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The video in this tweet shows the small wave produced at Tokomaru Bay in New Zealand following the M 8.1 - Kermadec Islands, New Zealand 2021-03-04 19:28:31 (UTC) event. These are so far the only thing I've seen in terms of "data" on waves produced by the quake.

Warnings went out and people did rapidly evacuate low elevation coastal areas as a precaution.

Question: Are there any potential measurements of any transient sea-level changes via buoys or perhaps even satellite (e.g. radar, laser), either likely very small ones out at sea or larger ones nearby the coast where the height would be amplified?

Or is all information going to be basically anecdotal?

The data doesn't necessarily have to be available yet, I'm just curious about what measurement capability exists.

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    $\begingroup$ Not an expert in the field, but I know the waves have been recorded by several tide gauges in the Pacific. See for instance this station: ioc-sealevelmonitoring.org/station.php?code=gbit If you look at data from 2021-03-05, there is a lot a variation in relative sea level, which is due to the passage of the waves (you can compare with any other day, they don't show this pattern). But I don't know how these variations in sea level can be interpreted in terms of wave height. $\endgroup$ – Jean-Marie Prival Mar 5 at 10:18
  • $\begingroup$ Thank you for the source! Interesting! I think that disturbances in northern New Zealand related to this quake should be seen within two or three hours. The distance from the reported epicenter to the buoy you link to is about 985 km and the speed of the wave in deeper water is about 950 km/hr. I don't see any disturbance at the 1 hour mark but it does start to get noisy at the 2 hour mark and that continues until about the 6 hour mark after the original quake. I'm not very knowledgable in this field, so I don't know how to interpret this. $\endgroup$ – uhoh Mar 5 at 10:42
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Norfolk Island experienced a tsunami wave 64 cm tall. In Australia the tsunami wave was 10 cm at Tweed Heads and 9 cm at Port Kembla. In Vanuatu the height was 32 cm and in Fiji 13 cm and 8 cm in Tonga.

Australian Burea of Meteorology report

TSUNAMI DETAILS: The following sea level gauges have observed a tsunami, heights refer to wave amplitudes (positive wave values):

Name                  Country       Lat     Lon      Height (m)  Time (UTC)
East Cape             NEW ZEALAND   37.50S  178.17E  0.15        04 MAR 2210
Nuku'Alofa            TONGA         21.10S  175.20W  0.06        04 MAR 2115
Suva Viti Levu        FIJI          18.10S  178.42E  0.13        04 MAR 2200
Rarotonga Wharf       COOK ISLAND   21.20S  159.79W  0.08        04 MAR 2200
Kaingaroa Chatham Is  PACIFIC OCEA  43.70S  176.27W  0.22        04 MAR 2320
Norfolk Island.       AUSTRALIA     29.10S  167.95E  0.64        04 MAR 2245
Port Villa            VANUATU       17.80S  168.31E  0.32        04 MAR 2320
Ouinne                NEW CALEDONI  22.00S  166.83E  0.2         04 MAR 2320
Tubuai                FRENCH POLYN  23.30S  149.48W  0.06        04 MAR 2305
Port Kembla           AUSTRALIA     34.50S  151.00E  0.15        05 MAR 0205
Mare                  NEW CALEDONI                   0.15        04 MAR 2330
North Cape            NEW ZEALAND                    0.15        04 MAR 2130
Great Barrier Island  NEW ZEALAND                    0.20        04 MAR 2240

See also [1], [2] & [3]

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  • $\begingroup$ Wow, thank you for such a data-laden and sourced answer! Are these heights in deep water or shallow? My guess is that they are fairly close to land but I can't figure out where the sea level gauges are listed on that site nor where these heights come from. The depth has a substantial effect on how the wave evolves. $\endgroup$ – uhoh Mar 5 at 23:47
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    $\begingroup$ Washington Post: Here’s why Thursday’s earthquakes didn’t trigger a damaging Pacific tsunami $\endgroup$ – uhoh Mar 6 at 4:40
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    $\begingroup$ What a difference one order of magnitude makes when it comes to earthquakes. I initially thought the 2011 quake that resulted in the Fukushima tsunami was a small magnitude quake, but it was 9.0-9.1. $\endgroup$ – Fred Mar 6 at 14:01

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