C. Corela

Deep structure of the Santos basin-São Paulo plateau system, SE Brazil

The structure and nature of the crust underlying the Santos Basin-Sao Paulo Plateau System (SSPS), in the SE Brazilian margin, are discussed based on five wide-angle seismic profiles acquired during the Santos Basin (SanBa) experiment in 2011. Velocity models allow us to precisely divide the SSPS in six domains from unthinned continental crust (Domain CC) to normal oceanic crust (Domain OC). A seventh domain (Domain D), a triangular shape region in the SE of the SSPS, is discussed by Klingelhoefer et al. (2014). Beneath the continental shelf, a ~100 km wide necking zone (Domain N) is imaged where the continental crust thins abruptly from ~40 km to less than 15 km. Toward the ocean, most of the SSPS (Domains A and C) shows velocity ranges, velocity gradients, and a Moho interface characteristic of the thinned continental crust. The central domain (Domain B) has, however, a very heterogeneous structure. While its southwestern part still exhibits extremely thinned (7 km) continental crust, its northeastern part depicts a 2–4 km thick upper layer (6.0–6.5 km/s) overlying an anomalous velocity layer (7.0–7.8 km/s) and no evidence of a Moho interface. This structure is interpreted as atypical oceanic crust, exhumed lower crust, or upper continental crust intruded by mafic material, overlying either altered mantle in the first two cases or intruded lower continental crust in the last case. The deep structure and v-shaped segmentation of the SSPS confirm that an initial episode of rifting occurred there obliquely to the general opening direction of the South Atlantic Central Segment.

Progresses in the Assessment of Tsunami Genesis and Impacts around the Portuguese Coasts

The tsunami generated by the 1755.11.01 earthquake, as reported by coeval sources, was the major event of its kind in the North Atlantic, until nowadays. The coasts of the Iberian Peninsula and Northwest Morocco were deeply affected by that phenomenon, with tremendous impacts on the city of Lisbon. For the last 20 years, significant support was received from EU (Projects DETWS, IAM, GITEC, GITEC-TWO and BIGSETS), national projects (MATESPRO, RIFANO and RIMAR) and bi-lateral cooperation (HITS, TTR-10, SISMAR and VOLTAIRE). This allowed significant improvements on the knowledge of parameters sources and tsunami propagation. Tsunami propagation models were developed, being the simulations controlled by real data, deducted from historical reports or instrumental networks. In order to assess the considerable impacts along the Portuguese coasts, different run-up models have been used and tested. To evaluate the tsunami hazard, comprehensive studies were developed, recognizing the importance of the inter-disciplinary approach, including the study of induced continental sedimentary deposits. The location of the 1755.11.01 source has been a key question, motivating intensive marine research in the southern area of Portugal, looking for unquestionable morphological or geological evidence of fault rupture and the present-day seismic activity.