Reviewed by USGSTonga70y ago
M6.3 earthquake 123 km SSW of ‘Ohonua, Tonga
Sunday, November 4, 1956, 07:05:49 UTC · 22.326°S, 175.486°W
A magnitude 6.3 earthquake struck 123 km SSW of ‘Ohonua, Tonga on Sunday, November 4, 1956, 07:05:49 UTC, at a depth of 48.7 km (shallow). It is the strongest earthquake within 300 km since an M6.7 on August 6, 1955.
- Magnitude
- 6.3
- Strong · mw
- Depth
- 49 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
38 kilotons of TNT
That is about 3 times the Hiroshima bomb. It released about 80 times the energy of a magnitude 5.0.
Tectonic setting
118 km
from the nearest mapped plate boundary, between the Tonga and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
49 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 100 km
USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 59 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.0TongaJanuary 4, 1903 · 264 km N of this epicenter
- 7.8159 km W of Pangai, TongaDecember 14, 1950 · 294 km N of this epicenter
- 7.8111 km SSE of Pangai, TongaJune 26, 1913 · 252 km NE of this epicenter
- 7.5110 km E of ‘Ohonua, TongaSeptember 8, 1948 · 205 km NE of this epicenter
- 7.3227 km WNW of Haveluloto, TongaApril 16, 1937 · 270 km NW of this epicenter
- 6.915 km WSW of Pangai, TongaFebruary 27, 1905 · 292 km N of this epicenter
- 6.7south of the Fiji IslandsSeptember 8, 1920 · 249 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1937M8.1
Fiji Islands
16 Apr 1937 · 181 km away
- 1903M8.0
Tonga Islands
4 Jan 1903 · 264 km away
- 1948M7.9
Tonga Islands
8 Sep 1948 · 213 km away
tsunami
- 1853
Tonga Trench
24 Dec 1853 · 133 km away
tsunami
- 1907
S Of Tonga
1907 · 131 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.