February 5, 1966 Earthquake: Central, Greece

February 5, 1966, 02:01:48.3 UTC, central Greece, 39.2 N, 22 E, depth 38 km, magnitude 6.25. One person was killed and 50 were injured by this earthquake that caused extensive property damage at Krenti, Kliston, Fournia, Alestia, and surrounding villages. Several landslides caused additional damage throughout the area by blocking roads and covering houses with tons of rock and earth. The number of homeless was reported to be in the thousands. (reference #45)

$4 million damage. (reference #1250)

On 5 February 1966 a strong earthquake of magnitude 6.3 occurred in Evritania; it was preceded by a series of slight tremors. The principal shock (Feb 5) caused serious damage in a dozen mountain villages, particularly at Fournas, Alestia, Kleisto and Vracha; 450 houses were destroyed, 1,200 seriously damaged. There was 1 death and 60 injured, 4 of whom seriously; numerous landslides and ground fractures were noticed.

The Greek seismological service published the following in its bulletin of February 1966:

An exceptionally long sequence of small local shocks with exponentially increasing frequency preceded the principal shock. The sequence started after the damming of the Akheloos River and the impounding of the artificial Lake Kremasta. It was found that the numbers of the foreshocks could be correlated with increasing of reservoir loading. There seem, therefore, to be good reasons for believing that the tectonic equilibrium in the area of Kremasta was sufficiently ripe to be disturbed by this comparatively minor additional unilateral load. The weight of the water in the new lake is of the order of 4.7 x 109 tons.

Evritania is a seismic region, but from 1951 to 1965 the epicentres were localized in the lower Akheloos valley, about 40 km downstream from the dam. This dam, built across the Akheloos near the Kremasta thermal springs, started filling with water on 21 July 1965. From November 1965, the level of the lake rose rapidly; the first tremors were felt in January 1966 and the principal shock occurred on 5 February when the lake had almost reached its maximum height: the depth of the water was then about 120 metres. Numerous aftershocks (more than 160) were felt or recorded; they were localized either near the lake or in the mountainous area to the north-east of the dam; at least 5 of the aftershocks were of magnitude greater than 5: 5 February, 8 March, 3 April, 4 May, and 11 June.

The lake rests on eocene-oligocene flysch; however, about 11 km to the north of the dam, the lake covers an area of large faults at the contact between the flysch and the Jurassic limestone of Gavrovon: it is in this latter area that the premonitory tremors and the strongest aftershocks occurred. A further violent tremor occurred on 29 October, 1966.

(above from reference #1039)