中国大陆重力场时变监测与强震预测

Time-varying Gravity Field Monitoring and Strong Earthquake Prediction on the Chinese Mainland

主要回顾了中国大陆重力时变高精度监测与地震预测应用的基本情况。自1966年邢台地震以来,我国就开始采用重力手段监测地壳变动和强震孕育发生过程,致力获取重力场时变的微伽级信息。重力监测主要采用定点流动复测(流动重力)和固定台站连续观测(连续重力)2种方式。重力监测已经历3个发展阶段。1998年以前,重力监测主要沿块体边界、活动断层或历史强震区开展,缺乏绝对测量,一般采用相对测量,通过总结获取了海城7.2级、唐山7.8级、丽江7.0级等一系列地震前的重力动态变化特征,除海城地震外,预测成功震例寥寥。1998年地壳运动网络工程建设以来,由于引入高精度绝对重力测量,开始进行中国大陆重力场的整体监测,获取了汶川8.0级等地震前的大尺度变化信息,给出了汶川地震中期预测的有效意见。2010年以来,以陆态网络工程重力网为基础,逐步开展大华北、南北带等各种测网的整合与统一,形成了中国大陆整体重力观测网,对期间发生的一系列6.0级以上地震(如芦山7.0级、门源6.4级、呼图壁6.2级等地震)进行了较为成功的中期预测,为地震机理研究和我国中期地震预测水平提升发挥了重要作用。通过长期的重力观测实践,初步形成了一门专门应用于地震研究的交叉学科——"地震重力学"。

The basic situation of monitoring the high precision time-varying gravity field and the application of earthquake prediction in Chinese mainland is reviewed.Since the Xingtai earthquake occurred in 1966,gravity field,especially the micro-gal level information of the time-varying gravity field,started to be applied to monitor the crustal movement and the process of strong earthquake in China.In general,gravity monitoring mainly adopts two methods:fixed-point with mobile re-measurement(Mobile Gravity)and fixed station with continuous observation(continuous gravity).The gravity monitoring history of China can be classified into three stages.Before 1998,gravity monitoring was mainly carried out along tectonic block boundaries,active faults or areas with strong historical earthquakes,usually with relative measurement and without absolute measurement.The dynamic variation characteristics of gravity before a series of earthquakes,such as Haicheng M7.2,Tangshan M7.8 and Lijiang M7.0,were summarized.But few earthquake cases were predicted successfully,except for Haicheng earthquake.After 1998,with the crustal movement network construction,the gravity field of the Chinese mainland has been monitored by the high-precision absolute gravity survey.The large-scale variation information before the Wenchuan M8.0 earthquake has been obtained.Effective opinions for the medium-term prediction of the Wenchuan earthquake are given.After 2010,taking the Crustal Movement Observation Network of China(CMONOC)as the base,several gravity networks such as the North China network and the North and South belt Gravity network were integrated and unified.Then a high-precision and complete gravity observation network over the China started to work.Several earthquakes with MS>6.0(such as Lushan M_S7.0,Men yuan MS6.4,Hutubi M_S6.2,etc.)were successfully predicted in that period.This is helpful for earthquake mechanism study and the medium-term earthquake prediction in China.With the improvement of measurement and long-term practice in gravity observation,a special interdisciplinary subject—"Seismic-gravimetry",is generated preliminarily.