M7.6 earthquake 34 km S of Limón, Costa Rica

Monday, April 22, 1991, 21:56:51 UTC · 9.685°N, 83.073°W

A magnitude 7.6 earthquake struck 34 km S of Limón, Costa Rica on Monday, April 22, 1991, 21:56:51 UTC, at a depth of 10.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.

Magnitude: 7.6; Major · mw
Depth: 10 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VIII; Severe (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

3.8 megatons of TNT

That is about 252 times the Hiroshima bomb. It released about 7,943 times the energy of a magnitude 5.0.

Tectonic setting

21 km

from the nearest mapped plate boundary, between the Panama and Caribbean plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

10 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 32 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.2 on May 4, 1991. 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 200 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 37 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 871 recorded deaths. The most severe:

1910M6.4
Cartago, San Jose
4 May 1910 · 107 km away
700 deathsSevere damage ($5–24M)
1991M7.6
Limon, Pandora; Panama
22 Apr 1991 · 0 km away · intensity X
90 deaths$510 million damagetsunami
1952
Costa Rica
30 Dec 1952 · 83 km away
29 deaths
1973M6.5
Tilaran, Arenal, Rio Chiquito
14 Apr 1973 · 215 km away
26 deathsUnder $1 million damage
1955M5.8
Costa Rica
1 Sep 1955 · 160 km away
10 deathsModerate damage ($1–5M)
1941M7.6
Costa Rica-Panama
5 Dec 1941 · 110 km away · intensity IV
6 deathsModerate damage ($1–5M)tsunami

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

Nearby trackers