Systematic InSAR monitoring of African active volcanic zones: What we have learned in three years, or an harvest beyond our expectations

We present here a brief overview of some findings and preliminary results obtained after almost three years of systematic monitoring of active volcanic areas in Africa by means of differential synthetic aperture radar interferometry (InSAR). With a database rich of more than 400 SAR scenes of Fogo (Cape Verde), Ol Doinyo Lengai (Tanzania), Nyiragongo-Nyamulagira (DR of Congo) and Mount Cameroon volcanoes, we processed more than 2000 interferograms among which we could detect significant and major geophysical processes: the first dyking event ever captured geodetically in a continental rift (Lake Natron; Northern Tanzania), the co-eruptive deformations of the Lengai, Nyiragongo and Nyamulagira volcanoes, the co-seismic displacements associated to the mb 6.1 February 3rd 2008 Bukavu earthquake as well as the identification of atmospheric induced phase delays over Fogo and Mount Cameroon volcanoes to be attributed to the seasonal oscillations of the inter-tropical convergence zone (ITCZ). These results have been reached given the abundance of data that increases the chances to capture unpredictable events, and capture them with the most favorable interferometric conditions as possible (e.g. in terms of geometrical and temporal baselines that minimized the vegetation-induced decorrelation). They provided strong scientific material as well as tools for hazard assessment.