1923 Great Kantō earthquake collapsed due to urbanization. The 1923 earthquake led to record-high morbidity due to unsanitary conditions following the earthquake, and it prompted the establishment of antityphoid measures and the building of urban infrastructure. The Honda Point Disaster on the United States west coast, in which seven US Navy destroyers ran aground and 23 lives were lost, has been attributed to navigational errors caused by unusual currents set up by the earthquake in Japan. Beginning in 1960, every September 1 is designated as Disaster Prevention Day to commemorate the earthquake and remind people of the importance of preparedness, as August and September
2011 Tōhoku earthquake and tsunami intensities were smaller than the actual ones in some places, especially in Kanto, Koshinetsu, and Northern Tōhoku regions where the populace warning did not trigger. According to the JMA , reasons for the underestimation include a saturated magnitude scale when using maximum amplitude as input, failure to fully take into account the area of the hypocenter, and the initial amplitude of the earthquake being less than that which would be predicted by an empirical relationship. There were also cases where large differences between estimated intensities by the Earthquake Early Warning system and the actual intensities occurred in the aftershocks and