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Japan study disproves notion that appearances of deep-sea fish augur big earthquakes

A giant oarfish measuring around 5 meters in length is seen after being caught in a fixed net at Wakasa Bay, in Tai Fishing Harbor in Miyazu, Kyoto Prefecture, on Jan. 11, 2018. (Mainichi/Hiroki Abe)

TOKYO -- A Japanese research team says it has disproved the long held notion that appearances of deep-sea fish in shallow waters are a harbinger for big earthquakes.

The team consisting of researchers from Tokai University and the University of Shizuoka analyzed 221 large earthquakes up to the March 2011 Great East Japan Earthquake to reach their conclusion. Yoshiaki Orihara, specially appointed associate professor of solid earth geophysics at Tokai University, said, "The belief is not helpful information for disaster prevention."

In examining the notion, the team looked at the appearances of eight kinds of deep-sea fish said to portend earthquakes. These included the giant oarfish, a red dorsal-finned vibrant silver fish that can measure 4 meters in length, and the big-eyed, slender ribbonfish, which looks like a beltfish.

The 221 earthquakes recorded as magnitude 6 or greater between 1928 and 2011 were compared against 336 cases in which the fish were reported in newspaper articles and other sources as having been caught or washed up on the shore over the same period.

The team found only one occurrence of a strong earthquake taking place within 30 days and inside a 100 kilometer radius of one of the fish's appearances -- around the time of the 2007 Niigata-Chuetsu Offshore Earthquake. The result led the team to conclude that the long-held belief is just a superstition.

Strange observable natural phenomena and irregular behavior from animals in the run-up to a powerful earthquake is said to be explained as "earthquake weather." In Japan, the connection with deep sea fish reportedly first appeared during the Edo period (1603-1868), in a collection of strange tales titled "Shokoku Rijin Dan."

Orihara said, "We began our research thinking that the appearance of deep sea fish could become supplementary information for disaster prevention, but now we know that's not the case. There's no need for alarm if one appears. Knowing that it is difficult to predict earthquakes, we want people to be prepared in their daily lives."

The results of the team's study were published in the Bulletin of the Seismological Society of America.

(Japanese original by Mayumi Nobuta, Science & Environment News Department)

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