Abstract: In this study, we systematically analyzed the relationship between regional gravity changes, 3D crustal deformation, regional tectonic environment and strong earthquakes based on the relative gravity measurements(2011-2014), GPS data and the background vertical deformation from the leveling measurements conducted from 1970 to 2011. Subsequently, we further characterized the temporal-spatial patterns and discussed the mechanism of regional gravity changes and the crustal deformation. The results can be summarized as follows:1)The regional gravity changes, the GPS-derived horizontal deformation and the vertical deformational obtained from leveling data showed a close spatial relationship:The gravity increased along with the direction of horizontal movement, and the gravity decreased with the crustal uplift and vice versa, which reflects the inherited characteristics of neotectonic activities. 2)The crustal deformation was closely related to the active faults. The contour lines of gravity changes and vertical deformation were generally along with the Qilian-Haiyuan Fault(the strike is NWW), and the crustal horizontal deformation showed left-lateral strike slip motion near the Qilian-Haiyuan Fault. 3)The strong earthquakes usually occur in the active faults where intensive gravity change and vertical and/or horizontal deformation occurred. The extrusion deformation, surface compression rate and gravity changes were obvious near the epicenter of 2016 Menyuan earthquake. The 2013 Minxian-Zhangxian M_S6.6 earthquake occurred in the direction-turning area of intense gravity gradient zone and the transitional area of surface compression and vertical deformation. The first author of this paper has made a medium-term forecast before the Minxian and Menyuan earthquakes, especially the location of the earthquake. Based on the above understandings, we emphasized that:there are still possibilities of strong or huge earthquakes within medium-long term in the areas of crustal deformation anomalies in the study region.

Key words: northeastern edge of the Tibetan plateau, gravity change, GPS, leveling measurement, tectonic activity

摘要： 利用青藏高原东北缘2011-2014年期间的流动重力与GPS观测资料和1970-2011年水准观测获得的垂直运动背景场资料，结合区域地质构造动力环境和区内发生的强震事件，系统分析了区域重力场变化、地壳三维形变与区域构造环境和强震活动的关系，进一步研究和探讨了区域重力场变化与区域三维地壳运动的时空分布特征及其机理。结果表明：1）测区内重力场变化与GPS观测反映的水平运动和水准观测反映的垂直运动在空间上关系密切，地壳形变总体表现为沿水平运动的方向重力增加，高原山地挤压隆升，地面重力减少；断陷盆地相对伸展下沉，地面重力增加，反映了新构造活动的继承性。2）地壳形变场变化与活动断裂密切相关，重力变化和垂直形变等值线走向总体上与呈NWW向的祁连-海原断裂走向基本一致，水平形变也在祁连-海原断裂附近产生明显的左旋走滑运动。3）强震易发生在具有显著重力变化的活动断裂带上，也易发生在沿活动性断裂的断块垂直差异运动强烈或兼有强走滑运动的地方。2016年门源震中附近区域地壳受挤压变形显著、面压缩率和重力剧烈变化的特征最为显著。2013年岷县漳县6.6级地震发生在重力变化高梯度带拐弯的地区，也是面压缩率变化过渡带和垂直形变过渡带地区。4）文中第一作者等曾基于该区地壳形变资料在岷县、门源地震前做过一定程度的中期预测，尤其是地点预测。基于上述认识，进而强调在研究区形成的一些地壳形变异常部位可能仍存在中长期强震/大震危险背景。

关键词: 青藏高原东北缘, 重力变化, GPS, 水准测量, 构造活动