Reviewed by USGSTonga51y ago
M4.2 earthquake 186 km ESE of Hihifo, Tonga
Thursday, March 11, 1976, 18:32:16 UTC · 16.436°S, 172.122°W
A magnitude 4.2 earthquake struck 186 km ESE of Hihifo, Tonga on Thursday, March 11, 1976, 18:32:16 UTC, at a depth of 33.0 km (shallow).
- Magnitude
- 4.2
- Light · mb
- Depth
- 33 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
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
20 km
from the nearest mapped plate boundary, between the Tonga and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
33 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 274 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 · 212 km S of this epicenter
- 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 202 km NW of this epicenter
- 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 41 km NW of this epicenter
- 7.4103 km ESE of Neiafu, TongaFebruary 27, 1921 · 291 km S of this epicenter
- 7.1112 km NNE of Hihifo, TongaApril 14, 1957 · 207 km NW of this epicenter
- 6.9127 km S of Hihifo, TongaMay 8, 1913 · 211 km W of this epicenter
- 6.8100 km SE of Hihifo, TongaDecember 20, 1914 · 116 km W of this epicenter
- 6.7127 km NE of Neiafu, TongaNovember 27, 1949 · 188 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 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 · 140 km away
2 deathsModerate damage ($1–5M)tsunami
- 1919M8.1
Tonga Islands
30 Apr 1919 · 217 km away
Limited damage (under $1M)tsunami
- 1975M7.8
Samoa Islands
26 Dec 1975 · 41 km away · intensity V
tsunami
- 1957M7.5
Samoa Islands
14 Apr 1957 · 140 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.