InSAR analysis of a blind thrust rupture and related active folding: the 1999 Ain Temouchent earthquake (M
w 5.7, Algeria) case study |
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| Authors: | Samir Belabbès Mustapha Meghraoui Ziyadin Çakir Youcef Bouhadad |
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| Institution: | (1) Institut de Physique du Globe de Strasbourg, UMR 7516, Strasbourg, 67084, France;(2) Department of Geology, Istanbul Technical University, Istanbul, Turkey;(3) Centre du Génie Parasismique (CGS), Algiers, Algeria;(4) EOST-IPG Strasbourg, 5 rue René Descartes, 67084 Strasbourg Cedex, France |
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| Abstract: | We study the surface deformation associated with the 22 December 1999 earthquake, a moderate sized but damaging event at Ain
Temouchent (northwestern Algeria) using Interferometric Satellite Aperture Radar images (InSAR). The mainshock focal mechanism
solution indicates reverse faulting with a NE–SW trending rupture comparable to other major seismic events of this section
of the Africa–Eurasia plate boundary. Previously, the earthquake fault parameters were, however, poorly known because no aftershocks
were precisely determined and no coseismic surface ruptures were observed in the field. Using a pair of ERS data with small
baseline and short temporal separation in the ascending orbit we obtained an interferogram that shows the coseismic surface
displacement field despite poor coherence. The interferogram measures four fringes and displays an ellipse-shaped lobe with
∼11 cm peak line-of-sight displacement. The elastic modeling using a boundary element method (Poly3Dinv) indicate coseismic
slip reaching up to 1 m at 5 km depth on the N 57° E trending, dipping 32° NW Tafna thrust fault. The geodetic estimate of
seismic moment is 4.7 × 1017 N m. (Mw 5.7) in is good agreement with seismological results. The elliptical shape of the surface displacement field coincides
with the NE–SW trending Berdani fault-related fold. The consistency between the geological observations and InSAR solution
shed light on the precise earthquake location and related Tafna fault parameters. |
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| Keywords: | InSAR Algeria Earthquake Thrust fault Active folding |
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