Reviewed by USGS51y ago
M5.4 earthquake south of Tonga
Wednesday, October 15, 1975, 17:24:32 UTC · 24.746°S, 175.180°W
A magnitude 5.4 earthquake struck south of Tonga on Wednesday, October 15, 1975, 17:24:32 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.5 on October 13, 1975.
- Magnitude
- 5.4
- Moderate · 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 earthquakeDashed circle: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
2 kilotons of TNT
That is about 1/8 of the Hiroshima bomb. It released about 4 times the energy of a magnitude 5.0.
Tectonic setting
5 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
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 75 km
USGS lists 2 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.4 on October 16, 1975. 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 143 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 · 18 km S of this epicenter
- 7.6south of the Fiji IslandsDecember 18, 1963 · 168 km W of this epicenter
- 7.4south of TongaMarch 18, 1905 · 185 km E of this epicenter
- 7.3south of the Fiji IslandsJanuary 20, 1970 · 243 km SW of this epicenter
- 7.2south of the Fiji IslandsNovember 24, 1960 · 108 km W of this epicenter
- 7.0south of TongaJanuary 10, 1956 · 187 km S of this epicenter
- 6.8south of TongaApril 19, 1905 · 270 km SE of this epicenter
- 6.7south of the Fiji IslandsSeptember 8, 1920 · 124 km W 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 · 18 km away
- 1963M7.5
Tonga Trench
18 Dec 1963 · 143 km away
tsunami
- 1956M7.0
Tonga Islands
10 Jan 1956 · 140 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.