Earthquake in South California

The Landers earthquake (south California) of 28 June 1992 (magnitude 7.3) presented a surface rupture over 75 km. It was followed three hours later by the Big Bear earthquake (magnitude 6.4). No surface rupture was reported for this later event.
From several images, acquired before and after the earthquake, a differential interferogramme was computed (see figure), which clearly shows the seismic movements due to the earthquake. The banana-shaped fault is clearly visible. Each fringe corresponds to a co-seismic movement of 28.3 mm. The measured precision is 9 mm.
The differential interferogramme was compared with the effects of the movement predicted by an elastic dislocation model (computed by geophysicists of the French Groupe de Recherche an Géodésie Spatiale, GRGS), and the figure shows a very good correspondance between the modelled and the observed pattern of the fringes.

(Massonnet, CNES, Toulouse)

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry