中文摘要：

利用川滇地区不同时-空尺度的重力复测资料,系统分析了区域重力场时-空动态变化及其与2014年云南鲁甸MS6.5、2013年四川芦山MS7.0和2008年四川汶川MS8.0地震发生的关系。结果表明：1）强震发生前,重力场出现较大空间范围的区域性重力异常及与测区主要断裂构造带走向基本一致的重力变化高梯度带,可能反映地震前区域应力场的增强及沿主要断裂带在地震孕育发生期间发生了引起地表重力变化效应的构造活动或变形;2）多时-空尺度的重力场动态变化图像均出现较显著的相对重力异常变化,随着累计时间的增长,重力变化更为显著,可视为强震的中期前兆信息,强震主要发生在重力场变化分布差异较为剧烈的地区;3）重力场动态变化对强震的地点预测具有重要指示作用,大区域重力网能较好地判断强震主体地区,时-空分辨率较高的省局区域重力网能较好地判定强震发震地点,为更好地判定强震发震位置,则需要相应的更密集的观测网点控制;4）文章第一作者在汶川、芦山、鲁甸地震前的中期预测尤其是地点预测均取得较好成效。基于上述认识,进而强调在研究区形成的一些重力变化异常部位可能仍存在大震中-长期危险背景,需继续加强监视。

英文摘要：

Using the multiple-scale campaign gravity data in Sichuan-Yunnan area, we systematically analyzed the relationships between the spatial-temporal gravity changes and the 2014 Ludian,Yunnan Province MS6. 5 earthquake and the 2013 Lushan MS7. 0 and the 2008 Wenchuan MS8. 0 earthquakes in Sichuan Province. Our main results are as follows. 1） Before the occurrence of great earthquakes,gravity anomalies occurred in large area around the epicenters. The directions of gravity change gradient belts usually agree roughly with the directions of the main fault zones of the study area. Such gravity changes might reflect the increase of crustal stress,as well as the significant active tectonic movements and surface deformations along fault zones, during the period of gestation of great earthquakes; 2） The continuous significant changes of the multiple-scale gravity fields,as well as the greater gravity changes with larger time scales,can be regarded as the medium-range precursors of great earthquakes. The subsequent great earthquakes always occur at the area where the gravities change greatly; 3） The spatial-temporal gravity changes are much useful in determining the epicenter of the coming great earthquakes. The large gravity networks are useful in determining the major areas of the coming great earthquakes. However,the local gravity networks with high spatial-temporal resolution are suitable for determining the location of epicenters. Therefore,denser gravity observation networks are necessary for better forecasting the epicenters of great earthquakes. 4） Using gravity changes from campaign observation data,the first author of this paper had made medium-range predictions to the 2004 Ludian MS6. 5, 2013 Lushan MS7. 0 and 2008 Wenchuan MS8. 0earthquakes,specially,the successful predictions of the location of epicenters. Based on above discussions,we emphasize that the medium / long-term potential of great earthquakes might exist nowadays in some areas with significant gravity anomalies in the study region. Because of t