Active folding in the Tenes region (Tell Atlas, Algeria): modelling the 1922 earthquake fault-related fold (Mw 6.2)

Abstract

We study the Tenes Abou El Hassan (TAEH) fault-related fold of the Tell Atlas (the site of the 1922 Mw 6.2 earthquake) using field investigations combined with satellite image processing. The 1922 earthquake is also revisited through previous reports, publications and contemporaneous newspapers in order to locate the area of maximum ground motion and its relation to the active TAEH fault-related fold. The analysis of high-resolution (0.5 m) satellite imagery (panchromatic Pleiades tri-stereo images) allows the accurate study in tectonic geomorphology and the characterization of active and seismogenic deformation. High-resolution DEMs obtained from Pleiades images highlight alluvial and marine terraces with cumulative uplift during the Upper Pleistocene–Holocene period and allowed the identification of geomorphological markers along the active fold with recognition of complex tectonic structures. The fault-related fold is modelled using both elastic (Okada 1992) and kinematic (Trishear) approaches using balanced cross-sections that reveal 1.2 mm/year shortening rate during the Upper Pleistocene–Holocene. Uplift rate calculated using marine and alluvial terrace altitudes is ~0.3 mm/year during the Upper Pleistocene along the Allalah Quaternary basin and the coastal zone reaching ~1 mm/year during the Holocene. The earthquake geology and correlation between surface deformation and seismotectonic modelling provides additional constraints on the 1922 earthquake fault parameters and related seismic hazard assessment in the Tell Atlas of Algeria.