Slow deformation event between large intraslab earthquakes at the Tonga Trench inferred from geodetic and seismological data

Slow deformations associated with a subducting slab can affect quasi-static displacements and seismicity over a wide range of depths. Here, we analyse the seismotectonic activities at the Tonga-Trench subduction zone, which is the world’s most active area with regard to deep earthquakes, using data from GNSS and an earthquake catalogue. We find that trenchward transient displacements and quiescence of deep earthquakes, in terms of background seismicity, were bounded in time by large intraslab earthquakes in 2009 and 2013. We call this event as "slow deformation event”. It may have been triggered by a distant and shallow M8.1 earthquake, which implies a slow slip event at the plate interface or a temporal acceleration of the subduction of the Pacific Plate.