A reader notes that in Tsunami Insurance I wrote that “...it appears that insurers usually exclude tsunamis from flood coverage, considering them more like earthquakes." (Note the words “it appears that".)
He says he has researched this issue and has found that:
In the US, the National Flood Insurance Plan (NFIP), the Insurance Services Office (ISO) and the Factory Mutual Insurance Company (FMO) consider all forms of wave damage including tsunamis and tidal waves as flood losses. These groups are not concerned with what caused the flood.
That paragraph is from a report Perspectives -- Tsunami by the insurance broker Willis; look under January 28, 2005. The report has much further context, including a discussion of how nonetheless many insurers may write policies that make an excluded peril take precedence over an insured peril.
He also notes some insurers that do class tsunamis as earthquakes, as I mentioned.
Among the many possible causes of tsunamis, ranging from mudslides to meteors, it seems that people living in places that might have tsunamis (which includes the North American east coast) might do well to check their insurance policies, especially for flood insurance, to see what sort of concurrent contingent perils may be included in them.