Short Term and Imminent Earthquake Prediction Indicators for Fixed-Point Deformation Observation at Yunlong Station

ZI Chengzhu; HONG Min; YANG Shufeng; ZHANG Yuan; HEI Hetang; ZHANG Junyin

doi:10.13512/j.hndz.2025.04.07

Abstract：Based on historical earthquake examples,by analyzing the fixed-point deformation observation data of Yunlong Station from 2013 to 2023,the threshold of precursor anomalies and the characteristic images of imminent anomalies were obtained,providing a reference example for identifying precursor anomaly information of Yunlong Station's fixed-point deformation.The research results indicate that the short-term anomalies of water pipe tilt observation are mainly manifested as solid tide distortion and accelerated inclination,with a seismic interval≤60 days.It has good short-term indication for medium-strong earthquakes with M≥5 within a range of≤200 km around the measuring point.The strain observation of the cave body adopts the rate difference method with a threshold of 1.5 times the standard deviation,and the window anomaly method and the annual variation detection method take a threshold of 1 time the standard deviation.Earthquakes occur during the abnormal process or within 90 days after the end of the anomaly,with a prediction accuracy of 75%,all of which are evaluated by the R-value prediction efficiency.The three prediction indicators have important reference significance for the prediction of moderate-earthquakes within 300 km around the measuring point and can be applied to earthquake prediction practice as quantitative prediction indicators for tracking.Especially,the window anomaly method shows the advantages of high prediction accuracy,low false alarm rate and low omission rate.This indicator can be mainly used for strong earthquake prediction in western Yunnan.