Imaging the Low Dip Onset of the Gibraltar Arc Subduction in the Gulf of Cádiz Using OBS Receiver Functions

Abstract

Using P and S‐wave receiver function analysis we investigate the lithospheric structure in the Gulf of Cádiz through a combination of ocean‐bottom seismometers and onshore seismic stations located in southwest Iberia and northwest Africa. By applying common conversion point migration with custom earth models accounting for the marine sediment layer, we imaged the Gibraltar–Alboran slab in a low‐dip subduction geometry. Both the oceanic Moho and lithosphere‐asthenosphere boundary were identified, picturing an oceanic lithosphere approximately 125 km thick. The onset of subduction occurs near the Horseshoe fault, at approximately 10 ° W, where the slab begins to descend. At ∼ 4.5 ° W, the slab bends into an almost vertical direction, coincident with the location of intermediate‐depth seismicity. Beneath the western Gibraltar Arc the underthrusted paleomargins of both Iberia and Nubia appear to be fully preserved and still connected to a narrow section ( ∼150 km) of oceanic crust.