May 4, 2018 Tsunami: Hawaii, United States

Pacific Tsunami Warning Center director Dr. Charles "Chip" McCreery said that a magnitude 6.9 is normally the minimum threshold that a tsunami warning would be issued. However, for this earthquake, PTWC initially estimated it at a smaller magnitude, so they issued an information statement instead. The information statement said there was no tsunami threat from the earthquake. Later analysis did boost the magnitude to 6.9, but by that time PTWC already had sea level measurements and knew there was no tsunami threat and didn't have to upgrade to a warning level at that point. There was no threat of a tsunami, but a small tsunami was generated. McCreery said it you were at the coast, you would have seen the water level slowly go up and down. The wave was a little over a foot above normal sea level at Kapoho, where PTWC have the closest gauge to where the earthquake happened. (reference #12124)

On 4 May 2018, early in the 2018 Kilauea volcanic eruption sequence, an Mw 6.9 earthquake ruptured the south flank of Hawaii Island. The event involved seaward sliding of a wedge of the island offshore of the East Rift Zone, likely on the contact surface between the island and the Pacific Ocean seafloor. The resulting motion generated a modest tsunami that arrived on the shores of the major Hawaiian Islands in less than an hour. (reference #12263)