The tsunami waveform data are used to estimate the
water height, or fault slip, distribution at the source. In
this method, called tsunami waveform inversion,
the tsunami source or fault plane is divided into subfaults,
and tsunami waveforms, or the Green’s functions,
are computed for each of the subfault with unit
amount of slip. Assuming that the observed tsunami
waveforms are linear superposition of the Green’s
function, the distribution of displacement or fault slip
can be estimated using a least-square method. The tsunami
waveform inversion is used to study the tsunami
sources. For the 2011 Tohoku earthquake, because
high-quality and high-sampling offshore tsunami waveforms
were available, the temporal change as well as
spatial distribution of the slips on subfaults was estimated.