Two earth tremors hit eastern Switzerland on Tuesday night without causing serious damage or casualties. Although earthquakes in Switzerland are rarely severe, Switzerland is still considered seismically active.

Two earth tremors hit eastern Switzerland on Tuesday night without causing serious damage or casualties. Although earthquakes in Switzerland are rarely severe, Switzerland is still considered seismically active.

In an extensive study, the Swiss Seismological Institute in Zürich recorded a total of 226 earthquakes in Switzerland in 1998. The majority of them were in cantons Valais and Graubünden.

Tuesday's tremors occurred near the Graubünden resort of Klosters, and the other was in the Rheintal region of St. Gallen. They measured 3.3 and 3.6 on the Richter scale respectively - regarded as average intensity for Swiss earthquakes.

The canton of Graubünden is sparsely populated and does not have any critical installations like nuclear power stations. Valais, however, has Switzerland's largest high-altitude dams, where a large amount of electricity is produced. The dams have so far survived decades of seismic activity very well, reducing fears of a major catastrophe.

The cause of the relatively high degree of seismic activity in Canton Valais is attributed to the motion of two "plates". Scientists say that "Africa begins in Valais", the place where the Central European Plate meets the North African Plate. It was their collision that formed the Alps.

One city, Basel, lives with a constant threat of a major earthquake. It was destroyed by an earthquake in 1356.

Basel is the site of the so-called "Rhine Trench", a geological anomaly similar to the famous St. Andreas Fault running through California. This is why, seismically-speaking, Basel is often referred to as "The San Francisco of Switzerland".

By Bob Zanotti

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