M7.7 earthquake southeast of the Loyalty Islands

Wednesday, February 10, 2021, 13:19:55 UTC · 23.051°S, 171.657°E

A magnitude 7.7 earthquake struck southeast of the Loyalty Islands on Wednesday, February 10, 2021, 13:19:55 UTC, at a depth of 10.0 km (shallow). USGS received 7 “Did You Feel It?” reports, with a maximum reported intensity of IX (violent). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.7 on May 16, 1995.

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: 7.7; Major · mww
Depth: 10 km; Shallow
Felt reports: 7; Max intensity IX
Est. shaking: IV; Light (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

5.4 megatons of TNT

That is about 355 times the Hiroshima bomb. It released about 11,220 times the energy of a magnitude 5.0.

Tectonic setting

9 km

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

Depth: shallow

10 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
Vila, Shefa, Vanuatu	IV · Light	2	683 km
Mont-Doré, Sud, New Caledonia	VII · Very strong	1	528 km
Vao, Sud, New Caledonia	V · Moderate	1	430 km
Isangel, Tafea, Vanuatu	IV · Light	1	461 km

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

Modelled from the ShakeMap and population data. Alert level green: low likelihood of casualties and damage.

IV · Light shaking: 126,000 people
III · Weak shaking: 108,000 people
II · Weak shaking: 8,800 people

Estimated shaking in nearby towns

NoumeacapitalPopulation 93,000IV · Light
Mont-DorePopulation 25,000IV · Light
DumbeaPopulation 19,000III · Weak
TadinePopulation 7,500III · Weak
VaoPopulation 1,900III · Weak
PaitaPopulation 13,000III · Weak
IsangelcapitalPopulation 1,400III · Weak
WecapitalPopulation 10,000III · Weak

After the main event

Aftershocks within 200 km

USGS lists 356 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.3 on February 10, 2021. 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 988 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 14 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1901M7.9
Loyalty Islands
9 Aug 1901 · 206 km away
Moderate damage ($1–5M)tsunami
2018M7.5
Loyalty Islands
5 Dec 2018 · 260 km away · intensity III
Limited damage (under $1M)tsunami
1995M7.7
Noumea; Vanuatu: Port-Vila
16 May 1995 · 180 km away · intensity III
tsunami
2021M7.7
Loyalty Islands
10 Feb 2021 · 6 km away · intensity VII
tsunami
1928M7.5
Loyalty Islands
16 Mar 1928 · 167 km away
1943M7.5
Loyalty Islands
14 Sep 1943 · 135 km away

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

Nearby trackers