LAUSR

The 4 May 2018 (Mw 6.9) earthquake offshore of Kilauea Volcano has raised concerns about potential impacts of locally generated tsunamis in Hawaii. Iterative inversion of global seismic observations guided by forward modeling of regional geodetic and tsunami records yields a self-consistent fault slip model to quantify the physical processes. This earthquake, similar to other large events in the area, is found to involve a shallowly dipping thrust fault, plausibly on the décollement between the island volcanic edifice and the old Pacific seafloor. The uplift and seaward displacement of Kilauea’s south flank generate a tsunami that wraps around Hawaii Island, exposing all shores to direct arrivals and the interconnected insular shelves to resonating wave activities. The impact along the Hawaiian Islands can be categorized at three regional levels in terms of peak wave amplitude and arrival time with implications for tsunami hazards from future larger earthquakes and flank failures. Plain Language Summary On 4May 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. The short time before the tsunami arrival prompted concerns about response planning for potential larger earthquakes on Kilauea’s flank. A model of the earthquake rupture is determined using teleseismic waves, geodetic records, and tsunami observations. Numerical modeling of the tsunami propagation along the island chain reveals coastal regions with severe, moderate, and minor impact. The earthquake parameters, rupture extent, and tsunami impact from this study are useful for local tsunami hazard assessment and mitigation.