Persistent Scatterers Interferometry Analysis of the Achaia-Elia Earthquake
Mirek, Katarzyna1; Mirek, Janusz1; Papadimitriou, Eleftheria2; Karakostas, Vassilis2
1AGH University of Science and Technology, POLAND; 2Aristotle University of Thessaloniki, GREECE
An earthquake with magnitude M=6.4 occurred on 06 June 2008 in NW Peloponnessus Greece. Historical seismicity deciphers that at least two earthquakes with Mi6.0 have occurred in the same area in eighteenth and nineteenth centuries. The main shock triggered a number of landslides and rockfalls and toppled old buildings but no significant surface deformation was observed.
A rather intense aftershock activity of small magnitude aftershocks followed with several felt events since they occurred onshore. Relocation performed in previous studies implies that the main rupture occurred on an almost vertical fault segment, having a length of about 24 km with a NNE-SSW orientation. The epicenter of the main shock is located at the southernmost part of the rupture, whereas adjacent smaller fault segments were activated during the course of this activity, probably triggered by stress perturbation caused by the main event.
Aiming in a better understanding of the rupture process on the activated fault segment, geodetic and SAR data were combined with the obtained seismological ones. This paper focuses on SAR data first results.
InSAR images were formed from data collected by ENVISAT satellite of the European Space Agency. The ENVISAT data set is from ascending track 186 and consist of 13 images spanning 19 Feb 2006 - 19 Apr 2009. The data were processed using Doris and StaMPS /MTI software.
In first step we construct interfergoram based on two images 2008.03.30 and 2008.07.13. Generally interferograms were highly decorrelated. Nevertheless regions near the projected fault plain maintain modest coherence and little interference consistent with coseismic activity is identifiable. On the west side of the fault one can see deformation corresponding with maximum approximately 2.5 cm changing on surface. We decided to use PSI technique instead of InSAR. PS mean velocity displacement for the whole period of time (2006.02 to 2009.04) vary from -19.7 to 18.4 mm/yr. One can observed that times series plots of PS points around the fault show characteristic opposite direction of displacement before and after the earthquake.
Authors would like to thank European Space Agency for access to satellite data. The research was supported by the AGH University of Science and Technology in Krakow, Department of Geoinformatics and Applied Computer Science (no. 11.11.140.032).