The predecessor of the 2011 Tohoku earthquake is
considered to be the 869 Jogan earthquake.
A national history book depicts strong ground shakings,
collapse of houses, kilometers of tsunami flooding with
1000 drowned people in Sendai plain in AD 869 in
Jogan era. In addition, paleoseismological studies found
tsunami deposits in coastal lowlands, more than 4 km
from the current coast in the Sendai plain. Older
tsunami deposits were also found. From the distribution
of the tsunami deposits and computed inundation area,
the size (M = 8.3 to 8.4), location and fault models of the
Jogan earthquake were proposed with a recurrence interval
between 500 and 1000 years.