Reviewed by USGS43y ago
M7.3 earthquake in Chagos Archipelago region
Wednesday, November 30, 1983, 17:46:00 UTC · 6.852°S, 72.110°E
A magnitude 7.3 earthquake struck in Chagos Archipelago region on Wednesday, November 30, 1983, 17:46:00 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
- 7.3
- 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 areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
1.3 megatons of TNT
That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.
Tectonic setting
6 km
from the nearest mapped plate boundary, between the Indian and Australian 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 69 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.3 on December 3, 1983. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.9Chagos Archipelago region43y ago · 97 km W of this epicenter
- 5.2Chagos Archipelago region43y ago · 87 km W of this epicenter
- 5.1Chagos Archipelago region43y ago · 110 km W of this epicenter
- 4.5Chagos Archipelago region43y ago · 12 km SE of this epicenter
- 4.7Chagos Archipelago region43y ago · 42 km NW of this epicenter
- 4.6Chagos Archipelago region43y ago · 84 km W of this epicenter
- 5.1Chagos Archipelago region43y ago · 80 km W of this epicenter
- 5.1Chagos Archipelago region43y ago · 21 km NE of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 9 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.3Chagos Archipelago regionSeptember 12, 1965 · 159 km W of this epicenter
- 6.2Chagos Archipelago regionMay 11, 1912 · 155 km W of this epicenter
- 6.0Chagos Archipelago regionOctober 2, 1957 · 274 km W of this epicenter
- 5.9Chagos Archipelago regionNovember 11, 1967 · 116 km NW of this epicenter
- 5.9Chagos Archipelago regionMarch 2, 1968 · 110 km NW of this epicenter
- 5.7Chagos Archipelago regionNovember 11, 1967 · 127 km NW of this epicenter
- 5.6Chagos Archipelago regionNovember 11, 1967 · 119 km NW of this epicenter
- 5.6Chagos Archipelago regionNovember 10, 1967 · 126 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 1 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1983M7.6
Chagos Archipelago: Diego Garcia
30 Nov 1983 · 0 km away · intensity VI
Limited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.