The city of Kairouan, the capital of the Aghlabides Dynasty (A.D. 800–909), and its surrounding areas were affected by a damaging earthquake on 8 Rajab 245 Hijri (9 October 859). Contemporaneous accounts by local travelers to the Abassides Califat (A.D. 750–1258) and reported by the chroniclers and historians Al Baghdadi (1980) and Al Tabari (A.D. 838–923) (1967) describe the damage to the city and report that 13 villages experienced extensive destruction, leading to a large number of people homeless. In the city of Kairouan, the dome and other holy places of the Great Mosque (minbar and mihrab), houses, fortifications, and bridges all suffered severe damage. The aqueduct that supplied Kairouan with fresh water from the western mountains was badly damaged at a location about 20 km west of the city. New archaeoseismic field investigations of the aqueduct using laser scanning and radiocarbon dating characterize the damaged features. Recent field investigations in the region taking into account the construction types and the inferred damage distribution suggest a macroseismic intensity reaching IX–X Medvedev–Sponhauer–Karnik scale. The seismotectonic context suggests a seismic source along the major Sbiba east–west-trending transpressive fault that includes the Cherichira, Sfaia, and El Baten folding system near Kairouan. An active fault system affecting late Quaternary units made up of ∼30-kilometer-long thrust-related en echelon folds associated with the east–west-trending fault is identified and characterized as seismogenic at a location about 20 km west of Kairouan.
A B S T R A C TTriassic outcrops in the Atlassic zone of northern Tunisia may be modelled in two ways: salt bodies piercing through Cretaceous terrains or Triassic salt flows stratified within an Albian series. Both models find support from gravity data and are debatable. To evaluate the mass distribution changes with depth, the Bouguer anomaly of the El Kef-Ouargha region was successively decomposed into regional and residual components to construct multiple pseudo-depth slices and apparent density maps. Analyses of gravity lows clearly show a vertical continuity of less dense materials below the Triassic salt outcrops. These features can be explained by salt diapirism during Mesozoic and Cenozoic. Further, gravity data tend to indicate less dense materials below Aptian outcropping in Jebel Aite (Oued Bou Adila); thus suggesting Triassic materials occurring at depth. In addition, dense entities were recognized under MioPliocene and Quaternary deposits, which are thought to correspond to Cretaceous paleoshoals currently collapsed by non-outcropping faults. Our findings lend support to a diapir model intruding overburden rather than the salt glacier model stratified in the Albian series proposed by some authors as the genetic structural model for Triassic material-bearing series in the north of Tunisia.
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