A Quiet but Deep Trouble in Tonga Subduction Zone

The Tonga subduction zone marks the convergent plate boundary between the Pacific and Australian plates, and it produces more large-magnitude deep earthquakes (depth >300 km) than anywhere else in the world. Deep earthquakes constitute less than 1% of the total earthquakes (M > 6) of the world and among them, ~66% are hosted by the Tonga subduction zone alone. On 19 August 2018, it produced globally the second largest deep earthquake (Mw 8.2, depth ~580 km) in the instrumentally recorded history of earthquakes. The 24 May 2013 Okhotsk earthquake with Mw 8.3 still holds the record for being the largest magnitude deep earthquake.