Reviewed by USGSCosta Rica88y ago
M6.8 earthquake 13 km W of Jacó, Costa Rica
Friday, December 22, 1939, 04:44:03 UTC · 9.610°N, 84.751°W
A magnitude 6.8 earthquake struck 13 km W of Jacó, Costa Rica on Friday, December 22, 1939, 04:44:03 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on December 21, 1939.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 25 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
256 kilotons of TNT
That is about 17 times the Hiroshima bomb. It released about 537 times the energy of a magnitude 5.0.
Tectonic setting
81 km
from the nearest mapped plate boundary, between the Cocos and Panama plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
25 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 100 km
USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M6.1 on December 23, 1939. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 41 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.64 km WNW of Atenas, Costa RicaDecember 21, 1939 · 56 km NE of this epicenter
- 7.392 km SW of San Juan del Sur, NicaraguaDecember 30, 1907 · 224 km NW of this epicenter
- 7.353 km SSE of Quepos, Costa RicaDecember 20, 1904 · 106 km SE of this epicenter
- 7.3204 km WSW of Sámara, Costa RicaFebruary 27, 1916 · 284 km W of this epicenter
- 7.16 km WNW of Siquirres, Costa RicaApril 24, 1916 · 141 km NE of this epicenter
- 6.847 km S of Masachapa, NicaraguaOctober 2, 1932 · 279 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 23 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 700 recorded deaths. The most severe:
- 1910M6.4
Cartago, San Jose
4 May 1910 · 93 km away
700 deathsSevere damage ($5–24M)
- 1854M7.3
Costa Rica-Panama
5 Aug 1854 · 228 km away
Severe damage ($5–24M)tsunami
- 1925M6.7
Managua
5 Oct 1925 · 292 km away
Severe damage ($5–24M)
- 1922M6.4
Nicaragua
16 Feb 1922 · 239 km away
Severe damage ($5–24M)
- 1888
San Jose, Ala Juela, Heredia
30 Dec 1888 · 81 km away · intensity VIII
Severe damage ($5–24M)
- 1898M7.9
Leon, Chinandega, Managua
29 Apr 1898 · 299 km away · intensity VIII
Moderate damage ($1–5M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.