Gravimetric evidences of active faults and underground structure of the Cheliff seismogenic basin (Algeria)

Abstract

International audienceThe Cheliff basin (ex El Asnam) is known as one of the most seismic active zone in Algeria and the West Mediterranean region. We can cite the El Asnam earthquake which occurred in 10.10.01980 with magnitude of 7.3. It was generated by a thrust fault with NE–SW sinistral component. Until now, there is a little information about existence of deep active faults, which generate this strong activity. The gravity field is an important resource of information on crustal structure. The aim of this work is giving a reliable geometry of the major faults relative to the kinematics of this region.The results obtained from various filtered maps (derivatives, upward continuation) of the gravity data, were used to generate a structural map of the studied area. Whilst the continuous wavelet transform method can help in automatic detection of elongated structures in 3-D, to estimate their strike direction, shape and depth. It gives a 3-D image or a model of the region and confirms the existence of several faults, localized or inferred, from former geological studies

Identification of deep magnetized structures in the tectonically active Chlef area (Algeria) from aeromagnetic data using wavelet and ridgelet transforms

“…Whereas many others complete the structural information. There is also a good correlation with other geophysical and geological studies (Ouyed et al, 1983;Meghraoui, 1988;Avouac et al, 1992;Bezzeghoud et al, 1995;Aifa et al, 2003;Afalfiz et al, 2009;Beldjoudi et al, 2012;Abtout et al, 2014).…”

“…As this anomaly remains negative, its origin is in the Palaeozoic substratum which is more magnetized and deepest than the Cretaceous one. This is also confirmed by the identification of the sources of the magnetic anomalies in 2-D along the profile and in 3-D (see section 6, below) and by the gravity study of the same area (Idres et al, 1998;Abtout et al, 2014) Some contacts are identified on the gradient map ( Figure 5). The NW-SE one is thrusting in the sinistral way the Boukadir anomaly.…”

“…The wavelet theory can be found in the book of Holshneider (1995) and the theory of its application to potential fields data can be found in Moreau et al, (1997Moreau et al, ( , 1999, Hornby et al, (1999), Sailhac et al, (2000), Sailhac and Gibert (2003), Boukerbout and Gibert (2006), Sailhac et al, (2009), Fedi et al, (2010), Fedi and Cascone (2011) and so on. Many studies illustrate application of this method, for instance we can refer to applications to aeromagnetic and magnetic data (Sailhac et al, 2000;Pouliquen and Sailhac, 2003;Boschetti et al, 2004;Vallée et al, 2004;Yang et al, 2010), electromagnetic data (Boukerbout et al, 2003), spontaneous electrical potential (Gibert and Pessel, 2001;Sailhac and Marquis, 2001, Saracco et al, 2004, Gibert and Sailhac, 2008Mauri et al, 2010) and gravity data (Martelet et al, 2001;Fedi et al, 2004;Cooper, 2006;Chamoli et al, 2011;Abtout et al, 2014).…”

“…Studies of structural geology, seismicity and seismotectonics were therefore strongly developed in this region to better understand the presently active deformation mechanisms (e.g. Rothé, 1950;Perrodon, 1957;Tapponier, 1977;Girardin et al, 1977;Philip, 1983;Thomas, 1985;Ouyed, 1981;Meghraoui, 1988;Yielding et al, 1989; A C C E P T E D M A N U S C R I P T Boukerbout and Abtout, 2000;Domzig et al, 2006;Aifa and Zaagane, 2014;Abtout et al, 2014).…”

Joint modeling of potential-field data and geodynamic interpretation for northeast Algeria

“…Eventual seismic and well data are available but belong to mining and oil companies. Several studies such as Asfirane and Galdeano (1995), Idres (1983), Bournas et al (2003), Abtout et al (2014), Meliani et al (2016) and Boukerbout et al (2018) used gravity and magnetic data (with eventual further processing showing main buried fault directions, main source depths, etc.) to investigate deep crustal structure, but numerical modeling lacks.…”