Reviewed by USGS5y ago
M4.6 earthquake southeast of the Loyalty Islands
Wednesday, August 11, 2021, 04:09:44 UTC · 22.795°S, 172.120°E
A magnitude 4.6 earthquake struck southeast of the Loyalty Islands on Wednesday, August 11, 2021, 04:09:44 UTC, at a depth of 43.4 km (shallow). It is the strongest earthquake within 300 km since an M5.2 on August 10, 2021.
- Magnitude
- 4.6
- Light · mb
- Depth
- 43 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 earthquake
In context
How big was it, and why here?
Energy released
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
42 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
43 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 50 km
USGS has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,083 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.7southeast of the Loyalty IslandsFebruary 10, 2021 · 55 km SW of this epicenter
- 7.7249 km E of Vao, New CaledoniaMay 16, 1995 · 229 km W of this epicenter
- 7.6274 km ESE of Tadine, New CaledoniaMarch 16, 1928 · 184 km W of this epicenter
- 7.5southeast of the Loyalty IslandsJanuary 4, 1998 · 136 km NW of this epicenter
- 7.5166 km ESE of Tadine, New CaledoniaDecember 5, 2018 · 292 km W of this epicenter
- 7.3201 km ESE of Tadine, New CaledoniaDecember 27, 2003 · 257 km W of this epicenter
- 7.2southeast of the Loyalty IslandsNovember 14, 1906 · 59 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1901M7.9
Loyalty Islands
9 Aug 1901 · 235 km away
Moderate damage ($1–5M)tsunami
- 2018M7.5
Loyalty Islands
5 Dec 2018 · 292 km away · intensity III
Limited damage (under $1M)tsunami
- 1995M7.7
Noumea; Vanuatu: Port-Vila
16 May 1995 · 229 km away · intensity III
tsunami
- 2021M7.7
Loyalty Islands
10 Feb 2021 · 60 km away · intensity VII
tsunami
- 1928M7.5
Loyalty Islands
16 Mar 1928 · 189 km away
- 1943M7.5
Loyalty Islands
14 Sep 1943 · 145 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.