The majority of the Haut-Rhin "département", including Fessenheim, is classified as being in a zone of moderate seismicity; the southern third is in a medium-risk zone. The most recent earthquake in this zone, with a magnitude 4.7, took place in this southern third at Sierentz in July 1980. The last major earthquake in the region was the 1356 Basel earthquake, estimated to have had a Mw magnitude of up to 7.1.