QuakeScout
Magnitude4.7

Reviewed by USGS5y ago

M4.7 earthquake southeast of the Loyalty Islands

Sunday, August 29, 2021, 03:37:12 UTC · 23.301°S, 171.552°E

A magnitude 4.7 earthquake struck southeast of the Loyalty Islands on Sunday, August 29, 2021, 03:37:12 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M5.2 on August 10, 2021.

Magnitude
4.7
Light · mb
Depth
10 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: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

169 tons of TNT

That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.

Tectonic setting

20 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

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 lists 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.4 on September 1, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M51h6h1d3d7d14d30dMainshock M4.7
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.4southeast of the Loyalty Islands5y ago · 23 km S of this epicenter
  2. 4.3southeast of the Loyalty Islands5y ago · 50 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,061 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.7southeast of the Loyalty IslandsFebruary 10, 2021 · 30 km N of this epicenter
  2. 7.7249 km E of Vao, New CaledoniaMay 16, 1995 · 172 km W of this epicenter
  3. 7.6274 km ESE of Tadine, New CaledoniaMarch 16, 1928 · 158 km NW of this epicenter
  4. 7.5southeast of the Loyalty IslandsJanuary 4, 1998 · 129 km NW of this epicenter
  5. 7.5166 km ESE of Tadine, New CaledoniaDecember 5, 2018 · 265 km NW of this epicenter
  6. 7.3201 km ESE of Tadine, New CaledoniaDecember 27, 2003 · 232 km NW of this epicenter
  7. 7.2southeast of the Loyalty IslandsNovember 14, 1906 · 85 km N 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:

  1. 1901M7.9

    Loyalty Islands

    9 Aug 1901 · 215 km away

    Moderate damage ($1–5M)tsunami

  2. 2018M7.5

    Loyalty Islands

    5 Dec 2018 · 265 km away · intensity III

    Limited damage (under $1M)tsunami

  3. 1995M7.7

    Noumea; Vanuatu: Port-Vila

    16 May 1995 · 172 km away · intensity III

    tsunami

  4. 2021M7.7

    Loyalty Islands

    10 Feb 2021 · 28 km away · intensity VII

    tsunami

  5. 1928M7.5

    Loyalty Islands

    16 Mar 1928 · 180 km away

  6. 1943M7.5

    Loyalty Islands

    14 Sep 1943 · 155 km away

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

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