QuakeScout
Magnitude6.9

Reviewed by USGSCosta Rica86y ago

M6.9 earthquake 112 km SSW of Quepos, Costa Rica

Saturday, December 6, 1941, 21:24:49 UTC · 8.531°N, 84.637°W

A magnitude 6.9 earthquake struck 112 km SSW of Quepos, Costa Rica on Saturday, December 6, 1941, 21:24:49 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.5 on December 5, 1941.

Magnitude
6.9
Strong · mw
Depth
15 km
Shallow
Felt reports
0
Did You Feel It?
Est. shaking
V
Moderate (ShakeMap)
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

388 kilotons of TNT

That is about 26 times the Hiroshima bomb. It released about 813 times the energy of a magnitude 5.0.

Tectonic setting

21 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

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 100 km

USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 54 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.64 km WNW of Atenas, Costa RicaDecember 21, 1939 · 164 km N of this epicenter
  2. 7.544 km ESE of Burica, PanamaJuly 18, 1934 · 246 km E of this epicenter
  3. 7.570 km WSW of Golfito, Costa RicaDecember 5, 1941 · 106 km E of this epicenter
  4. 7.353 km SSE of Quepos, Costa RicaDecember 20, 1904 · 81 km NE of this epicenter
  5. 7.16 km WNW of Siquirres, Costa RicaApril 24, 1916 · 211 km NE of this epicenter
  6. 6.8south of PanamaJuly 18, 1934 · 275 km SE of this epicenter
  7. 6.813 km W of Jacó, Costa RicaDecember 22, 1939 · 121 km N of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 20 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 706 recorded deaths. The most severe:

  1. 1910M6.4

    Cartago, San Jose

    4 May 1910 · 178 km away

    700 deathsSevere damage ($5–24M)

  2. 1941M7.6

    Costa Rica-Panama

    5 Dec 1941 · 159 km away · intensity IV

    6 deathsModerate damage ($1–5M)tsunami

  3. 1854M7.3

    Costa Rica-Panama

    5 Aug 1854 · 180 km away

    Severe damage ($5–24M)tsunami

  4. 1888

    San Jose, Ala Juela, Heredia

    30 Dec 1888 · 168 km away · intensity VIII

    Severe damage ($5–24M)

  5. 1822M7.6

    Matina

    7 May 1822 · 210 km away · intensity VII

    Moderate damage ($1–5M)tsunami

  6. 1844M7.4

    Rivas, Greytown

    May 1844 · 297 km away

    Moderate damage ($1–5M)tsunami

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

Nearby trackers

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