HR: 0830h
AN: S51D-0077    [PDF]
TI: Source Mechanism Inversion of Very Long Period Strombolian Eruption Signals at Mount Erebus, Antarctica
AU: * McNamara, S K
EM: mcnamara@ees.nmt.edu
AF: Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Aster, R C
EM: aster@ees.nmt.edu
AF: Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Kyle, P
EM: kyle@nmt.edu
AF: Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AB: Oscillatory, repeatable, very-long-period signals (25 s $>$ T $>$ 5 s) associated with strombolian eruptions of Mt. Erebus, Antarctica have been recorded by near-field broadband seismometers for several years. The eruptions are typically single, large (up to 10-m diameter), explosive bubble decompressions occurring at the surface of a phonolitic lava lake that eviscerate the lake to a depth of approximately 10 m. Associated VLP signals begin several seconds before, and continue for several minutes after, eruptions, becoming indistinguishable as lava lake recovery is achieved. We have performed waveform inversions of high signal-to-noise stacks to recover equivalent point-source moment tensor parameters and associated source time functions. Solutions are obtained by minimizing 2-norm residuals between synthetic and three-component observed seismograms using a modified version of the iterative inversion technique of Lay and Wallace (1995). We allow for varying degrees of source freedom, ranging from pure Mogi (explosive/implosive) to a complete set of six double couples and three single forces. Results suggest a shallow ($\leq$ 200 m) source region and negligible non-volumetric couple and single-force terms. During the VLP coda, the source model evolves in time towards an increasingly subhorizontal resonating crack. We will address the accuracy of using simple half-space Green's functions in such inversions and discuss source mechanism possibilities in terms of slow elastic, dynamic recharge, and other processes.
DE: 7280 Volcano seismology (8419)
DE: 8419 Eruption monitoring (7280)
SC: Seismology [S]
MN: 2003 Fall Meeting