by Risa Wolf

Created on: November 22, 2011   Last Updated: November 23, 2011

At 5:17 a.m. on July 26, 1963, Skopje, the capital and administrative center of the Macedonian Republic of the former Yugoslavia, was destroyed by an earthquake. The earthquake registered 6.9 on the Richter scale (9 on the Mercali scale); the results were devastating. Lasting 20 seconds, the seismic waves left more than 1,000 people dead, more than 3,300 seriously injured, and 130,000 people instantly homeless. The quake destroyed or severely damaged houses, apartment buildings, schools, hospitals, and factories; further, both post office and railroad station were demolished and left the area without external communications. Built on both sides of the valley of the Vardar River, the city sits on a known and active fault line, the epicenter was in the center of the city of 178,000 people, and buildings were not constructed to resist earthquakes.

The site

Skopje sits in the valley of the Vardar River. It is surrounded by mountains cut by gorges that, when flooded, flow into the river. The river basin itself is flat and marshy to the east. Originally built on the right bank, the city grew in all directions, including across the river to the left bank. In 1950, more than 3,000 apartment units were built to house the expanding population that made Skopje the third largest city in Yugoslavia. Macedonia is mountainous, which has consequences when an earthquake strikes where magnitude (Richter) or intensity (Mercali) depends upon the wave types, among other elements.

Seismic wave types

P-waves: P, or Primary waves are the rolling waves and they travel through rock and water. They move rapidly at 6-13 km/sec.

S-waves: S, or Shear waves are generally larger than P-waves and cause the most damage. They are slower than P-waves at 3.5- 7.5 km/sec. S-waves cannot move through liquids. 

L-waves: L, or Love (named after A.E.H. Love) move up and down on the surface and create the most intense shaking at the end of an earthquake.

Because both P-waves and S-waves move through rock, they can be felt at a distance from the epicenter. All of Macedonia felt the earthquake, though in varying intensities. The mountain ranges in Macedonia are contiguous with mountain ranges to both east and west. The quake was strongly felt at more distant sites. It was felt in Sofia, Bulgaria – 173 km away, and at Thessalonki, Greece - 195 km away. It also was felt, although much attenuated, in Marseilles, France—1,351 km and 57-60 minutes wave-time away. That is approximately one

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