The , was the third Ansei Great Earthquake, which occurred during the late-Edo period. It occurred after the 1854 Nankai earthquake, which took place about a year prior. The earthquake occurred at 22:00 local time on 11 November. It had an epicenter close to Edo (now Tokyo), causing considerable damage in the Kantō region from the shaking and subsequent fires, with a death toll of 7,000–10,000 people and destroyed around 14,000 buildings. The earthquake had a magnitude of 7.0 on the surface wave magnitude scale and reached a maximum intensity of XI (Extreme) on the Mercalli intensity scale. The earthquake triggered a minor tsunami. Tectonic setting The Kanto area lies above a complex part of the convergent boundaries between the subducting Pacific and Philippine Sea Plates and the overriding Eurasian and North American Plates. Earthquakes with epicenters in the Kantō region may occur within the Eurasian Plate, at the Eurasian Plate/Philippine Sea Plate interface, within the Philippine Sea Plate, at the Philippine Sea Plate/North American Plate interface (under the Sagami Trough), at the Philippine Sea Plate/Pacific Plate interface (Izu–Bonin–Mariana Arc), or within the Pacific Plate. In addition to this set of major plates it has been suggested that there is also a separate 25 km thick, 100 km wide body, a fragment of Pacific Plate lithosphere. The cause of the 1855 earthquake is unknown; it is consistent with a rupture along the interface between the Eurasian and Philippine Sea Plates, adjacent to, and down dip from, the rupture that caused the 1923 Great Kantō earthquake. Damage A total of about 50,000 houses and over 50 temples were either destroyed by the earthquake shaking or subsequent fires. An area of about 2.3 km2 was burned down in Edo (now Tokyo). The earthquake's destruction and associated death toll were especially great for the time, as Ansei Edo was composed largely of plaster-and-tile structures that were resistant to fires but prone to tremors. In spite of Japan's long history with earthquakes, as of 1855 Edo had not experienced a major quake for about 154 years; in the minds of the citizenry, earthquakes were either a thing of the past or simply too unlikely to reasonably plan for. This lack of structural preparation, combined with the fact that most of the well-populated areas of Edo were built on former wetlands artificially filled in with unstable alluvial soil, left the city undefended from the massive