Reviewed by USGSChile96y ago
M7.2 earthquake 37 km S of San Antonio, Chile
Wednesday, March 18, 1931, 08:02:24 UTC · 33.926°S, 71.556°W
A magnitude 7.2 earthquake struck 37 km S of San Antonio, Chile on Wednesday, March 18, 1931, 08:02:24 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.2 on December 2, 1928.
- Magnitude
- 7.2
- Major · mw
- Depth
- 35 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VII
- Very strong (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
951 kilotons of TNT
That is about 63 times the Hiroshima bomb. It released about 1,995 times the energy of a magnitude 5.0.
Tectonic setting
128 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
35 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 200 km
USGS has not published any M2.5+ earthquake within 200 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 24 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 · 170 km N of this epicenter
- 7.730 km NNE of Constitución, ChileDecember 1, 1928 · 144 km SW of this epicenter
- 7.7103 km NW of Constitución, ChileJanuary 30, 1914 · 186 km SW of this epicenter
- 7.247 km NW of Cauquenes, ChileDecember 2, 1928 · 226 km SW of this epicenter
- 6.7210 km WNW of Valparaíso, ChileDecember 11, 1904 · 269 km NW of this epicenter
- 6.599 km SE of Rengo, ChileJanuary 30, 1914 · 183 km SE of this epicenter
- 6.517 km NNE of Hacienda La Calera, ChileOctober 17, 1930 · 148 km N of this epicenter
- 6.358 km WNW of La Ligua, ChileOctober 2, 1906 · 196 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 25 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 18,358 recorded deaths. The most severe:
- 1861
Mendoza, San Luiz
20 Mar 1861 · 285 km away · intensity IX
14,000 deathsExtreme damage ($25M+)tsunami
- 1906M8.2
South Central
17 Aug 1906 · 111 km away · intensity XI
4,000 deaths$100 million damagetsunami
- 1928M7.6
Talca, Chillan, Santiago, San Fernando
1 Dec 1928 · 126 km away · intensity IX
279 deathsSevere damage ($5–24M)tsunami
- 1822M8.5
Valparaiso, Quillota, Concon, Aconcagua
20 Nov 1822 · 111 km away · intensity XI
72 deathsExtreme damage ($25M+)tsunami
- 1730M9.1
Valparaiso
8 Jul 1730 · 159 km away · intensity XI
5 deathsSevere damage ($5–24M)tsunami
- 1880M7.7
Illapel
15 Aug 1880 · 259 km away · intensity X
2 deathsSevere damage ($5–24M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.