The 869 Jogan Sanriku earthquake (869年三陸地震 869-nen Sanriku jishin) and associated tsunami struck the area around Sendai in the northern part of Honshu on 9 July 869 (26th day of 5th month, 11th year of Jōgan).[2] The earthquake had an estimated magnitude of 8.6 on the surface wave magnitude scale.[3] The tsunami caused widespread flooding of the Sendai plain, with sand deposits being found up to 4 kilometres (2.5 mi) from the coast.