M6.1 Earthquake 105 km NE of Hihifo, Tonga — August 8, 2023
2023-08-08 18:38:54 UTC (2023-08-08) · approx. 6:38 AM UTC-12 local
Felt by 16 people across nearby locations. Maximum shaking intensity MMI 4.1 (moderate).
On August 8, 2023 at 18:38 UTC, a magnitude 6.1 shallow crustal earthquake struck 105 km NE of Hihifo, Tonga, at a depth of 42.0 km and coordinates -15.2082°, -173.1883°. The earthquake was reported felt by 16 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 4.1 (moderate). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 208 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 578, placing it among routine seismic activity. The nearest populated place is Hihifo (population 815).
Physical scale: An earthquake of magnitude 6.1 releases seismic energy equivalent to roughly 21 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 9.7 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
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 16 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
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 | 153,524 |
| MMI 4 | light | 55,020 |
Earthquake Details
-173.1883°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 6.1 earthquake near Hihifo, Tonga?
The magnitude 6.1 earthquake that struck 105 km NE of Hihifo, Tonga on August 8, 2023 at 18:38 UTC had a depth of 42.0 km. It was felt by 16 people with maximum shaking intensity of MMI 4.1 (moderate). For context, this was a strong earthquake capable of causing significant damage.
Where did the earthquake occur?
The earthquake epicenter was located at -15.2082°, -173.1883°, which is 105 km NE of Hihifo, Tonga. The nearest populated place is Hihifo (population 815). View all earthquakes in Tonga.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 6.1 earthquakes can continue for weeks to months 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 6.1 event is significantly smaller than that historical record.
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Location
Authoritative source: USGS event page (event ID: us6000kyph). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, August 8, 2023). M6.1 Earthquake 105 km NE of Hihifo, Tonga — August 8, 2023. Retrieved October 17, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kyph/