a sign of a major earthquake in Japan

(1)Signs of a major earthquake in Japan: More than 30 dolphins die in droves, raising anxiety
(2)Fifty-four dolphins died seven days before the Great East Japan Earthquake
(3)Seoul = News 1 Reporter Kim Ye-seul Sent 2023-04-101035
(4)More than 30 dolphins have died on the coast of Japan, raising fears that it could be a precursor to a major earthquakeNHK Broadcasting Corporation’s “Galmuri.”
(5)More than 30 dolphins have died on the coast of Japan, raising fears that it could be a precursor to a major earthquake
(6)According to Japanese current affairs weekly Shukangendai and NHK on the 10th, 32 stone rings were stranded on the coast near Ichinomiya-cho, Chiba Prefecture, Japan on the 3rd, of which 15 were reported to have died