Eruptive cycles inferred from ground deformation at Piton de La Fournaise - a case study for the Globvolcano project

Due to its high eruptive activity, Piton de La Fournaise is an ideal case study to follow ground deformation associated with eruptive activity. Ground deformation is monitored in the field by the Volcanological Observatory of Piton de La Fournaise. GPS data reveal the presence of two time scales of ground deformation: (1) large short-term displacements (up to 20×10³ mm d^-1 ) monitored a few min to hours prior each eruption (2) and since 2000, small long-term ground displacements recorded during pre-eruptive unrests (0.4-0.7 mm d^-1 of summit inflation) and after major distal eruptions (0.3-1.3 mm d^-1 of summit deflation). The large GPS dataset available to follow the eruptive cycles is particularly useful to validate the remote sensing data as shown by the Globvolcano project. The good correlation between GPS and PSInSAR data recorded during pre-eruptive unrest periods allowed us to validate the ground deformation mapping using PSInSAR data at Piton de La Fournaise. The combination of PSInSar and GPS data, in the future, will give us complementary data to investigate the ground deformation associated with eruptive cycles on a larger space scale and thus better constrain the deformation sources.