Kobe Design University, Nishi-ku, Kobe, Hyogo 651-2196, Japan
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(Received January 11, 2012; Accepted January 23, 2012)
Abstract. A hypothesis is proposed to understand an unusually large shift of the sea bottom (24 m) in the recent Tohoku- Kitakanto Earthquake, which means the suppression of the slip at the contact surface of the North American and the Pacific plates for about 300 years. The key point of the hypothesis is the effect of the global warming, which has melted the ice on the northern part of the North American plate (Greenland and Canada). It changed the gravity distribution of the plate, and the plate tilted so that the North American plate covering the northern part of Japan began to press the Pacific plate downwards. A simple experiment was made to observe this plate motion. Records of past earthquakes in the eastern Asia are compared to the climate change, where the sun-spot numbers are used as a measure of mean temperature.
Keywords: Earthquake, Plate Motion, Shift of Sea Bottom, Buoyancy of Plate, Global Warming