Characteristics of the Pambak-Sevan-Sunik Fault in the Lesser Caucasus by SAR interferometry

Abstract:

Within the Alpine-Himalaya orogeny belt, the convergence of Arabian–Euraisan collision zone made up the Caucasus mountain belt. The convergence of Arabian-Eurasian Plate is taken up mostly by aseismic shortening and a few on strike-slip faults in the Armenian Highlands, or Lesser Caucasus region. Although the slip rate along the faults in this area are small, they still can generate earthquakes with magnitude up to M=7.5. The 1988 Armenia earthquake, also known as Spitak earthquake, occurred in the western segment of the Pambak-Sevan-Sunik Fault (PSSF). In this study, we focus on the western part of the PSSF and the Alavar Fault which are nearby the Spitak city. As previous studies mentioned, the transition from fault ruptures to folding is associated with a blind thrust that the pattern is not well known. In order to understand the complex structure of this region, we use PS-InSAR technique (Persistent Scatterers Interferometry Synthetic Aperture Radar) and GPS data to detect the recent deformation patterns and the activity of buried structures. The data include L-band radar images collected by the ALOS satellites in ascending orbits between 2006 and 2011 over the study area. Combining with the published focal mechanism and geological data, we try to construct fault planes and an elastic dislocation model to characterize the range of locking depth, interseismic slip rate and slip deficit. The preliminary results provide us insights of how deformation accommodated along the possible hidden branches and how interseismic deformation accumulated along the southern front of Lesser Caucasus. These observations enable us to make the assessment of potential earthquake hazard of this region.