In his research, Professor Jónsson uses satellite geodesy and surface imaging to study areas threatened by major earthquakes or volcanic activity. Geophysical processes taking place at several kilometers below the earth's surface, such as earthquake fault slip or magma accumulation, result in deformation of the surface that can be measured using geodetic methods. Results of such measurements, along with geophysical modeling, provide vital information about what is going on deep below the surface and help assessing the associated hazards.