At about 780-750 BC, a major earthquake struck southeast Sweden. At Brantetrask, the bedrock of quartzite was heavily fractured into big, flat blocks. Local people turned the site into a quarry for flat blocks to be placed around the Late Bronze Age graves at Brantevik, the big flat blocks of the sarcophagus, and two 5 tons monoliths transported 30 km to the SSW and erected as the bow and stern stones in the huge ship monument of Ales Stones. Rock carvings from the Bronze Age at Jarrestad became traversed by numerous fractures. Similar rock carving fracturing was observed at six other sites within a radius of 5 km from Brantetrask. In the shore cliff at Ales Stones a seismite was recorded and dated at 780-750 BC. At Glimme hallar, 4 km WSW of Brantevik, the bedrock shows signs of young tectonization. At Lillehem, 40 km to the NNW of Brantetrask, seismically disturbed beds were recorded and dated at the Late Holocene. The seismic event is concluded to have occurred around 780-750 cal.yrs BC and to have had a magnitude in the order of 6.3 to 6.8 and an intensity of about IX on the IES scale.