Tonga Tsunami at Gisborne 

Data kindly supplied by Eastland Port

Commentary

Gisborne has ubiquitous infra gravity ( IG ) waves of 33 s period that are aliased by 1-minute sampling, thus causing the noisy signal leading up to 4 May. The tsunami waves are easily identifiable, having much longer periods. The first waves arrived in mid-morning, about 6 h after the earthquake.

Figure 1. Tonga tsunami at Gisborne showing: A. long wave record; B. significant (red) and maximum (blue) wave heights, and high tide times (green diamonds); C. period of significant waves; and D. distribution of significant wave height with time and period. EQ denotes the time of the earthquake. Times are in NZST (UTC + 12).

How were these calculated?
Return to top
Back to Map