Earthquakes in Tonga — September 2025

13 earthquakes were recorded in Tonga during September 2025, an average of 0.4 per day.

13 reached magnitude 4 or above and 5 reached magnitude 5 or above. The average focal depth was 180 km.

The month's largest event in Tonga was a magnitude 5.1 earthquake near ‘Ohonua, Tonga on 30 September 2025 at 17:50 UTC. A magnitude 5.1 earthquake radiates roughly 674 tons of TNT equivalent in seismic energy.

That is below the Tonga monthly average of 18 events over the period we cover — a comparatively quiet month, and down from the 17 recorded the previous month.

46% of events here are shallow (under 70 km), 31% intermediate (70–300 km) and 23% deep-focus (over 300 km). That proportion of deep-focus events is the signature of a subduction zone: only a cold slab descending into the mantle stays brittle enough to rupture at those depths.

By band, the catalogue holds 8 in the magnitude 4 range, 5 in the magnitude 5 range.

Activity peaked on 26 September, when 3 events were recorded.

The month's largest events were M5.1 near ‘Ohonua, Tonga on 30 September at 10 km; M5.1 near Hihifo, Tonga on 26 September at 10 km; M5.0 near ‘Ohonua, Tonga on 03 September at 45 km.

That is 30% below the 18 events Tonga averages per month across the 21 months on record.