The main objective of the project is to better understand the complex space and time evolution of postseismic transient processes to better assess their link with the coseismic processes and how they contribute to the stress redistribution, which might lead to the generation of catastrophic seismic sequences. The originality of the project is to focus on the shorter time scale of the postseismic phase, the transition from the co- to postseismic (i.e. early postseismic, from minutes to early days) and to test to what extent the better description and knowledge of the co- and early postseismic deformation help to resolve the longer time-scale postseismic deformation (months - years).

Within the project we target several crucial questions concerning the co- to postseismic transition and postseismic processes.

  • We do not know if generic properties can be established for earthquakes and their spatial relations with postseismic deformation (aseismic and aftershocks, correlated or anti-correlated in space and time).
  • The precise transition between the co- and postseismic phases has been very rarely imaged and remains essentially unknown.
  • We need to explore the physics that may account for various slip behavior on the fault (seismic, aseismic, fast and slow slips), and whether a universal law can explain afterslip from minutes to years.
  • Going from the short time scale to the longer time scale, we expect new transitions to take place, or some degree of overlap between the three main processes; afterslip, viscoelastic relaxation, and poroelastic relaxation.

Although earthquake and deformation observations have increased greatly in recent years, we have to carefully identify the most suitable targets to answer the scientific objectives described here. This is a real challenge, because we cannot disperse our efforts on earthquakes that will later prove to be inadequate.

We believe that the modern era of geodesy is now appropriate to investigate the questions posed concerning the understanding and the space/time relations between coseismic, early postseismic and later postseismic deformation. Our ability to resolve deformation accurately over a wide range of frequencies, amplitudes and spatial scales is critical for understanding the underlying processes (WP 1). Concerning the analysis and interpretation of the data, our work is divided into two tasks: Improving the resolution and robustness of slip imagery (WP 2) and increasing our knowledge on the postseismic processes (WP 3).