WASHINGTON - China's Sichuan earthquake of May 12 occurred as the result of motion on a northeast striking reverse fault on the northwestern margin of the Sichuan Basin, the United States Geological Survey (USGS) said on Monday.

The earthquake's epicenter and focal-mechanism are consistent with it having occurred as the result of movement on the Longmenshan fault or a tectonically related fault, said the USGS.

On a continental scale, the seismicity of central and eastern Asia is a result of northward convergence of the India plate against the Eurasia plate with a velocity of about 50 millimeter per year.

The convergence of the two plates is broadly accommodated by the uplift of the Asian highlands and by the motion of crustal material to the east away from the uplifted Tibetan Plateau.

The 7.8-magnitude quake jolted Wenchuan County of China's southwestern Sichuan province at 2:28 pm (0628 GMT) Monday, claiming thousands of lives in eight affected provinces and municipalities.

词汇提示：

1. reverse fault 逆断层
2. United States Geological Survey 美国地质调查局
3. epicenter 震中
4. focal-mechanism 震源机构
5. seismicity 地震活动

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