Reviewed by USGSTonga44y ago
M5.6 earthquake 268 km SSW of ‘Ohonua, Tonga
Tuesday, December 28, 1982, 15:53:51 UTC · 23.687°S, 175.592°W
A magnitude 5.6 earthquake struck 268 km SSW of ‘Ohonua, Tonga on Tuesday, December 28, 1982, 15:53:51 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.6 on December 23, 1982.
- Magnitude
- 5.6
- Moderate · ms
- 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
4 kilotons of TNT
That is about 1/4 of the Hiroshima bomb. It released about 8 times the energy of a magnitude 5.0.
Tectonic setting
16 km
from the nearest mapped plate boundary, between the Kermadec and Tonga 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 3 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.1 on January 21, 1983. 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 411 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 · 143 km S of this epicenter
- 7.6south of the Fiji IslandsDecember 18, 1963 · 173 km SW of this epicenter
- 7.4south of TongaMarch 18, 1905 · 235 km E of this epicenter
- 7.3south of the Fiji IslandsJanuary 20, 1970 · 297 km SW of this epicenter
- 7.2south of the Fiji IslandsNovember 24, 1960 · 129 km SW of this epicenter
- 7.2south of TongaOctober 10, 1977 · 242 km S of this epicenter
- 7.2south of TongaDecember 19, 1982 · 57 km SW of this epicenter
- 6.8Tonga regionJune 22, 1977 · 95 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1 recorded deaths. The most severe:
- 1977M7.2
Tonga Trench
22 Jun 1977 · 95 km away · intensity IV
1 death$1 million damagetsunami
- 1937M8.1
Fiji Islands
16 Apr 1937 · 283 km away
- 1975M7.8
S Of Tonga
11 Oct 1975 · 143 km away
- 1982M7.7
Tonga Trench
19 Dec 1982 · 57 km away
tsunami
- 1963M7.5
Tonga Trench
18 Dec 1963 · 161 km away
tsunami
- 1977M7.2
Tonga Trench
10 Oct 1977 · 242 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.