Reviewed by USGSArgentina56y ago
M6.9 earthquake 99 km WNW of San Antonio de los Cobres, Argentina
Sunday, February 21, 1971, 10:35:22 UTC · 23.780°S, 67.177°W
A magnitude 6.9 earthquake struck 99 km WNW of San Antonio de los Cobres, Argentina on Sunday, February 21, 1971, 10:35:22 UTC, at a depth of 189.0 km (intermediate). It is the strongest earthquake within 300 km since an M8.2 on December 9, 1950.
- Magnitude
- 6.9
- Strong · mw
- Depth
- 189 km
- Intermediate
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- V
- Moderate (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
304 kilotons of TNT
That is about 20 times the Hiroshima bomb. It released about 638 times the energy of a magnitude 5.0.
Tectonic setting
252 km
from the nearest mapped plate boundary, between the Altiplano and South American plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: intermediate
189 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 100 km
USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 29 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.2121 km SSE of San Pedro de Atacama, ChileDecember 9, 1950 · 78 km W of this epicenter
- 7.187 km SSE of Antofagasta, ChileJuly 8, 1942 · 298 km W of this epicenter
- 6.930 km SSE of Santa Clara, ArgentinaAugust 25, 1948 · 283 km E of this epicenter
- 6.881 km WSW of Calama, ChileDecember 23, 1916 · 276 km NW of this epicenter
- 6.840 km SE of San Pedro de Atacama, ChileAugust 3, 1962 · 101 km NW of this epicenter
- 6.7136 km NNE of Calama, ChileDecember 27, 1967 · 293 km NW of this epicenter
- 6.6176 km S of San Pedro de Atacama, ChileJune 11, 1970 · 152 km SW of this epicenter
- 6.647 km ENE of Humahuaca, ArgentinaMay 12, 1959 · 245 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 37 recorded deaths. The most severe:
- 1930M6.1
La Poma
24 Dec 1930 · 231 km away · intensity VIII
31 deathsSevere damage ($5–24M)
- 1953M7.4
Northern
7 Dec 1953 · 243 km away
3 deaths$7 million damage
- 1936M7.3
Taltal
13 Jul 1936 · 297 km away
1 deathModerate damage ($1–5M)tsunami
- 1971M6.3
Catalina, Antofagasta
17 Jun 1971 · 280 km away · intensity V
1 deathModerate damage ($1–5M)
- 1950M8.0
Chile-Argentina
9 Dec 1950 · 45 km away · intensity VII
1 death
- 1844M6.5
Salta, Jujuy, Tucuman
19 Oct 1844 · 181 km away · intensity VII
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.