Reviewed by USGS8y ago
M5.8 earthquake in Ascension Island region
Friday, October 5, 2018, 14:59:44 UTC · 5.691°S, 11.525°W
A magnitude 5.8 earthquake struck in Ascension Island region on Friday, October 5, 2018, 14:59:44 UTC, at a depth of 10.0 km (shallow). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M6.0 on August 10, 2011.
- Magnitude
- 5.8
- Moderate · mww
- Depth
- 10 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- II
- Weak (ShakeMap)
- PAGER alert
- Green
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
8 kilotons of TNT
That is about 1/2 of the Hiroshima bomb. It released about 16 times the energy of a magnitude 5.0.
Tectonic setting
30 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
Modelled from the ShakeMap and population data. Alert level green: low likelihood of casualties and damage.
- II · Weak shaking
- 1,500 people
Estimated shaking in nearby towns
- GeorgetowncapitalPopulation 538II · Weak
After the main event
Aftershocks within 75 km
USGS lists 1 M2.5+ earthquake within 75 km in the following 30 days; the largest was M5.1 on October 5, 2018. 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 109 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.1245 km ENE of Georgetown, Saint HelenaNovember 8, 1922 · 168 km SW of this epicenter
- 6.0221 km ENE of Georgetown, Saint HelenaAugust 10, 2011 · 193 km SW of this epicenter
- 6.0206 km NE of Georgetown, Saint HelenaMarch 7, 2001 · 197 km SW of this epicenter
- 5.9Ascension Island regionMarch 27, 1952 · 161 km S of this epicenter
- 5.9Ascension Island regionApril 30, 1932 · 17 km E of this epicenter
- 5.8north of Ascension IslandSeptember 1, 1914 · 207 km NW of this epicenter
- 5.8Ascension Island regionJune 7, 1961 · 19 km N of this epicenter
- 5.7126 km ENE of Georgetown, Saint HelenaJuly 12, 2001 · 281 km SW of this epicenter