QuakeScout
Magnitude6.8

Reviewed by USGS18y ago

M6.8 earthquake in South Sandwich Islands region

Saturday, February 23, 2008, 15:57:20 UTC · 57.335°S, 23.433°W

A magnitude 6.8 earthquake struck in South Sandwich Islands region on Saturday, February 23, 2008, 15:57:20 UTC, at a depth of 14.0 km (shallow). It is the strongest earthquake within 300 km since an M7.2 on December 27, 1991.

Magnitude
6.8
Strong · mwc
Depth
14 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: 100 km aftershock search area

In context

How big was it, and why here?

Energy released

239 kilotons of TNT

That is about 16 times the Hiroshima bomb. It released about 501 times the energy of a magnitude 5.0.

Tectonic setting

43 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

14 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 100 km

USGS lists 4 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.1 on February 26, 2008. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M5M6M71h6h1d3d7d14d30dMainshock M6.8
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 5.1South Sandwich Islands region18y ago · 16 km N of this epicenter
  2. 4.4South Sandwich Islands region18y ago · 64 km NW of this epicenter
  3. 4.9South Sandwich Islands region18y ago · 21 km N of this epicenter
  4. 5.0South Sandwich Islands region18y ago · 35 km N of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 797 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8South Sandwich Islands regionMay 26, 1964 · 280 km W of this epicenter
  2. 7.3South Sandwich Islands regionSeptember 1, 1961 · 292 km SW of this epicenter
  3. 7.2South Sandwich Islands regionNovember 15, 1910 · 200 km S of this epicenter
  4. 7.2South Sandwich Islands regionDecember 27, 1991 · 183 km NW of this epicenter
  5. 7.1South Sandwich Islands regionSeptember 8, 1961 · 263 km NW of this epicenter
  6. 7.1east of the South Sandwich IslandsAugust 26, 1977 · 288 km SE of this epicenter
  7. 6.8South Sandwich Islands regionNovember 2, 1943 · 171 km W of this epicenter
  8. 6.7South Sandwich Islands regionDecember 31, 1963 · 183 km NW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 2 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1961M7.7

    South Sandwich Islands

    5 Sep 1961 · 225 km away

  2. 1961M7.7

    South Sandwich Islands

    8 Sep 1961 · 263 km away

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

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