HR: 1330h
AN: V52B-0430    [PDF]
TI: Description and Location of Tremor at Mt. Erebus Volcano, Antarctica
AU: * Ruiz, M C
EM: mruiz@ees.nmt.edu
AF: Dept. Earth \& Environmental Science, N.M. Inst. of Mining \& Technology, 801 Leroy Place, Socorro, NM 87801
AU: * Ruiz, M C
EM: mruiz@ees.nmt.edu
AF: Departamento de Geofisica. Escuela Politecnica Nacional, Ladron de Guevara s/n, Quito, 17-1-2759 Ecuador
AU: Aster, R C
EM: aster@ees.nmt.edu
AF: Dept. Earth \& Environmental Science, N.M. Inst. of Mining \& Technology, 801 Leroy Place, Socorro, NM 87801
AU: Kyle, P R
EM: kyle@nmt.edu
AF: Dept. Earth \& Environmental Science, N.M. Inst. of Mining \& Technology, 801 Leroy Place, Socorro, NM 87801
AU: Wilson, D C
EM: davew@ees.nmt.edu
AF: Dept. Earth \& Environmental Science, N.M. Inst. of Mining \& Technology, 801 Leroy Place, Socorro, NM 87801
AB: From June 2000 till July 2003, 322 distinct episodes of tremor activity have occurred at Mt. Erebus volcano, Antarctica in three extended periods (A. June 2000-October 2001; B. January-December 2002; C. January-July 2003). Period A was characterized by episodes with short duration and small amplitudes (except for a peak in February, 2001). Period B contains the largest amplitudes, reaching a maximum ground velocity of 97.8 microns/s at 0.7 km from the crater on May 21, 2002 (with a reduced displacement of 92.6 cm$^{2}$, assuming a source at sea level (3.7 km below the summit), and purely body waves). The May, 2002 activity climax was followed by long-lasting and smaller-amplitude tremor episodes lasting until December 2002, and followed later by period C. Erebus tremor exhibits a large variation in duration, amplitude, and frequency content. Three general categories of tremor have been recognized based on predominant characteristics: harmonic (91%), chaotic (6%) and rapid-fire (3%). Within single episodes, events frequently show transitions between these types. The tremor shows no clear association with activity observed in the persistent convecting phonolite lave lake or adjacent vents. Since tremor commenced strombolian eruption frequency has declined, although the cause of this is unknown and is probably related to changes in upper-conduit geometry and not to the tremor. The precise location of these non-transient signals is difficult, and source locations were estimated using several different methods. A first-order approximation was carried out by contouring isoseismal curves and fitting real and theoretical attenuation curves. We also applied envelope cross-correlation, semblance, and spectrogram cross-correlation techniques. Results from the best harmonic and rapid-fire tremor source solutions suggest the presence of at least two distinct deep tremor sources located between 3 to 9 km beneath the summit plateau. We will discuss assumptions, methodology, and implications of the activity and source locations for the evolving dynamics of Erebus.
DE: 7280 Volcano seismology (8419)
DE: 8400 VOLCANOLOGY
DE: 8419 Eruption monitoring (7280)
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting