Seismic hazard assessment of the East Thuringian region/Germany - Case study

East Thuringia/Germany, especially the region Gera-Ronneburg, is part of the large Kyffhauser-Jachymov-Fault-Zone and displays moderate seismicity. However, its seismic hazard is significantly higher than that of the surrounding area including the Vogtland/Northern Bohemian region. The earthquake catalogue of Germany contains for this region besides the well investigated Central German Earthquake (March 1872, I-0=VII-VIII) entries of up to I-0=VIII (14th century). Epicentral intensities and coordinates of these historical earthquakes are considered as uncertain. In seismic hazard analysis historical events which are uncertain are often neglected. Bur, especially in regions of moderate seismicity and infrequent larger earthquakes, the time window considered should be extended as far as possible. Apart from the necessity to study the historical sources of the strongest 14th century earthquakes, we investigate the influence of these events an the seismic hazard, laking into account the uncertainties of their size and location. Generally, the investigations clearly reveal the importance of defining source regions on the one hand and the significance of the local relevant attenuation function on the other hand. A further important point in seismic hazard assessment is the strong influence of the geological site conditions on seismic hazard (amplification or damping phenomena). For both points the well-known Central German Earthquake (1872) supplies important information.