关键词: 新疆, 热红外亮温, 相对功率谱, 异常特征分析

Abstract:

Xinjiang and its surrounding areas are one of the regions with the most frequent seismic activities and the largest intensity in the Chinese mainland. Therefore, conducting relevant earthquake prediction research is crucial for disaster prevention and mitigation. However, due to the limited natural conditions and other factors in the region, the number of site observation stations is small and the their distribution density is low. It is difficult to carry out earthquake prediction only using site observation. Remote sensing technology has the advantages of being all-weather and large-scale. With the development of remote sensing technology, many scholars have found that there are different degrees of thermal anomalies before strong earthquakes. At present, a variety of thermal anomaly extraction methods have been formed. Among them, the relative power spectrum method can remove the thermal radiation changes affected by non-tectonic activity factors such as topography, ground object types, and meteorology to highlight the thermal radiation anomalies caused during earthquake preparation. This method has been applied in Xinjiang and surrounding areas for many years. However, in the past few years, the technique for studying seismic thermal anomalies in Xinjiang and its surrounding areas has primarily focused on a single seismic event, lacking systematic combing of earthquake cases and analysis of prediction efficiency.

To further summarize the characteristics of seismic thermal infrared anomalies in Xinjiang and its surrounding areas, improve its prediction indicators, and improve the scientific and accuracy of earthquake prediction in this area, based on the blackbody brightness temperature data of FY-2 geostationary meteorological satellite, we extract the thermal infrared relative power spectrum anomaly of Xinjiang and surrounding regions from 2008 to 2021 by using the relative power spectrum method and analyze the prediction efficiency of earthquakes with different magnitudes, and summarizes the relationship between thermal infrared anomalies and corresponding earthquakes. The results show that: 1)The band 1 of the thermal infrared relative power spectrum has the highest corresponding rate of 44% for earthquakes above 5 in Xinjiang and its surrounding areas, but only 6.0-6.9 earthquakes have passed the significance test. The R-value is 0.342, which is greater than R₀(0.306). The dominant occurrence time of M5.0-5.9 earthquakes is within 3 months after the beginning of the anomaly and within 0.5 months after the end of the anomaly, while that of M6.0-6.9 earthquakes is three months and 7-12 months after the end of the anomaly. The dominant seismogenic areas of each magnitude range are within 200km from the edge of the anomaly area to the surrounding area. 2)The abnormal area and duration of the 6.0-6.9 earthquakes corresponding to the thermal infrared relative power spectrum anomaly positively correlate with the magnitude, and all pass the significance test. The peak and magnitude did not pass the significance test in the two magnitude ranges. 3)This anomaly occurs most frequently in the Altun area and has a high correspondence rate. The seismic correspondence ratio in the southern Xinjiang region is higher than that in the northern Xinjiang region; The anomaly in the basin has a higher seismic correspondence ratio and higher earthquake magnitude; 4)Most anomalies occurred in spring, and the seismic correspondence ratio of anomalies in autumn was the highest; 5)The proportion of epicenter mechanism solution types of corresponding earthquakes is consistent with that of various kinds in Xinjiang, and most events were shallow earthquakes. Shallow earthquakes may be more likely to cause thermal infrared anomalies.

Key words: Xinjiang, thermal-infrared brightness temperature, relative power spectrum, anomaly characteristics