GPS and tectonic evidence for a diffuse plate boundary at the Azores Triple Junction

Constraints on the structure of the crust and lithosphere beneath the Azores Islands from teleseismic receiver functions

“…The islands São Miguel and Santa Maria lie on the oldest lithosphere of the Azores Plateau, which could be a factor for accumulation of an underplated layer. Moreover, Santa Maria is the oldest island of the Azores and is located at the southern edge of the 140 km wide shear zone of oblique extensional deformation associated with a diffuse plate boundary, being largely unaffected by active tectonics when compared to the other islands of the Eastern and Central groups (Hipolito et al 2013;Marques et al 2013). Underplating beneath the Canary Islands and Cape Verde shows a loose correlation with age, that is, older islands are more likely to exhibit evidence of underplating (Lodge & Helffrich 2006;Lodge et al 2012).…”

“…1). Whilst the Western Group is located to the west of the MAR, the remaining islands straddle the diffuse plate boundary between the Eurasian and Nubian plates (Madeira & Ribeiro 1990;Luis et al 1994;Marques et al 2013).…”

Correlated Changes Between Volcanic Structures and Magma Composition in the Faial Volcanic System, Azores

“…The subparallel lineaments have previously been interpreted to be extinct rift axes related to the movement of the recently active Terceira Rift. Rift-related structural features on Faial imply that rifting has played a role in the past (Luis et al, 1994;Miranda et al, 1998;Gente et al, 2003) and recent observations of earthquake epicenters suggest that tectonic movements still occur (Fernandes et al, 2002;Dias et al, 2007;Matias et al, 2007;Marques et al, 2013). The extension combined with volcanic activity during the past 1 Ma (Madeira et al, 1995;Hildenbrand et al, 2012;Beier et al, 2015) and the most recent Capelinhos eruption in 1957-1958 provides an opportunity to investigate the interaction between magmatic and tectonic processes in time and space.…”

Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

“…Most of the identified faults in the Azores archipelago are considered active (Madeira, 1998;Madeira and Brum da Silveira, 2003;Marques et al, 2013;Madeira et al, 2015) and the major faults usually have well-developed scarps; however the volcanic nature of the islands, together with differential erosion, can attenuate or amplify the tectonic slope (Madeira and Brum da Silveira, 2003) and even make the identification of tectonic structures difficult (due to scarp burial by pumice deposits, for instance). In addition, the exuberant vegetation of some of the Azorean islands covers most of the geological structures.…”