For many years most modern large wind turbines were erected in areas like Denmark and northern Germany, where earthquakes are rare and normally weak. However, more recently wind farms have been developed in Asia, Africa and southern Europe, where strong earthquakes are much more likely to occur. As a consequence, the question arises as to how wind turbines perform in an earthquake of a given magnitude, and especially to what extent the stability of the overall structure and integrity of the machinery are guaranteed. This article describes how building codes for seismic loading of structures are used for site approvals for wind farms and shows results for the simulated dynamical behaviour of a wind turbine in an earthquake. The simulation has been carried out with the new simulation code SiWEC, which is also introduced in this article.