Reviewed by USGSChile55y ago
M5.6 earthquake 38 km WSW of La Ligua, Chile
Saturday, July 31, 1971, 22:08:48 UTC · 32.540°S, 71.625°W
A magnitude 5.6 earthquake struck 38 km WSW of La Ligua, Chile on Saturday, July 31, 1971, 22:08:48 UTC, at a depth of 39.9 km (shallow). It is the strongest earthquake within 300 km since an M6.4 on July 11, 1971.
- Magnitude
- 5.6
- Moderate · mw
- Depth
- 40 km
- Shallow
- 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
4 kilotons of TNT
That is about 1/4 of the Hiroshima bomb. It released about 8 times the energy of a magnitude 5.0.
Tectonic setting
109 km
from the nearest mapped plate boundary, between the Nazca and South American plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
40 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 75 km
USGS has not published any M2.5+ earthquake within 75 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 87 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.2The 1906 Valparaiso, Chile EarthquakeAugust 17, 1906 · 26 km NE of this epicenter
- 8.145 km NNW of Illapel, ChileApril 6, 1943 · 144 km N of this epicenter
- 7.819 km NNE of Hacienda La Calera, ChileJuly 9, 1971 · 44 km E of this epicenter
- 7.730 km NNE of Constitución, ChileDecember 1, 1928 · 289 km S of this epicenter
- 7.7103 km NW of Constitución, ChileJanuary 30, 1914 · 292 km SW of this epicenter
- 7.47 km SSE of La Ligua, ChileMarch 28, 1965 · 39 km E of this epicenter
- 7.237 km S of San Antonio, ChileMarch 18, 1931 · 154 km S of this epicenter
- 7.060 km WSW of Coquimbo, ChileApril 19, 1955 · 270 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 36 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 18,863 recorded deaths. The most severe:
- 1861
Mendoza, San Luiz
20 Mar 1861 · 266 km away · intensity IX
14,000 deathsExtreme damage ($25M+)tsunami
- 1906M8.2
South Central
17 Aug 1906 · 62 km away · intensity XI
4,000 deaths$100 million damagetsunami
- 1965M7.3
Central
28 Mar 1965 · 43 km away
400 deaths$125 million damage
- 1928M7.6
Talca, Chillan, Santiago, San Fernando
1 Dec 1928 · 276 km away · intensity IX
279 deathsSevere damage ($5–24M)tsunami
- 1971M7.8
Central
9 Jul 1971 · 40 km away · intensity IX
83 deaths$236 million damagetsunami
- 1822M8.5
Valparaiso, Quillota, Concon, Aconcagua
20 Nov 1822 · 62 km away · intensity XI
72 deathsExtreme damage ($25M+)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.