EarthBrowserEarthquake · Sunday, October 18, 2026
Magnitude 4.3 earthquake 236 km WSW of Houma, Tonga
A magnitude 4.3 (light) earthquake struck 236 km WSW of Houma, Tonga on Sunday, October 18, 2026 at , at a depth of 279 km (intermediate).
- Magnitude
- 4.3Light
- Depth
- 279km · intermediate
- Time
- Epicenter
- 21.64° S
177.53° W - Aftershocks so far
- 8within 250 km
- Largest aftershock
- 6.1M
23 days ago · USGS id us6000u36h · last revised
The full globe opens the 3D cross-section: the hypocenter at depth, the plate boundary and subducting slab where there is one, the aftershock sequence as it grows, and the sea floor around an offshore epicenter.
What a magnitude 4.3 means
Light earthquakes are widely felt near the epicenter, rattling windows and shelves, but rarely cause damage.
A magnitude 4.3 releases about 32 times the seismic energy of a magnitude 3.3, roughly the energy of 43 tonnes of TNT. Magnitude measures the energy released at the source; how hard the ground shook at any one place depends on distance, depth and local geology, and is reported separately as intensity.
Intermediate-depth earthquakes (70 to 300 km) occur inside subducting slabs. The extra distance to the surface spreads the shaking over a wider area at lower intensity.
Nearby earthquakes and aftershocks
This event is part of a sequence: a larger magnitude 6.1 struck 132 km away on Nov 5, 17:21 UTC, so this is most likely one of its foreshocks.
| Time (UTC) | Magnitude | Depth | Distance | Location |
|---|---|---|---|---|
| 4.5 | 572 km | 152 km | Fiji region | |
| 6.1 | 535 km | 132 km | Fiji region | |
| 4.3 | 463 km | 101 km | 289 km W of Houma, Tonga | |
| 4.7 | 35 km | 231 km | 165 km SSW of ‘Ohonua, Tonga | |
| 4.2 | 625 km | 179 km | Fiji region | |
| 4.0 | 567 km | 239 km | Fiji region | |
| 4.1 | 535 km | 166 km | 268 km WNW of Houma, Tonga | |
| 4.4 | 559 km | 143 km | Fiji region | |
| before | 4.2 | 586 km | 211 km | south of the Fiji Islands |
| before | 4.4 | 594 km | 227 km | south of the Fiji Islands |
| before | 5.9 | 585 km | 155 km | Fiji region |
| before | 4.4 | 597 km | 219 km | south of the Fiji Islands |
| before | 4.6 | 513 km | 140 km | 260 km WNW of Houma, Tonga |
| before | 4.6 | 560 km | 189 km | 268 km WNW of Houma, Tonga |
| before | 4.4 | 638 km | 196 km | Fiji region |
| before | 4.7 | 573 km | 146 km | Fiji region |
| before | 4.8 | 122 km | 226 km | 26 km NW of Houma, Tonga |
| before | 4.4 | 507 km | 151 km | 276 km WNW of Houma, Tonga |
Frequently asked questions
How is earthquake magnitude measured?
Modern magnitudes are moment magnitudes (Mw), computed from the seismic moment: the area of the fault that slipped, how far it slipped and the rigidity of the rock. Each whole step up the scale is about 32 times more energy, so a magnitude 7 releases roughly a thousand times the energy of a magnitude 5.
What is the difference between magnitude and intensity?
Magnitude is one number for the whole earthquake, describing the energy released at the source. Intensity describes the shaking at a particular place, on the Modified Mercalli scale from I (not felt) to X+ (extreme), and falls off with distance from the epicenter.
What is an aftershock?
An aftershock is a smaller earthquake in the same area after a larger one, as the crust around the ruptured fault adjusts to the new stresses. They are most frequent in the first hours and days and fade over weeks to months, though a large mainshock can produce aftershocks for years.
Why do the magnitude and location change?
The first solution uses the nearest stations only. As recordings arrive from more seismographs around the world, USGS revises the magnitude, depth and epicenter, sometimes several times in the first hours. This page reflects the latest revision.
Where does this earthquake data come from?
From the U.S. Geological Survey’s real-time earthquake feeds, which combine the USGS National Earthquake Information Center with regional seismic networks worldwide. EarthBrowser ingests the feed every minute.