关键词: 发震断裂, 卫星红外异常, 亮温均值, 亮温差值

Abstract: The Kunlun M_S8.1 earthquake took place on Nov. 14, 2001 in eastern Kunlun Mountains, Northwest China. Two methods are developed to extract the information of the satellite infrared anomalies prior to the earthquake. One is pixel-by-pixel analysis by subtracting the average brightness temperature 1 month before the event from the average brightness temperature in the same period in 2 000 pixel by pixel. The obtained image can be divided into two different regions: temperature increase and non-increase regions. The image shows that most regions in north Tibetan Plateau are temperature non-increase, but some temperature increase belts occur along active faults, and especially along the eastern Kunlun Fault. This temperature increase is considered to be earthquake precursor. The second method is based on the analysis of temperature difference inside and outside the fault zone. The inside region is defined as the buffer region created by GIS within 15km radius to the Hoh Sai Hu segment of the Eastern Kunlun Fault. The outside region is the buffer region in 15～30km radius to the inside region. This method is used to calculate the difference of the average brightness temperature for inside region and outside region in each night(0～8am) in 2001. The result shows that the temperature of the inside region is normally about 2℃ lower than that of the outside region. However, one and half months before the earthquake (beginning from Oct.2001),the brightness temperature of the inside region became 1℃ higher than that of the outside region. It returned to normal value after the event. The results indicate that the satellite infrared anomalies correspond spatially to the seismogenic fault. The temperature increase in the seismogenic fault belt is higher than that in the other regions. The analysis of temperature difference inside and outside the fault zone is an effective method for extracting the precursor information from satellite infrared images.

Key words: seismogenic fault, satellite infrared anomaly, average brightness temperature, difference of brightness temperature