M4.7 earthquake 25 km WSW of Arauco, Chile

Wednesday, April 21, 2010, 03:52:02 UTC · 37.321°S, 73.589°W

A magnitude 4.7 earthquake struck 25 km WSW of Arauco, Chile on Wednesday, April 21, 2010, 03:52:02 UTC, at a depth of 35.0 km (shallow). USGS received 4 “Did You Feel It?” reports, with a maximum reported intensity of III (weak). It is the strongest earthquake within 300 km since an M5.2 on April 19, 2010.

Magnitude: 4.7; Light · mb
Depth: 35 km; Shallow
Felt reports: 4; Max intensity III
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

169 tons of TNT

That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.

Tectonic setting

84 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

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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
Santiago, Metropolitana, Chile	II · Weak	2	506 km
San Fernando, Libertador General Bernardo OʿHiggins, Chile	III · Weak	1	385 km
Copiapó, Atacama, Chile	II · Weak	1	1146 km

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 50 km

USGS lists 17 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.4 on May 3, 2010. 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 369 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 26 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 33,253 recorded deaths. The most severe:

1939M8.3
Chillan
25 Jan 1939 · 169 km away · intensity X
30,000 deaths$920 million damagetsunami
1960M9.5
Puerto Montt, Valdivia
22 May 1960 · 93 km away · intensity XII
2,226 deaths$1.0 billion damagetsunami
2010M8.8
Maule, Concepcion, Talcahuano
27 Feb 2010 · 147 km away · intensity IX
558 deaths$30 billion damagetsunami
1928M7.6
Talca, Chillan, Santiago, San Fernando
1 Dec 1928 · 295 km away · intensity IX
279 deathsSevere damage ($5–24M)tsunami
1751M8.5
Concepcion, Chillan, Talca, Tutuben, Curico
25 May 1751 · 182 km away · intensity XI
65 deathsSevere damage ($5–24M)tsunami
1949M7.3
Angol, Traiguen
20 Apr 1949 · 76 km away
57 deathsModerate damage ($1–5M)tsunami

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

Nearby trackers