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- Gondwana breakup: messages from the North Natal ValleyPublication . Moulin, Maryline; Aslanian, Daniel; Evain, Mikael; Lepretre, Angelique; Schnurle, Philippe; Verrier, Fanny; Thompson, Joseph; De Clarens, Philippe; LEROY, Sylvie; Dias, Nuno; Afilhado, Alexandra; Apprioul, R.; Bronner, A.; Castilla, R.; Corela, Carlos; Crozon, J.; Davy, C.; D'acremont, E.; Droz, Laurence; Duarte, J. L.; Fernagu, P.; Ferrant, A.; Fischer, M.; Franke, D.; Inguane, H.; Jorry, Stephan; Jouet, G.; Loureiro, Afonso; Le Bouteiller, P.; Le Bihan, C.; Mahanjane, S.; Moocroft, D.; Pelleau, P.; Picot, M.; Pierre, D.; Pitel, M.; Rabineau, M.; Rombe, C.; Roudaut, M.; Senkans, A.; Toucanne, SamuelThe Natal Valley, offshore Mozambique, is a key area for understanding the evolution of East Gondwana. Within the scope of the integrated multidisciplinary PAMELA project, we present new wide-angle seismic data and interpretations, which considerably alter Geoscience paradigms. These data reveal the presence of a 30-km-thick crust that we argue to be of continental nature. This falsifies all the most recent palaeo-reconstructions of the Gondwana. This 30-km-thick continental crust 1,000 m below sea level implies a complex history with probable intrusions of mantle-derived melts in the lower crust, connected to several occurrences of magmatism, which seems to evidence the crucial role of the lower continental crust in passive margin genesis.
- The Portuguese national seismic network: products and servicesPublication . Carrilho, Fernando; Custodio, Susana; Bezzeghoud, Mourad; Oliveira, Carlos; Marreiros, Célia; Vales, Dina; Alves, Paulo; Pena, Areosa; Madureira, Guilherme; Escuer, Maria; Silveira, Graça; Corela, Carlos; Matias, Luis; Silva, Matilde; Veludo, Idalina; Dias, Nuno; Loureiro, Afonso; Borges, J. F.; Caldeira, Bento; Wachilala, Piedade; Fontiela, JoaoPortugal, located in the southwest region of the Eurasian plate, has been affected by several destructive earthquakes throughout its history, the most well-known being the 1755 Great Lisbon earthquake. The seismicity of the territory, both in the mainland and in the Azores and Madeira islands, has prompted the continuous development of seismic monitoring, from the first known macroseismic inquiry, following the 1755 Great Lisbon earthquake, to the current state-of-the-art seismic network. Once scattered in separate efforts, at present, most seismic stations in Portugal relay its data to a common data center, at Instituto Português do Mar e da Atmosfera, where data are automatically processed for the downstream generation of both manually revised and automatically generated products and services. In this article, we summarize the evolution of the permanent seismic network, its current status, the products and services that are publicly available, a recent effort of rapid deployment of a dense network following a mainshock, and state-of-the-art ocean-bottom seismometer developments.
- Lithospheric structuration onshore-offshore of the Sergipe-Alagoas passive margin, NE Brazil, based on wide-angle seismic dataPublication . Pinheiro, J. M.; Schnurle, P.; Evain, Mikael; Afilhado, Alexandra; Gallais, F.; Klingelhoefer, Frauke; Loureiro, Afonso; Fuck, R.; Soares, J.; Cupertino, J. A.; Viana, Adriano Roessler; Rabineau, Marina; Baltzer, A.; Benabdellouahed, M.; Dias, Nuno; Moulin, Maryline; Aslani, D.; Morvan, L.; Maze, J. P.; Pierre, D.; Roudaut-Pitel, M.; Rio, I.; Alves, D.; Barros, P.; Biari, Youssef; Corela, Carlos; Crozon, J.; Duarte, J. L.; Ducatel, C.; Falcão, C.; Fernagu, P.; Le Piver, D.; Mokeddem, Z.; Pelleau, P.; Rigoti, C.; Roest, W.; Roudaut, M.The structure and nature of the crust underlying the Camamu-Almada-Jequitinhonha-Sergipe-Alagoas basins System, in the NE Brazilian margin, were investigated based on the interpretation of 12 wide-angle seismic profiles acquired during the SALSA (Sergipe ALagoas Seismic Acquisition) experiment in 2014. In this work, we present two 220-km-long NW-SE combined wide-angle and reflection seismic profiles, SL 01 and SL 02, that have been acquired using 15 ocean-bottom-seismometers along each profile, offshore the southern part of the Sergipe Alagoas Basin (SAB), north of the Vaza-Barris Transfer zone. The SL 02 has a 150-km long inland continuation with 20 land-seismic-stations until the Sergipano Fold Belt (SFB). Wide-angle seismic forward modeling allows us to precisely divide the crust in three domains: beneath the continental shelf, a similar to 100 km wide necking zone is imaged where the continental crust thins from similar to 35 km on the Unthinned Continental Domain, which displays a three-layered crust structure, to less than 8 km on the Oceanic Crust Domain. In the necking zone, the upper and the middle layers thin dramatically and almost disappear, while the Moho discontinuity shows clear PmPs. The Continental-Oceanic Crust Boundary (COB) is located at similar to 80 km from the coastline and is marked by intracrustal seismic reflectors and changes in the seismic velocity, showing a sharp transition. On profile SL02, the oceanic crust is perturbed by a volcanic edifice together with an anomalous velocity zone underneath the area.