The Boukadir active fault-related folding: Active tectonic markers andInSAR analysis (Tell Atlas, Northern Algeria).

The Tell Atlas Mountains are characterized by active tectonics related to
oblique convergence along the Africa-Eurasia plate boundary. The region is
affected by a NNW-SSE to NW-SE transpressive regime, with shortening rates of
2.2 ± 0.5 mm/yr determined from tectonics and paleoseismology, confirmed by
GPS-derived rates of 1-3 mm/yr. The deformation manifests mainly as NE-SW to
E-W trending fault-related-folding structures, affected predominantly Mio-Plio-
Quaternary basins within the Tell Atlas. The Chelif is one such basins which has
experienced a major El Asnam Mw 7.1 seismic event in 1980 along Sara El
Maarouf blind fault. 40 km to the west lies a comparable structure, which is the
Boukadir fault related-folding , responsible for the moderate 2006 Tadjena
earthquake Mw 5.0, causing some damage in Abou El Hassan, Bouzghaïa and
Tadjena villages. The focal mechanism of the 2006 Tadjena earthquake, as well as
that of the 1980 El Asnam event, revealed a reverse fault with a lateral component.
The dislocation model indicated that the Tadjena event is related to a rupture along
a 6 km segment of the entire 35 km Boukadir fault. In this study, we aim to assess
seismic potential of the Boukadir FRF using a plural approach combining geology,
tectonic geomorphology, elastic modeling an Interferometric synthetic aperture
radar (InSAR). Field observations have shown that the Quaternary deposits reveal
progressive unconformities and form terraces along main streams, while the
conglomeratic levels of upper Pliocene are strongly tilted, dipping up to 70° to the
SW where the Boukadir fault is assumed to pass. The study of morphometric
parameters showed a disturbed hydrographic network on the Boukadir fold. We
used InSAR methodology to detect small surface displacements caused by the
Boukadir FRF genesis. PS-InSAR processing of Sentinel data from 2016-2022 in
ascending and descending orbits was employed. Analysis of mean displacement
rates in line of sight (LOS) directions showed subsidence south of the Boukadir
fault system and uplift to the north, consistent with our field investigations and
tectonic geomorphic analysis along the Boukadir reverse fault. Our results reflect
tectonic activity and seismic potential of the Boukadir FRF. They can be integrated
to the Tellian FRF models and contribute to updating the Algerian seismic hazard.