Reviewed by USGS42y ago
M7.1 earthquake central Mid-Atlantic Ridge
Thursday, November 1, 1984, 04:48:50 UTC · 8.185°N, 38.794°W
A magnitude 7.1 earthquake struck central Mid-Atlantic Ridge on Thursday, November 1, 1984, 04:48:50 UTC, at a depth of 10.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 7.1
- Major · mw
- 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: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
674 kilotons of TNT
That is about 45 times the Hiroshima bomb. It released about 1,413 times the energy of a magnitude 5.0.
Tectonic setting
2 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 200 km
USGS lists 1 M2.5+ earthquake within 200 km in the following 30 days; the largest was M4.8 on November 22, 1984. 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 47 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.8central Mid-Atlantic RidgeApril 21, 1919 · 201 km NW of this epicenter
- 6.8central Mid-Atlantic RidgeNovember 17, 1963 · 163 km E of this epicenter
- 6.7central Mid-Atlantic RidgeApril 24, 1947 · 12 km SE of this epicenter
- 6.4central Mid-Atlantic RidgeSeptember 12, 1915 · 170 km E of this epicenter
- 6.4central Mid-Atlantic RidgeJuly 20, 1906 · 154 km E of this epicenter
- 6.4central Mid-Atlantic RidgeSeptember 25, 1958 · 58 km W of this epicenter
- 6.3central Mid-Atlantic RidgeDecember 7, 1915 · 25 km N of this epicenter
- 6.3central Mid-Atlantic RidgeSeptember 14, 1945 · 142 km SE of this epicenter