Deformation between 1989 and 1997 at Piton de la Fournaise volcano retrieved from correlation of panchromatic airborne images

We processed two panchromatic airborne images in the attempt to measure deformation on Piton de la Fournaise volcano between 1989 and 1997. Piton de la Fournaise erupted three times during 1989-1997 with fissures opening near Dolomieu summit crater. During this period no Synthetic Aperture Radar Interferometry data were available and only few geodetic points surveyed the summit crater. We therefore, apply for the first time the subpixel image-correlation technique on airborne images for monitoring ground deformation on Piton de la Fournaise volcano. Correlogram analysis reveals cumulative deformation in the summit area. We observe ESE spreading of the summit caused by the inflation-deflation cycle during 1989-1997. We calculated relative ground displacement along both sides of the main eruptive fissures, finding a maximum of 1.8 (+/- 0.42) m opening. Direct comparison between deformation retrieved by correlation and available geodetic data at four locations shows qualitative agreement. We demonstrate the potential of subpixel image correlation technique, using panchromatic airborne images, for deformation monitoring on volcanoes. We also illustrate the capability of this technique for remote lava flow mapping.