M5.1 earthquake 30 km W of San Antonio, Chile

Monday, September 20, 2010, 05:42:56 UTC · 33.643°S, 71.928°W

A magnitude 5.1 earthquake struck 30 km W of San Antonio, Chile on Monday, September 20, 2010, 05:42:56 UTC, at a depth of 30.4 km (shallow). USGS received 62 “Did You Feel It?” reports, with a maximum reported intensity of V (moderate). It is the strongest earthquake within 300 km since an M5.1 on September 13, 2010.

Magnitude: 5.1; Moderate · mwc
Depth: 30 km; Shallow
Felt reports: 62; Max intensity V
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 75 km aftershock search area

In context

How big was it, and why here?

Energy released

674 tons of TNT

That is about 1/22 of the Hiroshima bomb. It released about 1 times the energy of a magnitude 5.0.

Tectonic setting

90 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

30 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	III · Weak	37	125 km
Viña del Mar, Valparaíso, Chile	III · Weak	13	84 km
San Antonio, Valparaíso, Chile	V · Moderate	4	42 km
Valparaíso, Valparaíso, Chile	III · Weak	2	78 km
Quilpué, Valparaíso, Chile	II · Weak	2	83 km
Rengo, Libertador General Bernardo OʿHiggins, Chile	IV · Light	1	133 km
Chillán, Bío Bío, Chile	III · Weak	1	329 km
Machalí, Libertador General Bernardo OʿHiggins, Chile	II · Weak	1	134 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 75 km

USGS lists 5 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M4.9 on October 11, 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 658 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 39 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 35,590 recorded deaths. The most severe:

1939M8.3
Chillan
25 Jan 1939 · 291 km away · intensity X
30,000 deaths$920 million damagetsunami
1906M8.2
South Central
17 Aug 1906 · 72 km away · intensity XI
4,000 deaths$100 million damagetsunami
2010M8.8
Maule, Concepcion, Talcahuano
27 Feb 2010 · 289 km away · intensity IX
558 deaths$30 billion damagetsunami
1965M7.3
Central
28 Mar 1965 · 154 km away
400 deaths$125 million damage
1928M7.6
Talca, Chillan, Santiago, San Fernando
1 Dec 1928 · 151 km away · intensity IX
279 deathsSevere damage ($5–24M)tsunami
1985M8.0
Central Coast, San Antonio, Valparaiso
3 Mar 1985 · 60 km away · intensity VIII
180 deaths$1.5 billion damagetsunami

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

Nearby trackers