Event Detection and Spectral Analysis of Lava Lake and Inner Crater Seismic Activity at Erebus Volcano Observed with a Dense Three-Component Near-Summit Seismic Array

Erebus volcano on Ross Island, Antarctica has maintained an erupting phonolitic lava lake for at least five decades. During active periods, the lava lake hosts large (up to ~10-m diameter) gas slugs rising through the conduit that create impulsive Strombolian eruptions and produce very long period (VLP) signals on broadband seismograms. We combine near-summit broadband observations and data from a 100-station three-component short-period (4.5 Hz) ETS array deployed in an approximately 3 by 3 km region around the main crater of Mount Erebus during December 2008. Lava lake eruption template events are identifiable on broadband seismograms by a characteristic VLP spectral signature of nonharmonic modes between 0.033 and 0.2 Hz. Multi-channel and multi-station waveform and envelope matched filter correlations are performed across the short-period network using these events, and correlation values that are at least 3 standard deviations are extracted into a working inner crater event catalogue, with a characteristic template correlation across the ETS array yielding several thousand event detections over 16 days. We examine trends in location, occurrence, and spectra to identify event families for further interpretation. Waveform envelope correlations are analyzed to identify seismic sources from the inner crater region that are not associated with magma transport, or that at least lack a VLP signature. Investigating the various event families that transpire in the inner crater region contributes to improved characterization and understanding of the seismogenic behavior of the lava lake degassing system and assists in the creation of a workflow that can be applied in volcanic and other circumstances that generate prolific low-level impulsive seismicity.