Reviewed by USGS51y ago
M4.6 earthquake south of Tonga
Thursday, October 16, 1975, 07:29:10 UTC · 24.639°S, 175.798°W
A magnitude 4.6 earthquake struck south of Tonga on Thursday, October 16, 1975, 07:29:10 UTC, at a depth of 30.0 km (shallow). It is the strongest earthquake within 300 km since an M5.4 on October 16, 1975.
- Magnitude
- 4.6
- Light · mb
- Depth
- 30 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
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
59 km
from the nearest mapped plate boundary, between the Kermadec and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
30 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 154 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8south of TongaOctober 11, 1975 · 74 km SE of this epicenter
- 7.6south of the Fiji IslandsDecember 18, 1963 · 106 km W of this epicenter
- 7.4south of TongaMarch 18, 1905 · 245 km E of this epicenter
- 7.3south of the Fiji IslandsJanuary 20, 1970 · 201 km SW of this epicenter
- 7.2south of the Fiji IslandsNovember 24, 1960 · 46 km W of this epicenter
- 7.0south of TongaJanuary 10, 1956 · 207 km S of this epicenter
- 6.8south of the Fiji IslandsJuly 4, 1963 · 290 km SW of this epicenter
- 6.7south of the Fiji IslandsSeptember 8, 1920 · 61 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1975M7.8
S Of Tonga
11 Oct 1975 · 74 km away
- 1963M7.5
Tonga Trench
18 Dec 1963 · 83 km away
tsunami
- 1956M7.0
Tonga Islands
10 Jan 1956 · 161 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.