Reviewed by USGSSaint Helena15y ago
M6.0 earthquake 221 km ENE of Georgetown, Saint Helena
Wednesday, August 10, 2011, 23:45:43 UTC · 7.040°S, 12.618°W
A magnitude 6.0 earthquake struck 221 km ENE of Georgetown, Saint Helena on Wednesday, August 10, 2011, 23:45:43 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M6.0 on March 7, 2001.
- Magnitude
- 6.0
- Strong · mww
- 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
15 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 32 times the energy of a magnitude 5.0.
Tectonic setting
8 km
from the nearest mapped plate boundary, between the African 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 100 km
USGS lists 3 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.2 on August 11, 2011. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 88 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.1144 km SSE of Georgetown, Saint HelenaMarch 10, 1947 · 283 km SW of this epicenter
- 6.1245 km ENE of Georgetown, Saint HelenaNovember 8, 1922 · 25 km NE of this epicenter
- 6.0206 km NE of Georgetown, Saint HelenaMarch 7, 2001 · 41 km NW of this epicenter
- 5.9Ascension Island regionMarch 27, 1952 · 127 km E of this epicenter
- 5.9Ascension Island regionApril 30, 1932 · 201 km NE of this epicenter
- 5.8Ascension Island regionJune 7, 1961 · 206 km NE of this epicenter
- 5.7126 km ENE of Georgetown, Saint HelenaJuly 12, 2001 · 94 km SW of this epicenter
- 5.7249 km ENE of Georgetown, Saint HelenaMarch 29, 1964 · 32 km E of this epicenter