M6.9 earthquake in Vanuatu region

Saturday, October 9, 2021, 10:58:31 UTC · 21.189°S, 174.522°E

A magnitude 6.9 earthquake struck in Vanuatu region on Saturday, October 9, 2021, 10:58:31 UTC, at a depth of 535.0 km (deep). USGS received 18 “Did You Feel It?” reports, with a maximum reported intensity of IV (light). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.3 on October 2, 2021.

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: 6.9; Strong · mww
Depth: 535 km; Deep
Felt reports: 18; Max intensity IV
Est. shaking: III; Weak (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: Flag; Check tsunami.gov

Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

338 kilotons of TNT

That is about 22 times the Hiroshima bomb. It released about 708 times the energy of a magnitude 5.0.

Tectonic setting

42 km

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

Depth: deep

535 km

Deep earthquakes (over 300 km) happen deep inside subducting plates. They rarely cause damage, but can be felt faintly over very large distances.

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
Suva, Central, Fiji Islands	II · Weak	2	754 km
Isangel, Tafea, Vanuatu	II · Weak	2	787 km
Nadi, Western, Fiji Islands	II · Weak	2	720 km
Opotiki, Bay of Plenty, New Zealand	II · Weak	2	1964 km
Deuba, Central, Fiji Islands	IV · Light	1	719 km
Deception Bay, Queensland, Australia	III · Weak	1	2345 km
Hamilton, Waikato, New Zealand	II · Weak	1	1916 km
Labasa, Northern, Fiji Islands	II · Weak	1	906 km
Ba, Western, Fiji Islands	II · Weak	1	747 km
Lautoka, Western, Fiji Islands	II · Weak	1	733 km
Sigatoka, Western, Fiji Islands	II · Weak	1	705 km
Yaté, Sud, New Caledonia	II · Weak	1	959 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.

III · Weak shaking: 929,000 people
II · Weak shaking: 618,000 people

After the main event

Aftershocks within 100 km

USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M5.4 on October 12, 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.

5.4Vanuatu region5y ago · 24 km S of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 247 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 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1990M7.6
Fiji Islands
3 Mar 1990 · 123 km away
1944M7.5
Loyalty Islands
5 Oct 1944 · 298 km away
2016M7.2
Loyalty Islands
12 Aug 2016 · 204 km away · intensity VI
tsunami
2017M6.9
Fiji Islands
3 Jan 2017 · 257 km away · intensity VI
tsunami

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

Nearby trackers