The struck the Kantō Plain on the main Japanese island of Honshū at 11:58:44 JST (02:58:44 UTC) on Saturday, September 1, 1923. Varied accounts indicate the duration of the earthquake was between four and ten minutes. Extensive firestorms and even a fire whirl added to the death toll. The Kantō Massacre began on the day of the earthquake. The earthquake had a magnitude of 7.9 on the moment magnitude scale (), with its focus deep beneath Izu Ōshima Island in Sagami Bay. The cause was a rupture of part of the convergent boundary where the Philippine Sea Plate is subducting beneath the Okhotsk Plate along the line of the Sagami Trough. Since 1960, September 1 has been designated by the Japanese government as , or a day in remembrance of and to prepare for major natural disasters including tsunami and typhoons. Drills, as well as knowledge promotion events, are centered around that date as well as awards ceremonies for people of merit. Earthquake The SS Dongola captain reported that, while he was anchored in Yokohama's inner harbor: This earthquake devastated Tokyo, the port city of Yokohama, and the surrounding prefectures of Chiba, Kanagawa, and Shizuoka, and caused widespread damage throughout the Kantō region. The earthquake's force was so great that in Kamakura, over from the epicenter, it moved the Great Buddha statue, which weighs about 121 tonnes, almost 60 centimeters. Estimated casualties totaled about 142,800 deaths, including about 40,000 who went missing and were presumed dead. According to the Japanese construction company Kajima Kobori Research's conclusive report of September 2004, 105,385 deaths were confirmed in the 1923 quake. The damage from this natural disaster was one of the greatest sustained by Imperial Japan. In 1960, on the 37th anniversary of the quake, the government declared September 1 an annual "Disaster Prevention Day". Damage and deaths Because the earthquake struck when people were cooking meals, many were killed as a result of large fires that broke out. Fires started immediately after the earthquake. Some fires developed into firestorms that swept across cities. Many people died when their feet became stuck on melting tarmac. The single greatest loss of life was caused by a fire whirl that engulfed the Rikugun Honjo Hifukusho (formerly the Army Clothing Depot) in downtown Tokyo, where about 38,000 people were incinerated after taking shelter there after the earthquake. The earthquake broke water mains all over the city,