M5.5 Earthquake 77 km NE of ‘Ohonua, Tonga — July 6, 2025
2025-07-06 20:31:42 UTC (2025-07-06) · approx. 8:31 AM UTC-12 local
Maximum shaking intensity MMI 4.1 (moderate).
On July 6, 2025 at 20:31 UTC, a magnitude 5.5 shallow crustal earthquake struck 77 km NE of ‘Ohonua, Tonga, at a depth of 10.0 km and coordinates -20.9353°, -174.3501°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 72 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 465, placing it among routine seismic activity. The nearest populated place is `Ohonua (population 1,241).
Physical scale: An earthquake of magnitude 5.5 releases seismic energy equivalent to roughly 3 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 3.8 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Tonga, a region characterized by the Tonga-Kermadec subduction zone, where the Pacific Plate descends at up to 240 mm per year — the fastest plate convergence on Earth. The nearest mapped fault system is the Tonga Trench. View all earthquakes in Tonga.
Learn more: Magnitude scale · Aftershock sequences
Nearest Populated Places
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 15,390 |
| MMI 4 | light | 74,417 |
Earthquake Details
-174.3501°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.5 earthquake near ‘Ohonua, Tonga?
The magnitude 5.5 earthquake that struck 77 km NE of ‘Ohonua, Tonga on July 6, 2025 at 20:31 UTC had a depth of 10.0 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at -20.9353°, -174.3501°, which is 77 km NE of ‘Ohonua, Tonga. The nearest populated place is `Ohonua (population 1,241). View all earthquakes in Tonga.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.5 earthquakes can continue for days to weeks and gradually diminish over time.
Has Tonga had earthquakes this big before?
The largest recorded earthquake in Tonga was the M8.1 Tonga Trench earthquake of June 26, 1917. Today's magnitude 5.5 event is significantly smaller than that historical record.
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Location
Authoritative source: USGS event page (event ID: us7000qb20). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, July 6, 2025). M5.5 Earthquake 77 km NE of ‘Ohonua, Tonga — July 6, 2025. Retrieved September 12, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000qb20/