Reviewed by USGSTonga3y ago
M5.5 earthquake 65 km NW of Hihifo, Tonga
Tuesday, October 10, 2023, 07:21:30 UTC · 15.532°S, 174.223°W
A magnitude 5.5 earthquake struck 65 km NW of Hihifo, Tonga on Tuesday, October 10, 2023, 07:21:30 UTC, at a depth of 10.0 km (shallow). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M6.1 on August 8, 2023.
- Magnitude
- 5.5
- Moderate · mww
- Depth
- 10 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- IV
- Light (ShakeMap)
- PAGER alert
- Green
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 75 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
3 kilotons of TNT
That is about 1/6 of the Hiroshima bomb. It released about 6 times the energy of a magnitude 5.0.
Tectonic setting
25 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
10 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
Modelled from the ShakeMap and population data. Alert level green: low likelihood of casualties and damage.
- II · Weak shaking
- 6,100 people
Estimated shaking in nearby towns
- HihifocapitalPopulation 815IV · Light
- GataivaiPopulation 1,100II · Weak
After the main event
Aftershocks within 75 km
USGS lists 3 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M4.6 on October 28, 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 1,935 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 · 228 km E of this epicenter
- 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 118 km NE of this epicenter
- 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 205 km SE of this epicenter
- 7.7133 km NE of Hihifo, TongaSeptember 1, 1981 · 138 km NE of this epicenter
- 7.682 km WNW of Hihifo, TongaMay 10, 2023 · 31 km W of this epicenter
- 7.6199 km ESE of Hihifo, TongaApril 2, 1977 · 262 km SE of this epicenter
- 7.488 km NNE of Hihifo, TongaApril 7, 1995 · 83 km NE of this epicenter
- 7.2117 km SSW of Hihifo, TongaJanuary 8, 2000 · 155 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 · 228 km away
192 deaths$285 million damagetsunami
- 1917M8.3
Samoa Islands
26 Jun 1917 · 131 km away
2 deathsModerate damage ($1–5M)tsunami
- 1981M7.7
Apia; American Samoa: Pago Pago
1 Sep 1981 · 138 km away · intensity VI
Limited damage (under $1M)tsunami
- 1977M7.6
Apia
2 Apr 1977 · 262 km away · intensity VI
Limited damage (under $1M)tsunami
- 1975M7.8
Samoa Islands
26 Dec 1975 · 205 km away · intensity V
tsunami
- 2023M7.6
Hihifo
10 May 2023 · 42 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.