An earthquake of about magnitude 5 struck the South Pacific south of Tonga at 14:56 UTC on August 4, 2026. Nobody reported feeling it.
The U.S. Geological Survey, first to publish the quake, put the epicenter at 24.5996°S, 175.3870°W. Its reviewed record lists a magnitude of 5.0 and a depth of 10 km, and carries no tsunami flag. Early figures were slightly higher. The first USGS reading was 5.1, and the European-Mediterranean Seismological Centre also logged 5.1, at 12 km. Geoscience Australia put it at 5.0 and Germany’s GFZ at 5.11, though GFZ placed the epicenter south of Fiji.
How deep, and how far from people
Depth is the shaky number. A 10 km figure in a quake catalog often means the instruments could not pin the depth down, and the USGS record marks it as operator assigned. The agencies’ own answers ranged from 10 km to 149 km. Think of it like judging how far away lightning is from the thunder alone: you get a rough range, not a measurement. Depth matters because the same magnitude shakes the ground harder when the rupture sits closer to the surface.
Distance helped here. VolcanoDiscovery, which compiles the agencies’ data, placed the epicenter 352 km (219 mi) from Tonga, about 360 km south of ‘Eua Island. In Nuku’alofa, the capital, 386 km (240 mi) away, shaking was probably very weak. Ha’atu’a, a town of 489 people, sits 360 km north of the epicenter and would have felt about the same. The site’s page showed zero felt reports and no recorded aftershocks.
A busy patch of ocean
This part of the Pacific is used to it. Within 100 km of the epicenter, VolcanoDiscovery counts about 28.1 quakes a year on average, based on 26 years of data and an archive back to 1900, including 4.4 of magnitude 5 or higher. A magnitude 6 or larger turns up roughly once every 11.5 years there, and at least 11 have struck since 1900.
Sources
- USGS earthquake event record us6000ti0r (official dataset, USGS Earthquake Hazards Program)
- Strong Mag. 5.1 Earthquake – South of Tonga on Tuesday, Aug 4, 2026 | VolcanoDiscovery (quake record compiling agency data)
