 04:10 UT
Uncertainty in velocity and azimuth fortremor infrasound day 260, 04:01 to 04:10 Velocity = 307 m/sec +/- 1.35 m/sec Azimuth = 340 +/- 0.25 deg
Scatter diagrams for velocity, slowness and wavenumber space for tremor inf. Day 260
MCCM Detector plot, I55US, 9/17/02 filtered data (0.7 to 10 Hz) inner sensors only MCCM Velocity 340 deg. Azimuth
Trace Velocity I53US 09/17/02 0.350 km/s 0.30 km/s
MCCM detector plot, I55US 8/24/02, filtered (0.7 to 10 Hz) 340 deg.
Continuous-Type Erebus “tremor” signals • During the year 2002 four episodes have been found in the I55US data set of very low amplitude, continuous-type infrasound from an average azimuth of 340 +/- 0.78 deg, with an average trace velocity of 329.50 +/- 3.0 m/sec • The average amplitude of these signals is 0.01 Pa, with a duration up to 5 hours
Impulsive Signals from Strombolian-type eruptions from the lava lake in the Erebus Crater Phase-aligned overlay of 8 sensor traces
Statistics of impulsive signals • 182 Erebus signals received at I55US • Period April 2002 to March 2003 • Average trace vel = 320.5 +/- 6.32 m/sec • Average Azimuth = 336.5 +/- 0.39 deg • The impulsive signals were filtered in the passband 0.70 to 10 Hz to eliminate the microbarom background • Impulsive signals are coherent over the entire 8 sensor array of aperture 1.9 km.