M7.4 earthquake 292 km SW of Vaini, Tonga

Thursday, May 23, 2013, 17:19:04 UTC · 23.009°S, 177.232°W

A magnitude 7.4 earthquake struck 292 km SW of Vaini, Tonga on Thursday, May 23, 2013, 17:19:04 UTC, at a depth of 173.7 km (intermediate). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.6 on March 19, 2009.

Tsunami flagUSGS sets this flag for large events in oceanic regions so tsunami warning centers review them. It does not by itself mean a tsunami occurred. Check tsunami.gov and local authorities for official messages.

Magnitude: 7.4; Major · mww
Depth: 174 km; Intermediate
Felt reports: 0; Did You Feel It?
Est. shaking: VI; Strong (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: Flag; Check tsunami.gov

Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

1.9 megatons of TNT

That is about 126 times the Hiroshima bomb. It released about 3,981 times the energy of a magnitude 5.0.

Tectonic setting

32 km

from the nearest mapped plate boundary, between the Tonga and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: intermediate

174 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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 populated area was estimated to feel noticeable shaking.

After the main event

Aftershocks within 200 km

USGS lists 8 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.5 on June 1, 2013. 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 1,808 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 10 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 · 137 km away · intensity IV
1 death$1 million damagetsunami
1937M8.1
Fiji Islands
16 Apr 1937 · 169 km away
1975M7.8
S Of Tonga
11 Oct 1975 · 300 km away
1982M7.7
Tonga Trench
19 Dec 1982 · 187 km away
tsunami
1997M7.7
Tonga Islands
14 Oct 1997 · 111 km away
tsunami
2002M7.7
Fiji Islands
19 Aug 2002 · 276 km away

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

Nearby trackers