Slow deformation event following large intraslab earthquake at the Tonga subduction zone

Abstract:

Aseismic slab deformation or fluid movement may trigger earthquakes at plate subduction zones over a wide range of depths. In the present study, we analyze seismotectonic activities in the Tonga subduction zone, which is the most active location regarding deep earthquakes in the world, based on geophysical data from a global navigation satellite system and an earthquake catalog. Quiescence of deep earthquakes in terms of background seismicity and trench-ward surface displacements were approximately coexistent, forming an event series with three large intraslab earthquakes in 2009 and 2013. The trench-ward movement may have been triggered by a shallow M8.1 earthquake, which implied a slow deformation event, namely a slow-slip event at the plate interface or temporal acceleration of the subduction of the Pacific Plate. These findings provide new insights into slow earthquake observations and the linkage between shallow and deep earthquakes in the subduction zone.