Mechanism of the 4 May 2018 East Hawaiian Earthquake and Tsunami: Evidence of Progressive Volcanic Flank Failure?

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Large earthquakes occur at boundary of the volcanic edifice and the old Pacific Plate in the Hawaii islands. These earthquakes, including the 1868 M8.0 Kau, Hawaii and the 1975 M_w7.7 Kalapana earthquake also generated large tsunamis that caused serious damage and casualties. However, the mechanism of these tsunamis is not well understood. Previous research postulated that the 1975 tsunami was triggered by the combination of faulting and slumping of the weak volcanic flank caused by strong shaking. In this study, we focus on the most recent 4 May 2018 M_w6.9 Kilauea, Hawaii earthquake and its tsunami to understand whether the anomalous tsunamis of these can be explained by ongoing flank collapse.

Thirty-one near-field GPS data and nine strong motion data are used to jointly invert for a source model of the 2018 M_w6.9 earthquake. We then forward model the coseismic seafloor deformation and the ensuing tsunami. Our preliminary results from the joint inversion show that the earthquake-driven component cannot explain the tsunami records completely. This discrepancy is further analyzed by carrying out a tsunami ray tracing analysis, where an additional far-field tide gauge and a Deep-ocean Assessment and Reporting of Tsunami (DART) buoy data are used to constraint the location of the tsunami source using the measured travel times. This suggests that the tsunami is likely, at least in part, driven by a coseismic landslide.

The mechanism of submarine landsliding in Hawaii is of broad interest for the natural hazards community. Geologic evidence shows that at least 15 large landslides associated with volcanic processes have generated megatsunamis with interpreted run up as large as 300 m. Tsunamis in the Hawaiian Islands can cause widespread devastation, so our understanding of the 2018 M_w6.9 earthquake, its tsunami, and the relationship between different tsunamigenic sources is important for understanding and quantifying tsunami hazards in Hawaii.

Presenting Author: Jiun-Ting Lin

Authors