Reviewed by USGSTonga2y ago
M4.2 earthquake 80 km NNW of Hihifo, Tonga
Wednesday, October 18, 2023, 21:30:20 UTC · 15.248°S, 173.957°W
A magnitude 4.2 earthquake struck 80 km NNW of Hihifo, Tonga on Wednesday, October 18, 2023, 21:30:20 UTC, at a depth of 61.1 km (shallow).
- Magnitude
- 4.2
- Light · mb
- Depth
- 61 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
30 tons of TNT
That is about 1/500 of the Hiroshima bomb. A magnitude 5.0 releases about 16 times more energy.
Tectonic setting
28 km
from the nearest mapped plate boundary, between the Tonga and Niuafo'ou plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
61 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.3 on October 19, 2023. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,826 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.12009 Samoa EarthquakeSeptember 29, 2009 · 201 km E of this epicenter
- 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 79 km E of this epicenter
- 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 195 km SE of this epicenter
- 7.7133 km NE of Hihifo, TongaSeptember 1, 1981 · 99 km E of this epicenter
- 7.682 km WNW of Hihifo, TongaMay 10, 2023 · 71 km SW of this epicenter
- 7.6199 km ESE of Hihifo, TongaApril 2, 1977 · 256 km SE of this epicenter
- 7.488 km NNE of Hihifo, TongaApril 7, 1995 · 46 km E of this epicenter
- 7.2117 km SSW of Hihifo, TongaJanuary 8, 2000 · 189 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 194 recorded deaths. The most severe:
- 2009M8.1
Samoa Islands
29 Sep 2009 · 201 km away
192 deaths$285 million damagetsunami
- 1917M8.3
Samoa Islands
26 Jun 1917 · 106 km away
2 deathsModerate damage ($1–5M)tsunami
- 1981M7.7
Apia; American Samoa: Pago Pago
1 Sep 1981 · 99 km away · intensity VI
Limited damage (under $1M)tsunami
- 1977M7.6
Apia
2 Apr 1977 · 256 km away · intensity VI
Limited damage (under $1M)tsunami
- 1975M7.8
Samoa Islands
26 Dec 1975 · 196 km away · intensity V
tsunami
- 2023M7.6
Hihifo
10 May 2023 · 80 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.