Tsunami models indicate that the source of the 2011
earthquake appear to be a combination of the 1896
Sanriku “tsunami earthquake” and a Jogan-type deeper
interplate earthquake. A huge slip near the trench
axis, similar to the 1896 Sanriku tsunami earthquake,
caused the first impulsive tsunami waves recorded by the
bottom pressure and GPS wave gauges and large tsunami
runup heights along Sanriku coast. The fault motion
and large slip along the deeper plate interface, similar
to a proposed model of the Jogan earthquake,
produced a long-wavelength seafloor displacement which
caused the first gradual rise at offshore gauges
and the large tsunami inundation in the Sendai plain.