M3.9 earthquake 18 km NNE of Náfpaktos, Greece

Wednesday, August 18, 2004, 14:38:59 UTC · 38.550°N, 21.910°E

A magnitude 3.9 earthquake struck 18 km NNE of Náfpaktos, Greece on Wednesday, August 18, 2004, 14:38:59 UTC, at a depth of 24.0 km (shallow).

Magnitude: 3.9; Minor · ml
Depth: 24 km; Shallow
Felt reports: 0; Did You Feel It?
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

11 tons of TNT

That is about 1/1,410 of the Hiroshima bomb. A magnitude 5.0 releases about 45 times more energy.

Tectonic setting

18 km

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

Depth: shallow

24 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 50 km

USGS lists 22 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.0 on August 26, 2004. 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 555 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 177 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 8,561 recorded deaths. The most severe:

1851M6.6
Vlore (Valona),Berat; Turkey
12 Oct 1851 · 288 km away · intensity XI
2,000 deathsExtreme damage ($25M+)tsunami
1750
Morea,Cerigo
7 Jun 1750 · 278 km away · intensity X
2,000 deaths
1953M7.2
Lixouri-Argostoli (Kephallenia)
12 Aug 1953 · 101 km away · intensity X
476 deaths$100 million damagetsunami
1851
Berat
17 Oct 1851 · 288 km away · intensity X
400 deathsSevere damage ($5–24M)
1820M6.9
Zakinthos (Zante)
29 Dec 1820 · 106 km away · intensity X
388 deathsSevere damage ($5–24M)tsunami
1886M6.8
Triphylie (Peleponese), Philiatra
27 Aug 1886 · 162 km away · intensity X
326 deathsSevere damage ($5–24M)tsunami

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

Nearby trackers