M7.4 earthquake 54 km WSW of Diego de Almagro, Chile

Tuesday, October 4, 1983, 18:52:13 UTC · 26.535°S, 70.563°W

A magnitude 7.4 earthquake struck 54 km WSW of Diego de Almagro, Chile on Tuesday, October 4, 1983, 18:52:13 UTC, at a depth of 14.8 km (shallow). It is the strongest earthquake within 300 km since an M7.7 on December 28, 1966.

Magnitude: 7.4; Major · mw
Depth: 15 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 earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

1.9 megatons of TNT

That is about 126 times the Hiroshima bomb. It released about 3,981 times the energy of a magnitude 5.0.

Tectonic setting

115 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

15 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 lists 12 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.7 on October 9, 1983. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 199 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 30 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 722 recorded deaths. The most severe:

1922M8.5
Atacama
11 Nov 1922 · 208 km away · intensity XI
700 deathsSevere damage ($5–24M)tsunami
1859M7.6
Chile
5 Oct 1859 · 93 km away · intensity X
10 deathsUnder $1 million damagetsunami
1983M7.3
Northern: Copoapo-Chanaral
4 Oct 1983 · 0 km away · intensity VII
5 deaths$1 million damagetsunami
1966M7.8
Taltal, Catalina
28 Dec 1966 · 116 km away · intensity VIII
3 deathsUnder $1 million damagetsunami
1946M7.9
Northern
2 Aug 1946 · 7 km away
2 deathsSevere damage ($5–24M)tsunami
1936M7.3
Taltal
13 Jul 1936 · 233 km away
1 deathModerate damage ($1–5M)tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers