Monitoring rapid temporal change in a volcano with coda wave interferometry

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.

Seismic source displacement by coda wave interferometry at Soufrière Hills Volcano, Montserrat, WI

“…Similar observations from other volcanoes have been reported in literature (e.g. Gret et al, 2005). The early seismogram is highly reproducible, leading to discard the hypothesis of significant variations of the source-time function.…”

Big Sky Carbon Sequestration Partnership

“…Active doublet or coda wave interferometry has the potential to detect changes of the subsurface using the scattered/coda waves, but they cannot tell where the changes occur (Roberts et al, 1992;Gret et al, 2004;Gret et al, 2005;Snieder and Hagerty, 2002;Snieder et al, 2004). Either a highly repeatable active or passive seismic source is recorded.…”

A 3D algorithm based on the combined inversion of Rayleigh and Love waves for imaging and monitoring of shallow structures

“…In turn, such small perturbations can be detected as changes of seismic wave properties based on seismic noise (e.g. Ratdomopurbo & Poupinet 1995;Miller & Smith 1999;Grêt et al 2005;Wegler et al 2006). However, despite considerable efforts in the past, the precise monitoring of the location of subsurface changes has proven to be difficult, meaning that there is a need for novel observational methods to obtain information about the ongoing subsurface changes and their relation to volcanic processes.…”