The dam at Kremasta was begun building on July 4th 1964 and completed on July 4th 1965 with the trucks running 3 shifts, 24 hours per day by Kaiser Engineering and Construction of Oakland,Ca (we lived there in the American construction camp from September 1965 until September 1966). The earthquakes began in about April or May and quickly averaged 2 or 3 per day, the local talk was -naturally- that the dam had been built on an earthquake fault line and that the pressure of the water behind the dam was causing the quakes. This was the accepted answer.