Citation

Fukao Y, Sandanbata O, Sugioka H, Ito A, Shiobara H, Watada S, Satake K. Sci. Adv. 2018; 4(4): eaao0219.

Affiliation

Earthquake Research Institute, University of Tokyo, Tokyo, Japan.

Copyright

(Copyright © 2018, American Association for the Advancement of Science)

DOI

10.1126/sciadv.aao0219

PMID

29740604

PMCID

PMC5938283

Abstract

Tsunami earthquakes are a group of enigmatic earthquakes generating disproportionally large tsunamis relative to seismic magnitude. These events occur most typically near deep-sea trenches. Tsunami earthquakes occurring approximately every 10 years near Torishima on the Izu-Bonin arc are another example. Seismic and tsunami waves from the 2015 event [M_w (moment magnitude) = 5.7] were recorded by an offshore seafloor array of 10 pressure gauges, ~100 km away from the epicenter. We made an array analysis of dispersive tsunamis to locate the tsunami source within the submarine Smith Caldera. The tsunami simulation from a large caldera-floor uplift of ~1.5 m with a small peripheral depression yielded waveforms remarkably similar to the observations. The estimated central uplift, 1.5 m, is ~20 times larger than that inferred from the seismologically determined non-double-couple source. Thus, the tsunami observation is not compatible with the published seismic source model taken at face value. However, given the indeterminacy of M_zx, M_zy, and M_{tensile} of a shallow moment tensor source, it may be possible to find a source mechanism with efficient tsunami but inefficient seismic radiation that can satisfactorily explain both the tsunami and seismic observations, but this question remains unresolved.

Language: en