基于多轨道卫星观测数据分析尼泊尔地震长波辐射特征

Analyzing long wave radiation data associated with the 2015 Nepal earthquakes based on Multi-orbit satellite observations

综合已经在红外异常提取中应用的涡度和RST(Robust Satellite Technique)算法优点,提出了红外异常指数算法.并基于长时间尺度的中国静止卫星FY-2D和美国极轨卫星NOAA长波辐射数据,应用RST和异常指数算法,分别对2015年4月25日尼泊尔M_s8.1和5月12日M_s7.5地震前后卫星长波辐射变化特征进行了分析,开展了多轨道、多时空分辨率长波辐射同步地震热红外特征研究.结果表明,运用RST算法,两次地震前后,未能在震中周围发现明显的长波辐射异常.运用异常指数算法:(1)对于NOAA卫星,4月15日在M_s8.1地震震中以西出现热红外异常,到4月24日震中以西约100 km处出现异常最大值,随后逐渐消失.5月10日在M_s7.5地震震中以东约200 km发现异常;(2)在NOAA卫星长波辐射异常发现最大值当日,采用FY-2D卫星每3 h的数据分析可发现红外异常的动态演化过程,弥补NOAA卫星分辨率不足.以上结果为利用多轨道卫星监测地震热辐射变化提供了依据.

The infrared anomaly index algorithm is proposed in this paper based on the advantages of RST （Satellite Technique Robust） and vorticity algorithm which have been used in application of detecting infrared anomaly. An MS8.1 and an MS7.5 earthquake, occurred at the front of the India-Eurasia collision belt, struck Nepal on April 25th and May 12th, 2015. We analyzed the temporal and spatial variations of outgoing long wave radiation （OLR） obtained from satellite observations around the time of the two earthquakes using RST and anomaly index algorithms. The Meteorological satellite data we used include night-time data （once daily） from the polar orbit NOAA/AVHRR and three hours data （8 times daily） of the Chinese geostationary satellite FY-2D.#br#The results show that RST algorithm provides no anomalous solutions around the epicenter of two earthquakes. In comparison the infrared anomaly index algorithm did provide an anomaly detection, and specifically we found an increase of emitted infrared radiation on the west of the MS8.1 epicenter on April 15th 2015. The thermal anomaly derived from NOAA data reached the maximum on April 24 at 100 kilometers west of the MS8.1 epicenter, and then disappeared gradually. In addition another thermal anomaly was detected on May 10 at 200 kilometers east of the MS7.5 epicenter. Based on three-hour data analysis from FY-2D, we found on April 24 a dynamic evolution in the anomalous process, the same day when the NOAA data thermal anomaly reaches the maximum. In this case FY-2D satellite data provided complimentary data to the initial detection based on low temporal/spatial resolution data obtained from NOAA and improved the final solution in the location of the anomaly. Our initial results suggest that systematic use of multi-orbit satellite observation can provide reference to monitor the pre-earthquake changes of thermal radiation.