Major M7.5 earthquake hits Tonga region

The epicenter was located 153 km (95 miles) W of Neiafu (population 4 320), 272 km (169 miles) N of Nuku‘alofa (population 22 400), Tonga, and 606 km (377 miles) ESE of Labasa (population 27 949), Fiji.

21 000 people are estimated to have felt moderate shaking, and 85 000 light.

Based on earthquake information and historic tsunami records, the earthquake is not expected to generate a tsunami, NWS PTWC said.

The USGS issued a Green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

Overall, the population in this region resides in structures that are highly vulnerable to earthquake shaking, though some resistant structures exist. The predominant vulnerable building types are unknown/miscellaneous types and wood construction.

Recent earthquakes in this area have caused secondary hazards such as tsunamis that might have contributed to losses.

Over the past 7 days, seismic activity in the Tonga region included a cluster of moderate to major earthquakes at both shallow and intermediate to deep depths.

The largest was today’s M7.5, followed by an M5.2 at 05:22 UTC, 157 km (98 miles) W of Neiafu, at a depth of 216 km (134 miles).

Earlier activity in the sequence included several shallower events near Hihifo, Tonga: M5.8 at 06:02 UTC on March 23, M5.9 at 22:26 UTC on March 22, M5.6 at 16:00 UTC on March 22, M6.3 at 15:30 UTC on March 22, and M6.2 events at 15:27 UTC on March 22, and at 06:15 UTC on March 22, both at 10 km (6.2 miles) depth.

Today’s M7.5 earthquake occurred within the Tonga segment of the Kermadec-Tonga subduction zone, one of the most seismically active plate boundaries in the world.

In this region, the Pacific Plate subducts westward beneath the Australia Plate along the Tonga Trench. Convergence rates increase northward from about 60 mm/year (2.4 inches/year) at the southern Kermadec Trench to about 90 mm/year (3.5 inches/year) at the northern Tonga Trench, while strong back-arc extension and slab rollback increase the overall subduction velocity along the Tonga Trench to about 150 to 240 mm/year (5.9 to 9.4 inches/year). This makes the Tonga margin one of the fastest subduction systems globally.

Large earthquakes in this system occur on the plate interface, within the descending Pacific Plate, within the overriding plate, and less commonly east of the trench in the outer rise. Given the depth of this March 24 event, it most likely occurred within the subducting Pacific slab rather than on the shallow plate boundary itself.

Deep earthquakes are common in the Tonga region because the slab descends rapidly into the mantle and remains capable of brittle failure at great depth.

The Kermadec-Tonga margin has produced numerous major earthquakes. Since 1900, about 40 earthquakes of M7.5 or greater have been recorded in the system, most north of 30°S. One of the most significant was the September 29, 2009, M8.1 outer-rise earthquake south of Samoa, about 40 km (25 miles) east of the Tonga Trench, which generated a tsunami that killed at least 180 people.

Estimated population exposure to earthquake shaking

Selected cities exposed

Regional seismicity

References:

¹ M7.5 earthquake Tonga – USGS – March 24, 2026

² M7.6 earthquake Tonga – EMSC – March 24, 2026

³ M7.6 earthquake Tonga – PTWC – March 24, 2026

Rishav Kothari

I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.

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