3D Geometry of normal faults in arheologically layered system : Analoguemodelling and seismic examples

International audienceGeometry of normal faults, within the sedimentary cover, may be influencedby different parameters such as the presence, position and efficiencyof décollement levels, the amount, direction and velocity of extension,and the rate of synkinematic sedimentation. These parametershave already been studied at different scales in field approach, analogueand numerical modelling. The effect of several décollement levels hasbeen studied at lithospheric scale to better understand the deformationprocesses between surface and depth. At the scale of single structure ina sedimentary basin, previous analogue modelling only studied the effectof a determined geometry of a fault on the synkinematic sedimentation.Here we used analogue modelling to analyse the 3D geometry of asingle structure in a domain with three prekinematic décollement levels,analogue of salt, shale or under-compacted level. These experiments resultin flat and ramp geometry in relation with décollement level andthe pattern of the deformation depends here mainly on the velocity andamount of extension. The results of the experiments were compared toseismic examples in order to better interpret typical fault setups. Oneof the key points is that the geometry of normal faults displays largevariations both in direction and dip, only in pure extensive regime, relatedto the presence of décollement levels, and not associated with anyglobal/regional variation of extension direction