Tonga Tsunami at Port Otago 

Data kindly supplied by Port Otago Ltd.

Commentary

The Spit at the entrance to Otago Harbour is sheltered from far infra gravity ( FIG ) waves, so the tsunami waves stand out. They started arriving about 6 h after the earthquake and peaked about 12 h after the tsunami. The outer embayment from the harbour has a seiche period of 25 minutes and this seiche appears to have been excited by the tsunami.

Figure 1. Tonga tsunami at The Spit, Port Otago 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?
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