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Erebus Putative Seismic-Tremor Infrasound observed at I55US on day 260, 2002, Sep.17

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

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  1. 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

  2. Eight sensor array at I55US with Erebus volcano

  3. Erebus seismic tremor infrasound 9/17/02 Trace Velocity 0.339 Km/sec Azimuth 339 deg. Maximum peak- To-peak Amp 0.02 Pascal

  4. Abs(fft) tremor infrasound 05:05 to 05:05:30, 260 0.86 sec

  5. Erebus Tremor Infrasound 9/17/02,05:05:30-05:06:00 UT Velocity 0.308 km/sec Azimuth 341 deg.

  6. Abs(fft) tremor infrasound 12:25 to 12:26 UT day 260 0.89 sec

  7. abs(fft) Erebus infrasound 13:05 to 13:06, day 260 1.08 sec

  8. MCCM detector plot Erebus infrasound Sept 17,2002 12:00 to 13:00 UT MCCM Trace Velocity 340 deg. Azimuth

  9. 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

  10. Phase-aligned overlay inner three sensors of tremor infrasound day 260, 04:01 to 04:10 UT

  11. 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

  12. Scatter diagrams for velocity, slowness and wavenumber space for tremor inf. Day 260

  13. MCCM Detector plot, I55US, 9/17/02 filtered data (0.7 to 10 Hz) inner sensors only MCCM Velocity 340 deg. Azimuth

  14. Azimuth of Arrival for 24 hours 9/17/02 I53US 340 deg.

  15. Trace Velocity I53US 09/17/02 0.350 km/s 0.30 km/s

  16. MCCM detector plot, I55US 8/24/02, filtered (0.7 to 10 Hz) 340 deg.

  17. MCCM plot I55US 6/03/03 filtered (0.70 to 10 Hz) 340 deg.

  18. Tremor signal detector plot day 260 04:00 to 05:00 UT

  19. Tremor signal detector plot day 260 05:00 to 06:00 UT

  20. 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

  21. Impulsive Signals from Strombolian-type eruptions from the lava lake in the Erebus Crater Phase-aligned overlay of 8 sensor traces

  22. Erebus Crater with lava lake eruption

  23. Strombolian type Erebus signal 8/13/2002 Seconds

  24. 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.

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