Internal structure of Erebus volcano, Antarctica imaged by high‐resolution active‐source seismic tomography and coda interferometry

Abstract

[1] Erebus volcano, Antarctica has hosted a persistent convecting phonolite lava lake for over 40 years. The lake produces small (VEI 0-1) Strombolian eruptions resulting from gas slugs rising through the upper conduit system. High-resolution (to scale lengths of several hundreds of meters) three-dimensional P-wave tomographic velocity images were obtained to a depth of approximately 600 m below the volcano surface. Data were collected using 91 seismographs deployed over an approximately 4 by 4 km area of the summit region. Seismic illumination was provided by 12 chemical shots emplaced in shallow snow and ice boreholes. P-wave direct arrival travel-time measurements were used to invert for strong velocity anomalies (with spatial variations in V p exceeding AE1 km/s) associated with the uppermost few km. Shallow anomalies correlate with fumarolic ice caves, a prominent radial chilled dike, and ring structures associated with the caldera rim. Conduit structures feeding the lava lake and other vents within the Inner Crater are evidently too small (e.g., less than many 10 s of meters) to be imaged under the resolution limits of this experiment. However, combined velocity and coda interferometry scattering intensity images identify near-summit regions with both low velocity and high scattering that are candidates for magma accommodation. Results indicate a nonaxisymmetric near-summit magmatic system that is likely constrained by heterogeneous structures in the uppermost volcano. The most extensive volume of near-summit magma likely resides approximately 500 m NW of the active Inner Crater vents at depths of 500 m and more below the surface.Citation: Zandomeneghi D., R. Aster, P. Kyle, A. Barclay, J. Chaput, and H. Knox (2013), Internal structure of Erebus volcano, Antarctica imaged by high-resolution active-source seismic tomography and coda interferometry, J. Geophys.

Dynamics of the Mount Nyiragongo lava lake

“…To our knowledge there is no estimation in the literature for Mount Nyiragongo's conduit diameter, contrary, for instance, to Mount Erebus, where it has been suggested to range from 4 to 10 m [Calkins et al, 2008;Zandomeneghi et al, 2013]. However, on 3 June 2011 (at around 08:00 P.M.) we witnessed a remarkable 25 m drop in the lava lake level in less than 1 min (a time lag representing an upper bound given a gas plume temporarily hindered visibility of the lava lake), which involved a magma volume estimated at 1.0 × 10 6 m 3 .…”

“…To constrain the conduit diameter, we consider values of 7.5 m, 10 m, 12.5 m, and 15 m, which range within the reported values for basaltic volcanoes [Head and Wilson, 1987;Harris and Ripepe, 2007;Keating et al, 2008;Molina et al, 2012;Zandomeneghi et al, 2013].…”

Multiple scattering from icequakes at Erebus volcano, Antarctica: Implications for imaging at glaciated volcanoes

“…Furthermore, it is observed to be frequency dependent, exhibiting behavior similar to that observed at Pinon Flat [ Margerin et al , ]. This may be representative of scattering from near‐surface structures such as bodies of magma or ash layers [ Zandomeneghi et al , ].…”

“…(a) Map of the upper edifice of Erebus volcano with some principal geographic and geological features and showing the locations of the ESA (inset), the permanent MEVO [ Aster et al , ], and temporary Tomo Erebus stations [ Zandomeneghi et al , ]. (b) Fifty‐five hours of continuously recorded data on station ESA1, showing transient short‐period signals caused by multiple near‐summit icequakes (see also Figure ).…”

Hotspots and Mantle Plumes

“…Recently, Zandomeneghi et al (2013) determined a high-resolution (to scale lengths of several hundreds of meters) 3-D P-wave tomography to a depth of ~ 600 m below the Erebus volcano surface using data recorded by 91 seismometers deployed over an ~ 4 by 4 km area of the summit region from 12 chemical shots emplaced in shallow snow and ice boreholes. Their results revealed detailed structures of the near-summit magmatic system of the Erebus volcano.…”