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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L06304, doi:10.1029/2004GL021143, 2005

Monitoring rapid temporal change in a volcano with coda wave interferometry

Alexander Grêt

Center for Wave Phenomena and Department of Geophysics, Colorado School of Mines, Golden, Colorado, USA


Roel Snieder

Center for Wave Phenomena and Department of Geophysics, Colorado School of Mines, Golden, Colorado, USA


Richard C. Aster

Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA


Philip R. Kyle

Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA


Abstract

Multiply–scattered waves typically dominate the late part of the seismic coda in local earthquake seismograms. Small medium changes that have no detectable influence on the first arrivals are amplified by multiple scattering and may thus be readily observed in the coda. We exploit this idea using Coda Wave Interferometry to monitor temporal changes at Mount Erebus Volcano, Antarctica. Erebus is one of the few volcanoes on Earth with a long–lived convecting lava lake. Large exsolved gas bubbles generate impulsive Strombolian explosions that provide a repeating seismic source of seismic energy propagating through the strongly scattering geology of the volcano. We examined these signals during a particularly active eruptive two–month period between December, 1999 and February, 2000. Early seismograms are highly reproducible throughout this period. During the first month this is also the case for the coda. Approximately midway through this period, however, the seismic coda decorrelates rapidly over a period of several days. This indicates a rapid change in the scattering properties of the volcano, likely reflecting subtle changes in the near–summit magma/conduit system that would not be discernible using direct– or single–scattered seismic wave methods.

Received 29 July 2004; accepted 7 February 2005; published 18 March 2005.

Index Terms: 0935 Exploration Geophysics: Seismic methods (3025, 7294); 5102 Physical Properties of Rocks: Acoustic properties.

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Citation: Grêt, A., R. Snieder, R. C. Aster, and P. R. Kyle (2005), Monitoring rapid temporal change in a volcano with coda wave interferometry, Geophys. Res. Lett., 32, L06304, doi:10.1029/2004GL021143.