The 1847 Zenkoji earthquake (善光寺地震, Zenkōji jishin) occurred at about 21:30 local time on 8 May at Nagano, Japan. It had a magnitude of 7.4 on the surface-wave magnitude scale. It caused the destruction of many houses in Nagano and at least 8,600 people were killed. The earthquake triggered many landslides, the largest of which dammed the Sai River (a tributary of the Shinano River). 19 days later, the failure of this earthquake dam caused a flood that destroyed many more houses and killed 35 people.
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