Reviewed by USGSChile56y ago
M6.4 earthquake 49 km WNW of La Ligua, Chile
Sunday, July 11, 1971, 09:51:39 UTC · 32.299°S, 71.726°W
A magnitude 6.4 earthquake struck 49 km WNW of La Ligua, Chile on Sunday, July 11, 1971, 09:51:39 UTC, at a depth of 39.5 km (shallow). It is the strongest earthquake within 300 km since an M7.8 on July 9, 1971.
- Magnitude
- 6.4
- Strong · mw
- Depth
- 40 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- 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
60 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 126 times the energy of a magnitude 5.0.
Tectonic setting
97 km
from the nearest mapped plate boundary, between the Nazca and South American plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
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 100 km
USGS lists 4 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.6 on July 31, 1971. 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 82 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 · 33 km E of this epicenter
- 8.145 km NNW of Illapel, ChileApril 6, 1943 · 120 km N of this epicenter
- 7.819 km NNE of Hacienda La Calera, ChileJuly 9, 1971 · 63 km SE of this epicenter
- 7.47 km SSE of La Ligua, ChileMarch 28, 1965 · 54 km SE of this epicenter
- 7.237 km S of San Antonio, ChileMarch 18, 1931 · 182 km S of this epicenter
- 7.060 km WSW of Coquimbo, ChileApril 19, 1955 · 242 km N of this epicenter
- 6.972 km WNW of Calingasta, ArgentinaJuly 27, 1917 · 215 km NE of this epicenter
- 6.957 km W of Ovalle, ChileFebruary 15, 1917 · 198 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 34 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 18,584 recorded deaths. The most severe:
- 1861
Mendoza, San Luiz
20 Mar 1861 · 280 km away · intensity IX
14,000 deathsExtreme damage ($25M+)tsunami
- 1906M8.2
South Central
17 Aug 1906 · 82 km away · intensity XI
4,000 deaths$100 million damagetsunami
- 1965M7.3
Central
28 Mar 1965 · 51 km away
400 deaths$125 million damage
- 1971M7.8
Central
9 Jul 1971 · 54 km away · intensity IX
83 deaths$236 million damagetsunami
- 1822M8.5
Valparaiso, Quillota, Concon, Aconcagua
20 Nov 1822 · 82 km away · intensity XI
72 deathsExtreme damage ($25M+)tsunami
- 1943M8.2
Illapel
6 Apr 1943 · 174 km away
11 deathsLimited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.