The deformation field of the August 2003 eruption at Piton de la Fournaise, Reunion Island, mapped by ASAR interferometry

Three independent ASAR interferograms spanning the August 2003 Piton de la Fournaise eruption, reveal a 3 by 3 km asymmetric pattern of range changes centred on the Dolomieu crater northern flank. It corresponds to 30 cm of displacement towards the satellite east of the eruptive fissures and 7 cm away from the satellite west of the fissures. Displacements are caused by dyke emplacement below fissures. We model the deformation using a 3D mixed boundary element method for elastic media. This consists of a dyke defined by six geometric parameters and an overpressure gradient. A neighbourhood algorithm was applied to explore this 7 dimensional parameter space. The best-fit model is a 57degrees eastward dipping dyke with a base lying around 1520 m a.s.l. The model provides new evidence of the dyke intrusion - related seaward displacements of the volcano eastern flank.