Fig. 4

Graphical depiction of method for computing times and heights of high waters and low waters on November 28 and 29, by means of interpolation of predicted and observed heights outside that time window. a Overview of tide table predictions (color) and gauged water levels (black curve and circles) November 26 to December 1, along with high waters and low waters computed in b. Each dotted line is a cubic spline fit to the four lunar-day sets of high waters and low waters, and the associated tide table predictions are keyed by color to Fig. 3. b Computation of times and heights for November 28 and 29 (bold) for each of the four lunar-day sets. The splines in a (dotted color lines) are reproduced separately in (b) for each set. Ratios of predicted intervals between lunar-day tides (upper bracket with each set) are projected onto a slightly adjusted timeline controlled at its ends by high water and low water times gauged November 27 and November 30, outside the time of the tsunami (lower bracket). Evaluating the splines at the computed times gives the computed heights