Description: Re-examination of marine geophysical data from the continental margin of West Morocco reveals a broad zone characterized by deformation, active faults and updoming offshore the High Atlas (Morocco margin), situated next to the Tafelney Plateau. Both seismic reflection and swath-bathymetric data, acquired during Mirror marine geophysical survey in 2011, indicate recent uplift of the margin including uplift of the basement. This deformation, which we propose to name the Atlantic Atlas tectonic arch, is interpreted to result largely through uplift of the basement, which originated during the Central Atlantic rifting stage - or even during phases of Hercynian deformation. This has produced a large number of closely spaced normal and reverse faults, “piano key faults”, originating from the basement and affecting the entire sedimentary sequence, as well as the seafloor. The presence of four terraces in the Essaouira canyon system at about 3500 meters water depth and “piano key faults” and the fact that these also affect the seafloor, indicate that the Atlantic Atlas is still active north of Agadir canyon. We propose that recent uplift is causing morphogenesis of four terraces in the Essaouira canyon system. In this paper the role of both Canary plume migration and ongoing convergence between the African and Eurasian plates in the formation of the Atlantic Atlas are discussed as possibilities to explain the presence of a tectonic arch in the region. The process of reactivation of passive margins is still not well understood. The region north of Agadir canyon represents a key area to better understand this process.

Description: Highlights • We document marine forearc deformation in the Northern Chile seismic gap. • Upper-plate normal faulting off Northern Chile locally extends close to the trench. • Normal faults indicate that past earthquakes may reached the shallow plate-boundary. Abstract Seismic rupture of the shallow plate-boundary can result in large tsunamis with tragic socio-economic consequences, as exemplified by the 2011 Tohoku-Oki earthquake. To better understand the processes involved in shallow earthquake rupture in seismic gaps (where megathrust earthquakes are expected), and investigate the tsunami hazard, it is important to assess whether the region experienced shallow earthquake rupture in the past. However, there are currently no established methods to elucidate whether a margin segment has repeatedly experienced shallow earthquake rupture, with the exception of mechanical studies on subducted fault-rocks. Here we combine new swath bathymetric data, unpublished seismic reflection images, and inter-seismic seismicity to evaluate if the pattern of permanent deformation in the marine forearc of the Northern Chile seismic gap allows inferences on past earthquake behavior. While the tectonic configuration of the middle and upper slope remains similar over hundreds of kilometers along the North Chilean margin, we document permanent extensional deformation of the lower slope localized to the region 20.8°S–22°S. Critical taper analyses, the comparison of permanent deformation to inter-seismic seismicity and plate-coupling models, as well as recent observations from other subduction-zones, including the area that ruptured during the 2011 Tohoku-Oki earthquake, suggest that the normal faults at the lower slope may have resulted from shallow, possibly near-trench breaking earthquake ruptures in the past. In the adjacent margin segments, the 1995 Antofagasta, 2007 Tocopilla, and 2014 Iquique earthquakes were limited to the middle and upper-slope and the terrestrial forearc, and so are upper-plate normal faults. Our findings suggest a seismo-tectonic segmentation of the North Chilean margin that seems to be stable over multiple earthquake cycles. If our interpretations are correct, they indicate a high tsunami hazard posed by the yet un-ruptured southern segment of the seismic gap.

Description: The continental margin of Mozambique formed during the initial dispersal of Gondwana about 180 Ma. Due to the lack of deep seismic and dense potential field data, many details of the timing and geometry of the early breakup in this region remained unknown to date. To close this gap, a research project (MoBaMaSis (“Mozambique Basin Marine Seismic Survey”) with the French research vessel R/V Marion Dufresne II was conducted in 2007. This paper presents the results of P-wave, magnetic and 2D-gravity modelling along two parallel seismic refraction profiles between 37° and 41° E, crossing the Mozambique rifted margin. The crust shows the characteristics of normal to slightly thickened oceanic crust. A lower crustal highvelocity- body with P-wave-velocities of 7.0–7.5 km/s is observed along both profiles. Its origin is discussed in the context of upper mantle convection and thermal properties. The existing magnetic anomaly identifications have been extended to older ages. We postulate that the oldest oceanic crust near the Central Mozambique continental margin has been formed around M41n (166 Ma). Closer to the coast a pronounced negative magnetic anomaly exists that we interpret to coincide with the continent–ocean-transition. This implies that the position of the continent–ocean-transition is located significantly closer to the shoreline than proposed before.