Earthquakes in British Indian Ocean Territory through history
From 1900 to October 19, 2026, USGS recorded 5 earthquakes of magnitude 6 or more in or off British Indian Ocean Territory. One stands far above the rest: a magnitude 7.3 on November 30, 1983 (Chagos Archipelago region). The next strongest reached 6.3.
The last 30 days · as of
USGS recorded no earthquake of magnitude 4.5 or more in the area the map frames in the last 30 days.
What the record holds
NOAA’s list of significant earthquakes has 1 here, back to 1912. NOAA records no deaths for it. NOAA’s record here begins on November 30, 1983 with an earthquake (Chagos Archipelago region). NOAA lists one tsunami that began in or off British Indian Ocean Territory, and one from elsewhere that reached it with deaths or a metre of water or more. The highest water NOAA records here was 1.9 m, on December 26, 2004.
The events
- December 26, 2004Tsunami · 1.9 m hereOff W. Coast Of SumatraNOAA NCEI · Wikipedia
- September 19, 1984Earthquake · M 6.0Chagos Archipelago regionUSGS
- December 3, 1983Earthquake · M 6.3Chagos Archipelago regionUSGS
- November 30, 1983Earthquake · M 7.3Chagos Archipelago regionUSGS · NOAA NCEI · Wikipedia
- September 12, 1965Earthquake · M 6.3Chagos Archipelago regionUSGS
- May 11, 1912Earthquake · M 6.2Chagos Archipelago regionUSGS
Good to know
- An event counts for British Indian Ocean Territory when it began inside its borders, or at sea within 100 km of its coast (so one can count for two neighbours), or further out, up to 300 km, where British Indian Ocean Territory is the nearest country.
- USGS counts here start at magnitude 6: the catalogue’s smaller quakes thin out going back, where few instruments listened.
- NOAA lists significant events only: earthquakes that killed, did about $1 million of damage, reached magnitude 7.5 or intensity X, or raised a tsunami, and eruptions and tsunamis by like measures. Magnitudes before 1900 are its estimates from written accounts.
- Deaths are NOAA’s total for each event, wherever people died, its tsunami and fires included. A tsunami counts the dead its runup records give for this place: NOAA’s total for a tsunami includes its source quake’s.
- A tsunami from elsewhere counts where one of its runups killed or rose a metre or more.
- The map frames the box around British Indian Ocean Territory, its neighbours’ quakes included, so its count runs higher than this page’s.
- Counted to October 19, 2026, as is the map. The last 30 days ask USGS again.
How the layers work, where their data comes from and what they can’t tell you: Earthquakes, live, The world through history