川滇地区重力场动态变化及其强震危险含义  

Dynamic variation of the gravity field in the Sichuan-Yunnan region and its implication for seismic risk

作　　者：祝意青[1] 刘芳[1] 李铁明[2] 郑兵[3] 王青华[4] 

机构地区：[1]中国地震局第二监测中心,西安710054 [2]中国地震局地质研究所,北京100029 [3]四川省地震局测绘工程院,四川雅安625000 [4]云南省地震局,昆明650224

出　　处：《地球物理学报》2015年第11期4187-4196,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41274083;41374026);陕西省科技计划项目(2014K13-04);地震行业科研专项(201508009)资助

摘　　要：基于川滇地区2011—2014年的重力复测资料,系统分析了区域重力场时-空动态变化及其与2012年云南彝良MS5.7、2013年四川芦山MS7.0、2014年云南鲁甸MS6.5和四川康定MS6.3地震发生的关系.结合GPS、水准观测成果和区域地质构造动力环境,进一步研究了区域重力场变化的时空分布特征及其机理,讨论了近期区域重力场动态变化的强震危险含义.结果表明:1重力变化与川滇地区断裂构造活动存在密切空间联系,重力变化较好地反映了伴随活动断层的物质迁移和构造变形引起的地表重力变化效应.2重力资料对测区内2012年以来发生的4次MS5.7以上强震均有较好反映,地震前震中区及其附近观测到明显的区域性重力异常及重力变化高梯度带,可能是地震孕育过程中观测到的重力前兆信息.3区域重力场动态演化大体反映了青藏高原物质东流的动态效应,龙门山断裂带地壳受挤压隆起、面压缩率和重力上升变化的特征最为显著.4重力场的空间分布及其随时间变化与地壳垂直与水平运动及地质构造活动等观测结果有一定的对应关系,强震易发生在重力变化四象限分布中心地带或正、负异常区过渡的高梯度带上,研究区的一些重力异常部位仍存在中-长期大震危险背景.Using the gravity remeasurement data from 2011 to 2014in the Sichuan-Yunnan region,we have systematically analyzed the spatial-temporal variations of the regional gravity field and their relation to the occurrence of the Yiliang MS5.7earthquake in 2012,Lushan MS7.0earthquake in2013,Ludian MS6.5earthquake and Kangding MS6.3earthquake in 2014.Combined with GPS data and leveling observations and regional geologic structure,the time-space distribution of the gravity field and its mechanism were further studied,and its implication for seismic risk is discussed.The interannual variation of gravity dynamic change in the Sichuan-Yunnan region during2011 to 2012,2012 to 2013,2013 to 2014and the accumulation change during 2011 to 2014are analyzed.And we have discussed the evolution characters of the gravity field.Combined with regional gravity field variation and seismic activity,and with GPS data during 2011 to 2014,and leveling data during 1971 to 2011,we have found the relationship between strong earthquake and gravity variation in recent years.And on this basis,combined with regional geology structure,we further assess the seismic risk in the Sichuan-Yunnan region in the future.The results show that gravity variation is closely linked with the fault activity in the SichuanYunnan region.It is caused by material migration accompanying active faulting and crustal tectonic motion.The gravity data from the survey area since 2012 have obvious response to four major earthquakes（MS5.7）.Regional gravity anomalies and a gravity gradient change may be a seismic precursor.Dynamic evolution characteristics of the gravitational field roughly reflects the dynamic effects of the moving material of the Tibetan plateau which spread toward east and the Longmenshan fault zone by the crust uplift,where compression rates and gravity change are most significant.The spatial distribution of the gravity field and its changes over time and vertical and horizontal crustal movement and tectonic activity observations have certain corresponding

关 键 词：川滇地区 重力场变化 构造活动 芦山地震 鲁甸地震 中-长期地震危险背景 

分 类 号：P312[天文地球—固体地球物理学] P315[天文地球—地球物理学]