Tilt signals at Mount Melbourne, Antarctica: evidence of a shallow volcanic source

Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in
20 northern Victoria Land, Antarctica. Tilt signals have been recorded on Mount
Melbourne since early 1989 by a permanent shallow borehole tiltmeter
network comprising five stations. An overall picture of tilt, air and permafrost
temperatures over 15 years of continuous recording data is reported. We
focused our observations on long-term tilt trends that at the end of 1997
25 showed coherent changes at the three highest altitude stations, suggesting the
presence of a ground deformation source whose effects are restricted to the
summit area of Mount Melbourne. We inverted these data using a finite
spherical body source, thereby obtaining a shallow deflation volume source
located under the summit area. The ground deformation observed corroborates
30 the hypothesis that the volcanic edifice of Mount Melbourne is active and
should be monitored multidisciplinarily.