Time-frequency Characteristics Of Seismic Temperature And Displacement Anomalies Based On Thermal Radiation Remote Sensing And GNSS

Earthquake is one of the main forms of energy release inside the earth.The tremendous energy generated by earthquakes could cause enormous loss of life and property.Therefore,earthquake prediction is of utmost importance to mitigate the impacts of earthquake disasters,yet it is a very challenging scientific problem.Interpretation of fault temperature and displacement change patterns is an effective means to recognize earthquake process and predict earthquakes.By analyzing the anomalies of fault temperature and displacement changes caused by earthquakes,we can identify and measure fault slip characteristics as well as monitor and study the motion status of seismic faults,thus improving earthquake prediction.The results of this dissertation can be extended and applied to improve earthquake prediction in terms of promoting disaster prevention timeliness and capability.This dissertation analyzed the characteristics of remote sensing temperature and GNSS displacement anomalies caused by earthquakes,proposed a time-frequency analysis method based on multi-scale wavelet transform and FFT power spectrum method with different window lengths,and processed the thermal radiation temperature surface structure data and GNSS displacement line structure data.The following main results were obtained.1.Through the analysis of the Wenchuan earthquake of magnitude 8.0 on May 12,2008 and the Nepal earthquake of magnitude 8.2 on April 25,2015,characteristics of earthquake temperature and displacement anomaly were obtained,,which consisted of parameters such as characteristic period,anomaly amplitude,and anomaly range and anomaly time.The feasibility and reliability of the time-frequency analysis method for processing remote sensing temperature and GNSS displacement data have been analyzed and verified.2.Comparative analysis of the commonness and heterogeneity of temperature and displacement anomalies yielded the spatio-temporal dynamic evolution of the frequency spectrum during temperature anomalies,the advantages of determining the earthquake time,and the disadvantages of judging the epicenter and magnitude.We also obtained the time evolution of the time-frequency spectrum during displacement anomalies as well as the advantages in epicenter and magnitude determination.3.Comprehensive analysis of the time-frequency characteristics of temperature and displacement anomalies achieved the segmentation characteristics of fault slip during the earthquake incubation process,namely the pre-trend slip phase of the fault,the instant phase of fault rupture(earthquake occurrence)and the slip phase of the fault rebound.Temperature and displacement changes during fault energy accumulation and release were also identified.This dissertation obtained the following innovative results.1)By applying time-frequency analysis to process GNSS displacement time series data,we obtained the spectral characteristics of fault sliding displacement anomalies.As the increased frequency information improves the accuracy of displacement anomaly identification,it is of great significance to improve the prediction of earthquake magnitude and occurrence time.2)By integrating thermal radiation remote sensing temperature and GNSS displacement observations,we established an internal relationship between temperature and displacement through fault slip,which is helpful for analyzing characteristics of the earthquake process as well as determining the occurrence time and location.