于田7.3级地震前MODIS卫星热红外异常分析

ANALYSIS ON THERMAL INFRARED ANOMALOUS TEMPERATURE INCREASE OF MODIS SATELLITE BEFORE YUTIAN M_S7. 3 EARTHQUAKE

收集了2014年1—2月新疆于田7.3级地震区连续的MODIS/Terra卫星遥感热红外资料,经过去云等数据处理,选取观测质量最佳的北京时间凌晨4—6时的热红外数据进行地表温度反演,分析地震前后地表温度异常时间演化过程及其异常空间分布与活动断裂的关系,并讨论了震区地形地貌、季节性气候以及雨雪天气等非构造因子对地温异常的影响。结果表明：1）在于田地震发生前1个月震中附近出现热红外异常增温现象,异常增温与发震时间有一定的对应性。显著增温主要表现在震前半个月左右;在临震前5-6d,增温异常达到峰值,震后温度迅速下降;2）与地形地貌、季节性气候以及雨雪天气等非构造因子的相关分析表明,震前反映出反季节变化的构造＂增温＂信息,雨雪天气对震区异常升温产生一定程度的影响;3）震中附近西南部的谷地、盆地断裂构造复杂,热红外异常增温起始于此,并沿断层逐步向震中迁移;4）异常升温区域呈条带状,与宏观考察的NE向主破裂带一致;充分考虑地形地貌、季节性气候、雨雪天气等非构造因素对异常升温的影响,认为此次热红外升温可能为震前短临异常现象。

In this study, the continuous thermal infrared data of MODIS/Terra satellite remote sensing of the Yutian Ms7.3 earthquake area from January 2014 to February 2014 are collected, and by cloud- removing, the thermal infrared data between 4：00am-6：00am in Beijing time which is the best period for observation to conduct land surface temperature data retrieval, are selected. Time evolution process of land surface temperature anomalies before and after the earthquake is analyzed as well as the relationship between abnormal spatial distribution and active fault. Then, the impact of non-structural factors such as topography of earthquake area, seasonal climate, rain and snow on land surface temperature anomalies is discussed. The result shows that： a） There was phenomenon of thermal infrared abnormal temperature increase appearing near the epicenter area one month before the Yutian earthquake, and there was a certain correspondence between the abnormal temperature increase and earthquake occurrence time. The significant temperature increase happened in the first half of the month, while 5 to 6 days before the earthquake, the abnormal increase reached its peak, and the temperature dropped rapidly after the earthquake, b）Through the relative analysis of non-structural factors such as earthquake area＇s topography and landform, seasonal weather, rain and snow, the anti-seasonal structural ＂temperature increase＂ signals were discovered, and the rain and snow had a certain degree of influence on the abnormal temperature increase of the earthquake area. c） Due to the complex and sensitive fault structures of the valleys and basins at the southwest of the epicenter, the thermal infrared abnormal temperature increase usually starts from this area and gradually migrates to the epicenter along the faults, d）Abnormal temperature increase zone presents strip distribution which is in consistent with the NE-striking main fault zone. After full consideration of the influence of non- structural factors on the abnormal temperature increase, it was inferred that this thermal infrared temperature increase could be a short-imminent precursor before the earthquake.