Understanding the Present-day Tectonics of the Azores Archipelago using Geodetic Observations

Abstract:

The Azores Archipelago was created by the temporal evolution of the Triple Junction between three major tectonic plates: Eurasia, Nubia and North America. The North American plate diverges from the Eurasian and Nubian plates on the well defined Mid Atlantic Ridge. But, the spatial and temporal evolutions of the boundary between the Eurasian and Nubian plates, which is characterized by a transtensive regime along the Azores block, has been much more difficult to understand despite the large number of studies carried out up to the present using single and multidisciplinary approaches.

In this work, we update and investigate the present-day velocity field using the network of CORS (Continuously Operating Reference Stations) GNSS stations being installed in the Archipelago since 2001. The number of stations and the timespan permits now to better constrain the present-day velocity field of Azores derived from GNSS data, previously mainly based on campaign stations.

We investigate the location of the Triple Junction in the Azores using this derived regional GNSS velocity field. We focus principally on the current vertical field. Most stations in this area show subsidence of approximately 1.2 mm/yr. This is in agreement with lithospheric cooling. Nevertheless, recent studies have demonstrated Santa Maria Island is rising, differing from this global picture. Using GNSS data we try to understand the processes that constrain subsidence and uplift in the Azores. In addition, we combine the GNSS solutions with satellite data from GRACE to evaluate the value of these data to refine the velocity field for the entire Archipelago.

This work uses resources provided by C4G – Collaboratory for Geosciences (POCI-01-0145-FEDER-022151) and FCT/UIDB/50019/2020 – IDL, both funded by FCT.