The orphan Sanriku tsunami of 1586: new evidence from coral dating on Kaua‘i

We have re-examined the historical evidence in the circum-Pacific for the origin of the 1586 orphan tsunami of Sanriku, Japan, previously attributed to a Lima, Peru, earthquake and tsunami in 1586. New evidence comes from corals found in a unique paleotsunami deposit on Kaua‘i. Dated by 230 Th- 238 U geochronology these corals determine an absolute age in high precision of a Pacific tsunami event that was previously dated to approximately the sixteenth century by 14 C methodology. Detrital corrected ages of three low thorium, well-preserved coral clasts range from 415 to 464 years old (relative to 2016), with a mean age of 444 years ±21 (\( 2\sigma_{{\bar{X}}} \)). Literature evidence for circum-Pacific paleotsunami in this time range is reviewed in light of the new high-precision dating results. Modeled and observed tsunami wave amplitudes in Japan from several Peruvian events are insufficient to match the 1586 Sanriku observation, and paleodated earthquakes from Cascadia, the Alaskan Kodiak region, and Kamchatka are incompatible with the Sanriku data in several ways. However, a mega-earthquake (M w > 9.25) in the Aleutians is consistent with the Kaua‘i evidence, Pacific Northwest observations, and the Sanriku tsunami amplitude. The Kaua‘i coral paleotsunami evidence therefore supports the origin of the 1586 Sanriku tsunami in the Aleutian Islands.