ESA Earth Home Missions Data Products Resources Applications
   
EO Data Access
How to Apply
How to Access
Services
Site Map
Frequently asked questions
Glossary
Credits
Terms of use
Contact us
Search


 
 
 

 

Evolution of Post-Seismic Ground Deformation Observed by SAR Interferometry

Michael Foumelis(1), Issaak Parcharidis(2), Nicolas Voulgaris(1) and Evangelos Lagios(1)

(1) University of Athens, Panepistimioupolis - Ilissia, 15784 - Athens, Greece
(2) Harokopio University of Athens, El. Venizelou 70, Kallithea, 17671 - Athens, Greece

Abstract

Differential Synthetic Aparture Radar interferometry (DInSAR) technique has been extensively applied for the measurement of different geological and geophysical processes. In the field of earthquake studies, the capabilities of SAR interferometry motivated many scientists to develop and apply this technique mainly for the recovering of co-seismic ground deformation signals. However, co-seismic differential interferograms with different temporal cover after the main seismic event may contain variable information regarding the evolution of the post-seismic displacement field. Such analysis was performed in order to investigate the spatio-temporal evolution of ground deformation related to the aftershock sequence of the 07 September 1999 Athens earthquake. In this case study the main shock was followed by a large number of aftershocks which were recorded by a local digital network installed in the epicentral area and remained in operation for a period of 3 months, offering a great opportunity for the common assessment of DInSAR observations and seismological data. Using C-band ERS SAR Single Look Complex (SLC) VV-polarization images acquired in descending mode, four co-seismic differential interferograms were generated covering the period from September to December of 1999 and spanning 16, 33, 68 and 103 days after the occurrence of the main shock. Interferometric results were introduced in a GIS system along with precisely located aftershock epicenters to be further analyzed in terms of magnitude and location of the observed ground deformation maxima. Moreover, the spatial evolution of the interferometric fringe pattrens was analytically examined. As shown, the rate of deformation derived from DInSAR decreases exponentially, following similar trend with post-seismic activity. Additionally, there is a high degree of correlation between the maximum deformation for the various DInSAR pairs and the energy release from the gradual accumulation of aftershocks for these corresponding periods. The propagation of the deformation maxima towards the SE directions is in accordance with the eastward directivity phenomena mentioned in various seismological researches and expressed as well by the progressive migration of the aftershock activity towards the east. Exactly the same trend was revealed by calculating the mean spatial centroids of aftershock epicenters for the corresponding DInSAR epochs. The following pattern of deformation evolution is also recognized by the observed expansion of the displacement field to the east of the epicentral area towards the metropolitan area of Athens as the aftershock sequence evolves. The effort to improve our understanding of earthquake processes by detailed examination of DInSAR results facilitating additional seismological data could lead to a better insight into the evolution of the aftershock sequence and its tectonic implications.

 

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