| Earthquakes are one of the most devastating natural disasters,causing enormous damage to the development of human society.The prediction of the time,location and intensity of earthquakes is therefore one of the most effective means of preventing seismic hazards.The accumulation of tectonic stresses in the earthquake incubation zone prior to an earthquake can cause abnormal changes in a variety of geophysical and chemically relevant parameters in the subsurface,surface and atmosphere.The anomalous correlation and coupling of seismic parameters before and after earthquakes is of great scientific importance and practical significance for earthquake prevention and disaster reduction,as well as for understanding the possible physical mechanisms of anomalous changes in relevant parameters and predicting the urgency of future earthquakes.This study focuses on the correlation and coupling effects of seismically relevant parameters.Firstly,a qualitative and quantitative comparison of two commonly used seismic anomaly extraction methods,the Z-score(ZS)method and the Robust Satellite Technology(RST)method,was carried out in terms of the anomaly extraction effectiveness of actual cases and the ability to set anomalies for identification.Afterwards,a combined spatial-ground multi-parameter anomaly characterization of the 2017 Jinghe Mw6.3 earthquake was carried out using the ZS method and combined with other literature to analyze the multi-parameter spatial-temporal coupling correlation of the Jinghe earthquake and explore the possible physical mechanisms.Then,an improved ZS method based on spatial-temporal weighting is proposed and applied to the extraction of spatial-temporal features of anomalous changes in surface and air temperatures before the Yangbi Ms6.4 and Mado Ms7.4 earthquakes in 2021,based on the spatial-temporal characteristics of multi-parameter anomalies before the earthquakes,and the deep gestation environments and possible physical mechanisms of these two earthquakes are discussed.Finally,a statistical analysis of Pearson correlations between multiple parameters between the seismic and non-seismic years of earthquakes of magnitude 6 or higher occurring in western mainland China since2008 was carried out to obtain quantitative relationships between the spatial and temporal characteristics of different parameters and to explore the similarities and differences in the correlations between the parameters in different regions.The main results and conclusions achieved in the thesis are as follows:(1)Using the 2014 Yutian Mw6.9 earthquake as a typical earthquake example,the effectiveness and reliability of the commonly used seismic anomaly extraction methods:the ZS method and the RST method were evaluated qualitatively and quantitatively in five aspects: the extraction effect of actual earthquake cases,the sensitivity of anomaly changes,the accuracy of different types of set anomaly extraction,the ability to suppress background information,and the indication of future earthquake epicenters.The deeper reasons for the discrepancies were analyzed.The results show that the ZS method is a reasonable and simple way to extract seismic anomalies.(2)Using the ZS method,a study on the spatial-temporal distribution characteristics of the joint star-ground multiparameter anomaly of the 2017 Jinghe Mw6.3 earthquake was carried out,and combined with the results of other parameters in the published literature,a comprehensive analysis of the coupled spatial-temporal association of the multiparameter anomaly before and after the Jinghe earthquake was carried out,and the possible physical mechanisms were explored.The Jinghe pre-earthquake multiparameter anomaly has a chain effect in time and the spatial distribution overlaps with the stress accumulation zone,and the p-hole model is a more appropriate physical mechanism for the multiparameter anomaly.(3)The improved ZS method was successfully applied to the study of the spatial and temporal distribution characteristics of surface temperature and air temperature anomalies before the 2021 Yangbi Ms6.4 and Mado Ms7.4 earthquakes,based on the characteristics of pre-earthquake multiparameter anomalies,and was improved through spatial and temporal weighting to explore the differences in the anomalous changes of temperature parameters between the two earthquakes and the possible physical mechanisms.The temperature parameter anomalies are distributed around the fracture zone and the improved ZS method outperforms the original ZS method in both the actual seismic example and the set anomaly extraction.(4)The Pearson correlation coefficients between surface temperature,air temperature,latent heat flux and clear-sky outgoing longwave radiation in earthquake years and non-earthquake years were calculated for each earthquake case,taking the earthquakes of magnitude 6 or above that occurred in western China since 2008 as typical examples,to obtain quantitative relationships of spatial and temporal correlations between different parameters,and to explore the similarities and differences of parameter correlations in different regions.The seismogenic process changes the correlation between the parameters,and the areas of significant correlation change are located around the epicenter and the fault zone. |
