Reviewed by USGS40y ago
M4.6 earthquake in Carlsberg Ridge
Sunday, September 28, 1986, 21:37:49 UTC · 10.636°N, 57.063°E
A magnitude 4.6 earthquake struck in Carlsberg Ridge on Sunday, September 28, 1986, 21:37:49 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M6.2 on September 17, 1986.
- 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
17 km
from the nearest mapped plate boundary, between the Indian and Somali 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.2 on September 29, 1986. 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 35 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.1Owen Fracture Zone regionMarch 31, 1954 · 200 km NE of this epicenter
- 7.0Carlsberg RidgeOctober 3, 1904 · 9 km W of this epicenter
- 6.7Owen Fracture Zone regionApril 8, 1983 · 101 km NE of this epicenter
- 6.7170 km E of Hadibu, YemenDecember 18, 1908 · 262 km NW of this epicenter
- 6.5Carlsberg RidgeJuly 7, 1986 · 37 km SW of this epicenter
- 6.2Owen Fracture Zone regionApril 20, 1980 · 141 km NE of this epicenter
- 6.2Carlsberg RidgeSeptember 17, 1986 · 18 km SW of this epicenter
- 6.2Carlsberg RidgeApril 11, 1954 · 12 km E of this epicenter