M7.2 earthquake south of Tonga

Monday, October 10, 1977, 11:53:53 UTC · 25.856°S, 175.406°W

A magnitude 7.2 earthquake struck south of Tonga on Monday, October 10, 1977, 11:53:53 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.8 on October 11, 1975.

Magnitude: 7.2; Major · 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: 200 km aftershock search area

In context

How big was it, and why here?

Energy released

951 kilotons of TNT

That is about 63 times the Hiroshima bomb. It released about 1,995 times the energy of a magnitude 5.0.

Tectonic setting

1 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 200 km

USGS lists 10 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.4 on October 10, 1977. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 189 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1955M7.8
Kermadec Islands
27 Feb 1955 · 239 km away
1975M7.8
S Of Tonga
11 Oct 1975 · 111 km away
1961M7.5
Kermadec Islands
7 Mar 1961 · 273 km away
1963M7.5
Tonga Trench
18 Dec 1963 · 168 km away
tsunami
1977M7.2
Tonga Trench
10 Oct 1977 · 0 km away
tsunami
1956M7.0
Tonga Islands
10 Jan 1956 · 23 km away

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers