Tanaka-shown here on the coast at Shizuoka-and her colleagues found that three-quarters occurred when tides were very large, more than six feet (two meters) over the mean sea level.

• 田中（图中这名坐在静冈某海岸的女性）和她的同事发现有四分之三的地震发生在大潮的时候，海浪的高度高出平均海平面超过两公尺高。