青藏高原东北缘近期重力与地壳形变综合分析与研究

发布时间：2018-09-01 17:14

【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。
[Abstract]:Based on the observational data of mobile gravity and GPS in the northeastern margin of the Qinghai-Xizang Plateau during 2011-2014 and the background data of vertical motion obtained from the leveling observations from 1970 to 2011, combined with the regional tectonic dynamic environment and the strong earthquake events occurring in the region, The relationship between regional gravity field variation, crustal 3D deformation and regional tectonic environment and strong earthquake activity is systematically analyzed. The temporal and spatial distribution characteristics and mechanism of regional gravity field variation and regional 3D crustal movement are further studied and discussed. The results show that the variation of gravity field in the measured area is closely related to the horizontal motion reflected by GPS observation and the vertical motion reflected by leveling observation. The crustal deformation generally shows an increase in gravity along the direction of horizontal movement, and a compression uplift in the plateau mountainous area. The decrease of surface gravity, the relative extension and subsidence of faulted basins and the increase of surface gravity reflect the succession of neotectonic activities (.2) the crustal deformation field changes are closely related to active faults. The trend of gravity variation and vertical deformation isoline is basically consistent with that of Qilian Haiyuan fault in NWW direction. The horizontal deformation also produces an obvious left-lateral strike-slip movement near the Qilian Haiyuan fault. 3) strong earthquakes tend to occur in active fault zones with significant gravity variation. It is also prone to occur where the vertical differential movement of fault blocks along active faults is strong or both strong strike-slip movements. The regional crustal deformation near the epicenter of the Menyuan earthquake in 2016 is obvious. The characteristics of surface compressibility and gravity change are the most obvious. The 2013 Minxian Zhangxian earthquake of magnitude 6.6 occurred in the area where the gravity variation gradient belt is turning. The first author of this paper has made a certain degree of medium-term prediction before the Minxian Mengyuan earthquake based on the crustal deformation data in Minxian, especially the site prediction. Based on the above understanding, it is emphasized that there may still be a medium and long term strong earthquake / strong earthquake hazard background in some anomalous parts of crustal deformation formed in the study area.
【作者单位】：中国地震局第二监测中心;
【基金】：国家自然科学基金(41274083,61627824) 中国地震局地震行业科研专项(201508009)共同资助
【分类号】：P315.72

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