基于Molchan检验的时变重力场地震预报效能评价

Evaluation of earthquake prediction efficiency in time-variable gravity field based on molchan test

地震前的区域重力场变化信号是判断年度地震危险性的依据之一.本文基于陆地时变重力观测获得的中国大陆西部重力场变化结果,采用Molchan检验方法对2018—2021年间中国大陆西部的12次5级以上地震前的重力场变化预报效能进行评价.研究结果表明:现有陆地时变重力测量得到的3年尺度重力变化结果,对于未来1年的5级以上地震风险具有独立的预报效能,明显高于泊松概率;时变重力水平总梯度作为定量表征重力场空间变化特征的指标,Moclchan检验结果显示其预报效能优于时变重力信号;发生在南北地震带的2019年张掖5.0级地震,夏河5.7级地震和2020年巧家5.0级地震Molchan检验的效果更好,这可能与南北地震带地区重力测网覆盖程度更好有关.本文研究结果客观和定量地评估时变重力场的预报能力具有重要意义,也可以为优化地震预测指标体系的建立提供一定的参考.

The variation signal of regional gravity field before an earthquake is one of the bases to judge the annual earthquake risk.In this paper,based on the results of the gravity field variation in the western Part of the Chinese mainland obtained from time-variable land gravity observations,the Molchan test method was used to evaluate the prediction efficiency of the gravity field variation before 12 earthquakes with magnitude above M 5 occurred in the western part of the Chinese mainland during 2018—2021.The results show that:the results of 3-year scale gravity changes obtained from existing land time-variable gravimetry have independent prediction efficiency for the earthquake risk above M 5 in the next year,which is obviously higher than poisson’s probability;the time-variable gravity horizontal total gradient is used as an index to quantitatively characterize the spatial variation characteristics of the gravity field.The results of Moclchan test show that its prediction performance is better than that of time-variable gravity signals;the 2019 Zhangye M 5.0,the Xiahe M 5.7 and the 2020 Qiaojia M 5.0 earthquake that occurred in the north-south seismic zone performed better in the Molchan test,which may be related to the better coverage of the gravity survey network in the north-south seismic zone.The research results of this paper are of great significance to objectively and quantitatively evaluate the prediction ability of the time-variable gravity field,and can also provide a certain reference for optimizing the establishment of the earthquake prediction index system.