Reviewed by USGS6y ago
M4.7 earthquake in Chagos Archipelago region
Thursday, October 1, 2020, 21:07:29 UTC · 4.200°S, 70.039°E
A magnitude 4.7 earthquake struck in Chagos Archipelago region on Thursday, October 1, 2020, 21:07:29 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M4.7 on September 30, 2020.
- Magnitude
- 4.7
- 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
169 tons of TNT
That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.
Tectonic setting
148 km
from the nearest mapped plate boundary, between the Indian and Somali plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.4 on October 3, 2020. 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 108 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.6Carlsberg RidgeJuly 15, 2003 · 256 km NW of this epicenter
- 6.3Chagos Archipelago regionDecember 3, 1983 · 294 km SE of this epicenter
- 6.3Chagos Archipelago regionSeptember 12, 1965 · 259 km S of this epicenter
- 6.2Chagos Archipelago regionMay 11, 1912 · 259 km S of this epicenter
- 6.1Chagos Archipelago regionAugust 31, 2020 · 27 km NE of this epicenter
- 6.0Chagos Archipelago regionFebruary 22, 1956 · 209 km W of this epicenter
- 6.0Chagos Archipelago regionOctober 2, 1957 · 239 km S of this epicenter
- 5.9Chagos Archipelago regionNovember 11, 1967 · 260 km SE 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:
- 2003M7.6
Felt In Maldives
15 Jul 2003 · 256 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.