Preliminary investigation on the historical M8 earthquake occurred in 7 BC at Baotou, Inner Mongolia

A historical M8 earthquake occurred on November 11, 7 BC (September Bingchen, the second year of Suihe, Han dynasty) has not been incorporated in the chinese historical earthquake catalogs, as the historical records are ambiguous. A lot of pieces of broken potsherds, bricks and tile-ends with words were found by archaeological excavation in the coffin of ancient tomb at Machi ancient town of Baotou. These were the broken pieces of daily use potteries and the destructive building wastes, and the house was completed built during 52 BC (the second year of Ganlu) to 33 BC (the first year of Jingning). According to historical materials a strong earthquake occurred during this period and the city walls of more than 30 places in northern prefectures were damaged and 400 people were killed, while more than 200 persons were killed at Machi ancient town which was destroyed and then disappeared. Therefore, the destroyed buildings buried before the late Western Han dynasty might be caused by the strong earthquake and other natural disasters or wars. With additional information on the seismic ground deformation, which are estimated to form 2000 years ago and found along the front fault of Daqinshan, it is suggested that the event occurred on Novemher 11, 7 BC, at Machi ancient town of Baotou, Inner Mogolia, can be named as Baotou earthquake with M8 and meizoseismal intensity X.