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| Date | December 20, 1946 |
|---|---|
| Magnitude | 8.1 Mw[1] |
| Epicenter location: | [2] |
| Countries/ regions affected |
 Japan |
| Tsunami: | Yes |
| Casualties: | At least 1362 dead, 2600 injured and 100 missing[1] |
The 1946 Nankaidō earthquake was a major earthquake in Nankaidō, Japan. It occurred on December 20, 1946 at 19:19 UTC.[1] The earthquake was gigantic, measuring 8.1 on the moment magnitude scale, and was felt from Northern Honshū to Kyūshū.[1]
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The 1946 Nankaido earthquake occurred in the Nankai Trough, a highly active, vigorous, subduction zone where large earthquakes have been recorded since the seventh century, with a recurrence time of 100 to 200 years.[3]
The 1946 Nankaido earthquake was unusual in its geographical perspective, with a rupture zone estimated from long-period geodetic data that was more than twice as large as that derived from shorter period seismic data. In the center of this earthquake rupture zone, scientists used densely deployed ocean bottom seismographs to detect a subducted seamount 13 kilometers (8 mi) thick by 50 kilometers (31 mi) wide at a depth of 10 kilometers (6 mi). Scientists propose that this seamount might work as a barrier inhibiting brittle seismogenic rupture.[3]
The earthquake caused extensive damage, eventually destroying 36,000 homes in southern Honshu alone.[1] The earthquake also caused a huge tsunami that took out another 2,100 homes with its 5-6 meter (16-20 feet) waves.[1] Landslides, ground fissures, uplift and subsidence were observed in the epicenter's area.[1]