vailulu'u is an active volcano, with earthquakes, volcanic eruptions and hydrothermal activity recorded. in particular, the seamount is a site with common earthquakes in this otherwise mostly aseismic part of the pacific plate and away from the earthquakes of the tonga trench, recording an average 4 earthquakes per day. seismic swarms were observed in 1973 and 1995; an earthquake swarm took place in 2000. the hypocentres of these earthquakes appear to coincide with the hydrothermal areas and the earthquakes correlate with the southeastern ridge, which is a rift zone.