印度洋8.7级特大地震后川滇地区地震活动趋势判定

2004年12月26日发生了印尼Ms8．7特大地震，我国川滇地区震时和震后有明显响应，如小震活动加强、流体各种前兆异常突出等。为了判定我国大陆地震活动的趋势，2005年1月对川滇地区进行了紧急GPS应急加测。此前，中国地壳运动观测网络分别于1999、2001、2004年进行了三期GPS复测。在这三期复测资料的基础上，对此次紧急复测资料和相关的几个GPS连续观测站的资料进行了分析，认为：①川滇地区的地壳形变主要为机械形变所致，且在8．7级地震震时和震后呈相对松驰变化，这有利于短期内5～6级地震的发生；②若大幅度压缩与拉张反复交替出现，也不排除孕育更强地震的可能性。

Estimation of the Earthquake Situations in the Sichuan-Yunnan Area after the MS8.7 Great Earthquake in the Indian Ocean

On 26 Dec.2004,in Indonesia occurred a great earthquake with M_S8.7.During and after that,a series of anomalies appeared in Yunnan and Sichuan of China,such as earthquake activity intensifying,obvious subsurface fluid anomalies, etc.In order to judge the earthquake situations in the area,an urgent GPS measurement was carried out during Jan.to Feb.of 2005.Based on the data of this time and former three times of GPS measurements in 1999,2001 and 2004 as well as the data from a few concerned continuous observation stations,we think:(1) the crust deformation in Yunnan and Sichuan is induced mainly by mechanic vibration,and it shows a relatively loosensing change during and after the earthquake,which is favorable to trigger the earthquake with M_S5-6 in a short period;(2) if large-amplituded compressive and extensional variations appear alternately,stronger earthquake can still happen in this area.