Reviewed by USGSTonga45y ago
M4.9 earthquake 113 km SSE of Hihifo, Tonga
Sunday, October 25, 1981, 06:25:27 UTC · 16.948°S, 173.544°W
A magnitude 4.9 earthquake struck 113 km SSE of Hihifo, Tonga on Sunday, October 25, 1981, 06:25:27 UTC, at a depth of 40.0 km (shallow). It is the strongest earthquake within 300 km since an M5.0 on October 24, 1981.
- Magnitude
- 4.9
- Light · mb
- Depth
- 40 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 earthquake
In context
How big was it, and why here?
Energy released
338 tons of TNT
That is about 1/45 of the Hiroshima bomb. A magnitude 5.0 releases about 1 times more energy.
Tectonic setting
104 km
from the nearest mapped plate boundary, between the Tonga and Niuafo'ou plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
40 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 580 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.11919 Tonga EarthquakeApril 30, 1919 · 192 km SE of this epicenter
- 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 219 km N of this epicenter
- 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 138 km NE of this epicenter
- 7.7133 km NE of Hihifo, TongaSeptember 1, 1981 · 226 km N of this epicenter
- 7.6199 km ESE of Hihifo, TongaApril 2, 1977 · 157 km E of this epicenter
- 7.4103 km ESE of Neiafu, TongaFebruary 27, 1921 · 224 km S of this epicenter
- 7.385 km ESE of Neiafu, TongaJanuary 2, 1907 · 237 km S of this epicenter
- 7.2108 km SE of Neiafu, TongaDecember 19, 1906 · 257 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:
- 1917M8.3
Samoa Islands
26 Jun 1917 · 171 km away
2 deathsModerate damage ($1–5M)tsunami
- 1919M8.1
Tonga Islands
30 Apr 1919 · 190 km away
Limited damage (under $1M)tsunami
- 1865M8.0
Tonga Islands
18 Nov 1865 · 284 km away
Limited damage (under $1M)tsunami
- 1981M7.7
Apia; American Samoa: Pago Pago
1 Sep 1981 · 226 km away · intensity VI
Limited damage (under $1M)tsunami
- 1977M7.6
Apia
2 Apr 1977 · 157 km away · intensity VI
Limited damage (under $1M)tsunami
- 1975M7.8
Samoa Islands
26 Dec 1975 · 138 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.