Not that it's much use to compare, but the closest DART buoy 21418 to the M9-9.1 2011 Tōhoku earthquake[1] (which had an epicentre just 72km East of Japan's east coast) recorded a water column height variation of ~3m.[2][3] The closest DART buoy to today's M8.7-8.8 earthquake is 21416 and this recorded a water column height variation of ~0.6m back in the M9-9.1 2011 Tōhoku earthquake.[4]

[1] https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_an...

[2] https://www.ngdc.noaa.gov/hazard/data/DART/20110311_honshu/j...

[3] https://www.ngdc.noaa.gov/hazard/dart/2011honshu_dart.html

[4] https://www.ngdc.noaa.gov/hazard/data/DART/20110311_honshu/j...