QuakeScout
Magnitude4.6

Reviewed by USGS4y ago

M4.6 earthquake in South Sandwich Islands region

Thursday, November 11, 2021, 10:17:52 UTC · 56.207°S, 25.725°W

A magnitude 4.6 earthquake struck in South Sandwich Islands region on Thursday, November 11, 2021, 10:17:52 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M4.8 on November 10, 2021.

Magnitude
4.6
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

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

24 km

from the nearest mapped plate boundary, between the Sandwich and South American 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 M4.6 on November 13, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M4.6
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.4South Sandwich Islands region4y ago · 44 km SE of this epicenter
  2. 4.6South Sandwich Islands region4y ago · 42 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,495 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.12021 South Sandwich Islands EarthquakeAugust 12, 2021 · 243 km S of this epicenter
  2. 8.11929 South Sandwich Islands EarthquakeJune 27, 1929 · 245 km W of this epicenter
  3. 7.8South Sandwich Islands regionMay 26, 1964 · 120 km W of this epicenter
  4. 7.5South Sandwich Islands regionAugust 12, 2021 · 157 km S of this epicenter
  5. 7.2South Sandwich Islands regionDecember 27, 1991 · 34 km NE of this epicenter
  6. 7.2South Sandwich Islands regionMay 28, 2016 · 75 km W of this epicenter
  7. 7.1South Sandwich Islands regionSeptember 8, 1961 · 101 km W of this epicenter
  8. 7.1South Sandwich Islands regionDecember 11, 2018 · 263 km S of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1929M8.1

    South Sandwich Islands

    27 Jun 1929 · 245 km away

  2. 2021M8.1

    South Sandwich Islands

    12 Aug 2021 · 247 km away

    tsunami

  3. 1961M7.7

    South Sandwich Islands

    5 Sep 1961 · 214 km away

  4. 1961M7.7

    South Sandwich Islands

    8 Sep 1961 · 96 km away

  5. 2021M7.5

    South Sandwich Islands

    12 Aug 2021 · 158 km away

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

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