Reviewed by USGS6y ago
M6.1 earthquake in Chagos Archipelago region
Monday, August 31, 2020, 17:24:04 UTC · 4.016°S, 70.197°E
A magnitude 6.1 earthquake struck in Chagos Archipelago region on Monday, August 31, 2020, 17:24:04 UTC, at a depth of 10.0 km (shallow). USGS received 7 “Did You Feel It?” reports, with a maximum reported intensity of IV (light). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.6 on July 15, 2003.
- Magnitude
- 6.1
- Strong · mww
- Depth
- 10 km
- Shallow
- Felt reports
- 7
- Max intensity IV
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- Green
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
21 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 45 times the energy of a magnitude 5.0.
Tectonic setting
171 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
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| Hithadhoo, Siin, Maldives | II · Weak | 2 | 496 km |
| Fuvammulah, Ghaviyani, Maldives | I · Not felt | 1 | 546 km |
| Mundhoo, Laam, Maldives | I · Not felt | 1 | 762 km |
| Malé, Malé, Maldives | I · Not felt | 1 | 976 km |
| Hulhudhoo, Siin, Maldives | I · Not felt | 1 | 507 km |
USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No populated area was estimated to feel noticeable shaking.
After the main event
Aftershocks within 100 km
USGS lists 2 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M4.4 on September 8, 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 104 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 regionSeptember 12, 1965 · 274 km S of this epicenter
- 6.2Chagos Archipelago regionMay 11, 1912 · 274 km S of this epicenter
- 6.0Chagos Archipelago regionFebruary 22, 1956 · 221 km W of this epicenter
- 6.0Chagos Archipelago regionOctober 2, 1957 · 262 km S of this epicenter
- 5.9Chagos Archipelago regionNovember 11, 1967 · 268 km SE of this epicenter
- 5.9Chagos Archipelago regionMarch 2, 1968 · 273 km SE of this epicenter
- 5.9Chagos Archipelago regionMarch 31, 1970 · 78 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:
- 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.