October 18, 1848 Tsunami: Wellington, New Zealand

1848, October 19, 05:33 [local time, Oct 18 17:33 UTC]. The policeman standing on the Hutt bridge before sunrise of the 19th, saw the river greatly agitated, and two or three seconds afterwards, felt the ground shock beneath his fee. A high tide was observed in Wellington.

On October 19 agitation in the Hutt River on preceded or accompanied the large aftershock at around 5 am. A very high tide occurred in Wellington at an unspecified time. Hansard (1848) account was written some months after the earthquakes and has less credibility than accounts written at the time. The source of the agitation is therefore uncertain. If the timing is only slightly incorrect and the agitation occurred at the time of the earthquake it could represent seiching, or shaking effects on the sediments in the river. It is inconsistent with tsunami. Eiby (1980) argues that the observer may have been mistaken as to the time and the possibility of tsunami is not precluded. Nevertheless, a tsunami was not observed elsewhere and agitation of ponds and rivers is a common effect of strong shaking and the passage of seismic waves.

The high tide can be explained by a high MHPWS tide, which was marginally higher than that on October 18. Presumably it was not accompanied by storm surge and therefore not alarming. Hence, the occurrence of a tsunami on 19 October 1848 is given a validity of 0 (erroneous).

(above from Reference #5324).