Shattering

Earthquakes are quite rightly feared by people - in a few seconds they destroy houses and roads, fell trees and tear open deep crevices in the earth’s surface. This can result in rockslides, landslides and tsunamis.

And the catastrophe doesn’t stop with the quaking: people lose not only the roof over their heads but also foodstuffs are lost, drinking water is contaminated. Damaged gas and electricity lines can lead to extensive fires. When a region is affected by a strong earthquake, even work places are lost as a result.

Earthquakes are naturally triggered and non-controllable natural phenomenon. The earth seems static to us, but it is continually moving. Like a puzzle of various parts, the rigid earth plates with land masses and oceans lie on the softer earth mantel of hot formable rock. Because the earth attempts to balance the temperatures between the hot core and the cooler earth’s surfaces, warmer materials rise slowly and cooler ones sink down from the surface. (Ill. A) Something similar happens in a pot of water that is brought to a boil. The water first warms on the stove top, the warm water rises and the cooler water on the surface sinks. (Ill. B)

Through these compensation motions (convection streams), the earth plates move on the surface. These movements could happen towards one another, over one another or away from one another. Since the earth plates are rigid and not malleable, they hook into one another and, through this pressure over time, enormous tension builds up. These are released at some time in a jerky movement, whereby enormous energy is released and lets the earth quake!

The tension in Carinthia is developed through the movement of the Adriatic plate that moves north toward the Eurasian plate. (Ill C) Through the collision of these plates, the fold mountains of the Alps were formed, whereby the Adriatic plate moved under the European. Through the pressure and tension a thick fracture zone network developed that in the mountains can be traced through the large valleys.

At the local fracture zones in Carinthia, there are on the average six perceivable earthquake events per year as well as numerous weaker quakes. Seismic activity is known, above all, along the fracture zone of Straßburg/St. Veit, of Gmünd/Katschberg or the Feistritz Valley, as well as from the northwestern part of the Lavant Valley. Also the side movements of the periadriatic seam that runs in Carinthia through the Gail Valley, the Rose Valley and the Karawanken Mountains, is a seismic active zone. Besides that, one can also feel in Carinthia the stronger earthquakes from the neighbouring countries Slovenia and Italy.

Damage to building happens only rarely, about every 40 to 50 years. Weaker quakes that are measurable but not perceivable occur much more frequently. On the homepage of the GeoSphere (https://geoweb.zamg.ac.at/live_seis/pages/frame.php) the current earthquake measurements can be followed live.