Isabelle Panet honoured by the French Académie des Sciences

Isabelle Panet studied at the Ecole Polytechnique from 1997 to 2000, before joining the Institut National de l’Information Géographique et Forestière (IGN). She specialised in geodesy and internal geophysics, and obtained her PhD in 2005 at the IPGP, followed by a post-doctorate at the Geographical Survey Institute of Japan from 2006 to 2008. She then worked at the IGN’s Geodesy Research Laboratory, before joining the IPGP’s Geodesy team, which she has headed since 2019. Her work focuses on the use of satellite gravity observations to detect the gravitational signatures of mass redistributions deep inside the Earth, which are often inaccessible using other geophysical methods. This is an original way of characterising dynamic processes linked to the seismic cycle and mantle convection. Her approach includes the development of methods for analysing the Earth’s gravity field to improve the resolution of internal sources, and the geophysical interpretation of the signals they produce. Isabelle Panet is also involved in the scientific specification of future gravity missions for various space agencies (CNES, ESA, NASA), with the aim of continuing and improving the observation of the gravity field from space.

The winning project involves studying variations in the gravity field around the Pacific Ring of Fire and identifying signals associated with deep movements likely to have an impact on seismicity of subduction zones. At the interface between a continental plate and an oceanic plate that plunges into the mantle, these geological boundaries produce the largest earthquakes observed on Earth. Understanding the processes that trigger them and identifying pre-seismic signals
remains a major challenge, and one that requires us to better constrain the role of the deep dynamics of subducting plates in the mantle. These asismic deformations of subducted plates are still inaccessible today because of an observational gap. The project proposes to document them through the impact of associated mass redistributions on the Earth’s gravity. The analysis methods developed by Isabelle Panet have enabled us to identify deep-rooted variations in gravity in the months preceding the 11 March 2011 earthquake in Japan (Mw 9.0) and the 27 February 2010 earthquake in Chile (Mw 8.8). These pre-seismic signals suggest sudden asismic deformation of the plates in the upper mantle around 150-300 km below the surface, whose migration towards the surface could have created favourable conditions for the triggering and propagation of these very large ruptures.