Earthquakes in St. Helena through history

The deadliest was not the strongest: an earthquake in May 1821 (Britian), for which NOAA records 3 deaths. NOAA’s list of significant earthquakes has 1 here, back to 1821. NOAA’s record here begins in May 1821 with an earthquake (Britian). NOAA lists one tsunami that began in or off St. Helena.

• August 10, 2011Earthquake · M 6.0221 km ENE of Georgetown, Saint HelenaUSGS
• March 7, 2001Earthquake · M 6.0206 km NE of Georgetown, Saint HelenaUSGS
• March 10, 1947Earthquake · M 6.1144 km SSE of Georgetown, Saint HelenaUSGS
• November 8, 1922Earthquake · M 6.1245 km ENE of Georgetown, Saint HelenaUSGS
• May 1821EarthquakeBritian · 3 deaths (NOAA)NOAA NCEI
• May 1821TsunamiSt HelenaNOAA NCEI

• An event counts for St. Helena 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 St. Helena 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 St. Helena, 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