Time Reversal Imaging of the Tsunami Source

In this paper, we apply time reversal imaging (TRI) to the problem of reconstructing the initial sea surface displacement that generates a tsunami. We discuss theoretical considerations in the application of TRI to the tsunami problem, including time reversibility and reciprocity of the shallow-water equations. Several numerical experiments are conducted to establish the efficacy of TRI in the tsunami context. TRI is applied to observations of the tsunami generated by the Tohoku earthquake on March 11, 2011, for which an unprecedented number of high-quality observations are available. Finally, we compare the findings of the TRI results with other, more conventional methods of source inversion. Results indicate that TRI is effective for imaging a tsunami source when a sufficient number of observations are available. Because it involves fewer assumptions about the nature of the tsunami source, in particular those regarding source location and fault geometry, we believe that TRI has the potential to improve our understanding of tsunami generation—for example, through detection of non-seismic components of the tsunami source.