Ongoing tectonic subsidence in the Lesser Antilles subduction zone

Abstract

Summary Geological estimates of vertical motions in the central part of the Lesser Antilles show subsidence on timescales ranging from 125.000 to 100 years, which has been interpreted to be caused by interseismic locking along the subduction megathrust. However, horizontal GNSS velocities show that the Lesser Antilles subduction interface is currently building up little to no elastic strain. Here we present new present-day vertical velocities for the Lesser Antilles islands and explore the link between short- and long-term vertical motions and their underlying processes. We find a geodetic subsidence of the Lesser Antilles island arc at 1-2 mm/yr, consistent with the ∼100-year trend derived from coral micro-atolls. Using elastic dislocation models, we show that a locked or partially-locked subduction interface would produce uplift of the island arc, opposite to the observations, hence supporting a poorly-coupled subduction. We propose that this long-term, margin-wide subsidence is controlled by slab dynamic processes, such as slab rollback. Such processes could also be responsible for the aseismic character of the subduction megathrust.

Hurricane Irma: an unprecedented event over the last 3700 years? Geomorphological changes and sedimentological record in Codrington Lagoon, Barbuda

“…Microatolls studies along the eastern coasts of the island (Hog Hole) revealed that this island subsided as a response of interseismic strain accumulation over more than five decades at rate of about 5mm/yr. The sign of those vertical deformations is compatible, with that of the vertical 575 deformation estimated with a GNSS station located few kilometers away to the west, but larger by an order of size (0.5 mm/year +/-1 for a time period between 1994, van Rijsingen et al, 2022. In this area, Weil-Accardo et al (2022) studied a set of quaternary reef terraces and showed that the eastern part of Barbuda has undergone a long-term uplift of 0,05 to 0.1 mm/year over the last 330 Ka.…”

Thermally-constrained fluid circulation and seismicity in the Lesser Antilles subduction zone

“…However, investigations on some coral micro-atolls suggest that vertical deformation are possibly related to a local increase in interseismic coupling at great depth (Philibosian et al, 2022). A more recent study (van Rijsingen et al, 2022) has however, presented vertical velocities for the Lesser Antilles Islands and examine the link between the short and long-term vertical motions and their underlying processes. Based on their elastic dislocation models, they show that a locked or partially locked interplate up to 60 km depth would produce uplift of the island arcs, which is opposite to the observations of microatolls and GNSS data.…”

Modeled Flooding by Tsunamis and a Storm Versus Observed Extent of Coral Erratics on Anegada, British Virgin Islands—Further Evidence for a Great Caribbean Earthquake Six Centuries Ago

“…Far to the southeast, along the Lesser Antilles Subduction Zone, an 1843 earthquake of estimated magnitude M7.8–M8.5 produced hardly any tsunami (Bernard & Lambert, 1988). The megathrust earthquake potential in this area was recently debated (Philibosian et al., 2022; van Rijsingen et al., 2022).…”