日本地震导致地球自转加快英文材料.doc

JapanQuake Shortens Earth Day Japans devastating 9.0?magnitude earthquake last Friday was so powerful that experts say it slightly increased the Earths rotation speed, making the day a fraction of a second shorter. U.S. space agency scientist Richard Gross said the quake shifted the way the Earths mass is distributed, which made the planet spin a little faster, cutting the 24-hour day by an estimated 1.8 microseconds. That is less tha n two milli on ths of one second. The scenario is like that of a figure skater who draws her arms into her body during a spin, in order to turn faster on the ice. The shift in the earths mass was also seen in surface changes to the Japanese coastline, caused by the sudden slippage of colliding plates of the earths crust far below? Global positioning stations closest to the epicenter moved eastward by up to 4 meters during the quake. Last years 8.8? mag nitude earthquake in Chile, and the 9.1 -magnitude quake that struck Ind on esia in 2004 each cut several microseco nds from the length of the Earths day? It is normal for the length of a day on Earth to vary by about 1.000 microseconds (one millisecond) throughout the year. The U.S. Geological Survey says the earthquake in Japan was the worlds fifth-largest since 1900.