Publication
The South-West Iberia rifted margin: lithospheric structure, geodynamic processes and seismic hazard
| Summary: | The lithospheric structure of the Southwest Iberian margin was investigated along an active seismic profile southwest of São Vicente Cape, extending for about 320 km, from the southern Tagus Abyssal Plain to the westernmost extension of the Gulf of Cadiz. From northeast to southwest, this profile intersects almost perpendicularly three major thrust faults: the Tagus Abyssal Plain, Marquês de Pombal and Horseshoe faults. The crustal structure, derived from spatially coincident wide-angle seismics (WAS) and multichannel seismic (MCS) data, was validated and constrained using gravimetric data. Joint travel-time inversion of refracted phases identified in WAS and reflected seismic phases from both WAS and MCS records produced a detailed two-dimensional P-wave velocity (Vp) structure. The resulting model reveals a Vp distribution with abrupt lateral velocity and structural variations, characterized by a rugged basement top and sharp changes in crustal thickness. Three main lithospheric domains were identified the model, with continental, oceanic and mantle (exhumed mantle) affinities. The inversion of deeper secondary seismic phases from the WAS data revealed the presence of four major southeast-dipping reflectors extending down to approximately 20 km depth. Three of these reflectors show strong correlation with the regional faults intersected by the seismic profile and allow for a more detailed characterization of their geometry at depth, contributing to an improved assessment of the seismic and tsunamigenic potential in the area. Integrating the modelled and interpreted seismic results with the locations of recent well-constrained earthquake hypocenters suggests that the Tagus Abyssal Plain fault and especially Marquês de Pombal fault may extend deeper levels than previously thought. |
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| Main Authors: | Correia, Ricardo |
| Subject: | Southwest iberian margin Lithospheric structure Tectonic setting Wide-angle seismics Multichannel seismics Seismic tomography |
| Year: | 2025 |
| Country: | Portugal |
| Document type: | doctoral thesis |
| Access type: | open access |
| Associated institution: | Universidade de Aveiro |
| Language: | English |
| Origin: | RIA - Repositório Institucional da Universidade de Aveiro |
| Summary: | The lithospheric structure of the Southwest Iberian margin was investigated along an active seismic profile southwest of São Vicente Cape, extending for about 320 km, from the southern Tagus Abyssal Plain to the westernmost extension of the Gulf of Cadiz. From northeast to southwest, this profile intersects almost perpendicularly three major thrust faults: the Tagus Abyssal Plain, Marquês de Pombal and Horseshoe faults. The crustal structure, derived from spatially coincident wide-angle seismics (WAS) and multichannel seismic (MCS) data, was validated and constrained using gravimetric data. Joint travel-time inversion of refracted phases identified in WAS and reflected seismic phases from both WAS and MCS records produced a detailed two-dimensional P-wave velocity (Vp) structure. The resulting model reveals a Vp distribution with abrupt lateral velocity and structural variations, characterized by a rugged basement top and sharp changes in crustal thickness. Three main lithospheric domains were identified the model, with continental, oceanic and mantle (exhumed mantle) affinities. The inversion of deeper secondary seismic phases from the WAS data revealed the presence of four major southeast-dipping reflectors extending down to approximately 20 km depth. Three of these reflectors show strong correlation with the regional faults intersected by the seismic profile and allow for a more detailed characterization of their geometry at depth, contributing to an improved assessment of the seismic and tsunamigenic potential in the area. Integrating the modelled and interpreted seismic results with the locations of recent well-constrained earthquake hypocenters suggests that the Tagus Abyssal Plain fault and especially Marquês de Pombal fault may extend deeper levels than previously thought. |
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