The research on the relationship between satellite infrared remote sensing and earthquakes dates back to the 1980s(Gorny V.I. et al., 1988). With the development of satellite remote sensing technology, many countries in the world have conducted research on earthquake thermal radiation(Gorny V.I. et al., 1988; Tronin A.A., 1996, 1999, 2000; Tronin A.A. et al., 2002; Saraf A.K. et al., 2005a, 2005b), including China (Qiang Zuji et al., 1991a, 1991b; Xu Xiudeng et al., 1995; Ma Jin et al., 2006; Zhang Yuansheng et al., 2004, 2010). Qiang et al. (1991) have found that anomaly areas were consistent with seismic zones or active tectonics, and the epicenter is mostly located in the intersections of stress tropicals (Qiang Zuji et al., 1991a, 1991b, 1991c, 1992, 1997, 1998, 1999). Xu et al. (1995) have found that there were clearly distinguishable and busty characteristics of infrared impending abnormal(Xu Xiudeng et al., 1995). Ma et al. (2006) have found that the Mani earthquake infrared anomaly was closely related to the activities of the Altyn Tagh fault, which illustrated the interaction of faults and defection among the deformation exception, current fault activities and earthquakes (Ma Jin et al., 2006). According to numerous infrared remote studies, there were thermal anomalies before great earthquakes. It was a natural phenomenon that happened during the earthquake process. For seismic thermal infrared research, extracting anomalies was important and difficult because of the weak signal and complicated background noise factors.
Since 2000, Zhang and his teammates have carried out seismic thermal infrared research on abnormal extracting, case studying and mechanism investigating (Zhang Yuansheng et al., 2002, 2004, 2010, 2011; Guo Xiao et al., 2010; Wei Congxin et al., 2011; Wei Congxin, 2011; Zhang Xuan et al., 2013), have proposed the "Time-Frequency Relative Power Spectrum" (T-F RPS) method based on the China Geostationary Meteorological Satellite (FY-2C/FY-2E) infrared remote sensing brightness temperature data processing, and have formed the "Union Origin Mechanism" for the explanation of pre-earthquake thermal anomalies(Zhang Yuansheng et al., 2010). In recent years, we tried to do a few earthquake prediction tests by using Satellite infrared remote sensing data before the earthquake, to find out the anomalies before earthquakes. We need to understand the evolution characteristics of anomalies in time and space. We tracked Thermal Infrared Anomalies for the April 16, 2013 MW7.8 of Khash, Iran Earthquake and found the unique characteristics of process and distribution.1 DATA PROCESSING
The object thermal infrared information (which is TBB) was affected by the basic field including basic earth temperature, annual variation temperature, topography and geomorphology, and was also influenced by the change field, including daily variation temperature, short time no-seismic temperature changes and earthquake factors. So, seismic thermal infrared anomaly was weak and complicated to extracting. By the method of second and seventh order Wavelet Transform (WT), we firstly suppressed the basic earth temperature field (direct circulating part), annual variation temperature field, daily variation temperature field, temperature changes caused by the rain clouds, cold-heat air currents, and other factors (including earthquakes). Then, we obtained the dominant frequency and the peak-to-peak amplitude value by using the Relative Power Spectral (RPS) method. After using the Wavelet Transform and Relative Power Spectrum (RPS) method, we obtained the time-frequency space data with the dominant frequency and amplitude and effectively removed the non-seismic anomaly factors and also highlighted seismic thermal radiation anomalies. This method was called "Time-Frequency Relative Power Spectrum" (T-F RPS).
There are two aspects for data processing. Firstly, Geostationary Meteorological Satellite data is more suitable than Polar Orbit Satellite on earthquake research because of consistency contrast and place comparability. The satellite data used in this paper is taken from the China Geostationary Meteorological Satellite (FY-2C/FY-2E) infrared remote sensing brightness temperature data, which was received from the station of the Geostationary Meteorological Satellite at the Lanzhou National Geophysical Research Observatory Station of the Lanzhou Institute of Seismology, China Earthquake Administration and Satellite Meteorological Center of China Meteorological Administration. The time range of the effective data was from January 1, 2007 to April 16, 2013 and five midnight observation data were selected every day because there was little solar radiation in the night. Secondly, we used T-F RPS method for treatment of the Geostationary Meteorological Satellite brightness temperature data. There are four steps for data calculating: (1) Cloud, cold and warm current cause short-cycle changes. the partial cloud influence was removed by The second order of the wavelet with making up the window law, and then we calculated the mean value of these data to obtain the labor-day wage (Zhang Yuansheng et al., 2010). (2) We gained a waveform of brightness temperature data (2nd-order criterion function and 7th-order criterion function cancellation) with positive and negative phases in time domain for each pixel. (3) Using the Relative Power Spectral (RPS) method, we can obtain the dominant frequency and the peak-to-peak amplitude value. The time window length (n=64 days) and sliding window length (n=1 day) were used to calculate the power spectrum with Fast Fourier Transformation (Zhang Yuansheng et al., 2010). (4) The method of information extracting of earthquake thermal infrared anomalies used in this paper was time-frequency map. We effectively removed the non-seismic factors and highlighted earthquake thermal infrared anomalies by scanning the time-frequency space data in the whole space-time and full band.2 RESULTS
The April 16, 2013 MW7.8 earthquake east of Khash, Iran, occurred as a result of normal faulting at an intermediate depth in the Arabian plate lithosphere, approximately 80km beneath the Earth's surface. Regional tectonics is dominated by the collisions of the Arabian and India plates with Eurasia at the longitude of this event. Arabian plate lithosphere is sub-ducted beneath the Eurasian plate at the Makran coast of Pakistan and Iran, and becomes progressively deeper to the north(Fig. 1(a)).
Pre-earthquake thermal infrared anomalies presented X-Type model distribution of north-east and near north-south strip, are mainly distributed in the east of Iran Khash, Iran. The epicenter was located near the intersection region the X-Type abnormal migration process (Fig. 1(b)).2.1 Spatial Evolution of Pre-earthquake Thermal Infrared Anomalies
Spatial evolution of pre-earthquake thermal infrared anomalies mainly showed the process of appears, maximum and disappear. In early March, thermal infrared anomalies appeared around the epicenter region (region B) and north of the epicenter (region A). Then, two abnormal areas continued to extend (region C) and abnormal amplitude increases gradually. Abnormal areas near the epicenter diffused to the northeast and formed the NE stripe distribution. The connections between near and the north epicenter was approximately a NS strip distribution. The two bands composed the X-Type model of NE and NS stripe. The abnormal range and abnormal amplitude reached maximum at the end of March in 2013. In early April in 2013, the abnormal areas were gradually reduced and continued to the occurrence time (Fig. 2).
The durations of pre-earthquake thermal infrared anomalies were up more than 40 days or and the maximum amplitude was about 18 times. The earthquake occurred 20 days after the abnormal maximum amplitude which appeared on March 26, 2013. In the past six years, there was only a long duration (more than 40 days) and greatly amplitude (greater than 8) thermal infrared anomalies in the region (Fig. 3).
After using the T-F RPS method based on the China Geostationary Meteorological Satellite (FY-2C/ FY-2E) infrared remote sensing brightness temperature data processing, we extracted and identified seismic thermal radiation anomalies for the April 16, 2013 MW7.8 of Khash, Iran Earthquake. The thermal infrared anomalous characteristics, including characteristic period, characteristic amplitude, abnormal duration and abnormal morphology, were obvious and valuable on pre-earthquake thermal infrared research. The epicenter was located at the edge of local positive thermal anomaly and near the intersection region of the X-Type abnormal migration process, which was consistent with the rock test results (Wang Qingliang et al., 1998; Wu Lixin et al., 2004a, 2004b, 2004c, 2004d). The direction of abnormal distribution is basically the same as that of the seismogenic fault. The overall evolution of the thermal anomaly showed as the appear-strengthen-shrink-disappear process. The amplitude of relative power spectrum increases suddenly and drops sharply. The seismic activity in this research area is frequent. A large number of seismic case analyses in the future can improve the accuracy of earthquake prediction.
After studying a large number of strong earthquake cases, we found that there were obvious and valuable pre-earthquake thermal infrared anomalies of earthquakes above MS7.0. We also found that pre-earthquake thermal infrared anomalies of earthquakes from MS6.0 to MS 6.9 were very different between mainland and adjacent sea earthquakes (Wei Congxin, 2011). Thermal infrared anomalies of mainland MS6.0 earthquakes were clearly extracted and identified. In this paper, we also should be sure that, the satellite thermal infrared remote sensing information can be used as the impending earthquake exception for earthquake prediction and forecasting test. Abnormal distribution of the X-Type model related to the geological structure of the region (Hessami K. et al., 2006).
|Gorny V.I., Salman A.G., Tronin A.A., Shilin B.B. The earth outgoing IR radiation as an indicator of seismic activity[J]. Proceedings of the Academy of Sciences of the USSR, 1988, 30(1): 67–69 .|
|Guo Xiao, Zhang Yuansheng, Zhong Meijiao, Shen Wenrong, Wei Congxin. Variation characteristics of OLR for the Wenchuan earthquake[J]. Chinese Journal of Geophysics, 2010, 53(11): 2688–2695 (in Chinese with English abstract).|
|Hessami K., Jamali F. Explanatory notes to the map of major active faults of Iran[J]. JSEE: Spring, 2006, 8(1): 1–11 .|
|Lu Zhenquan, Wu Bihao, Qiang Zuji, Du Letian. Brightness temperature anomalies in satellite-based thermal infrared remote sensing along the offshore China Seas[J]. Geoscience, 2005, 19(1): 74–82 (in Chinese with English abstract).|
|Ma Jin, Chen Shunyun, Liu Peixun, Wang Yipeng, Liu Liqiang. Temporal-spatial variations of associated faulting inferred from satellite infrared information: a case study of the N-S seismo-tectonic zone in China[J]. Chinese Journal of Geophysics, 2006, 49(3): 816–823 (in Chinese with English abstract).|
|Qiang Zuji, Xu Xiudeng, Dian Changgong. Impending-earthquake satellite thermal infrared and ground temperature increase anomalies[J]. Chinese Science Bulletin, 1991, 36(22): 1894–1900 .|
|Qiang Zuji, Xu Xiudeng, Dian Changgong. Thermal infrared anomaly precursor of impending earthquakes[J]. Chinese Science Bulletin, 1991, 36(4): 319–323 .|
|Qiang Zuji, Xu Xiudeng, Dian Changgong. Thermal infrared anomalies under the non-temperature-increment background and the mechanism discussion[J]. Chinese Science Bulletin, 1991, 36(22): 1901–1906 .|
|Qiang Zuji, Dian Changgong, Wang Xuanji, Hu Siyi. Satellite thermal infrared anomalous temperature increase and impending earthquake precursor[J]. Chinese Science Bulletin, 1992, 37(19): 1642–1646 .|
|Qiang Zuji, Kong Lingchang, Zheng Lanzhe, Guo Manhong, Wang Geping, Zhao Yong. An experimental study on temperature increasing mechanism of satellitic thermo-infrared[J]. Acta Seismologica Sinica, 1997, 10(2): 247–252 . DOI:10.1007/s11589-997-0093-0.|
|Qiang Zuji, Dian Changgong. Satellite infrared brightness temperature anomaly-earthquake imminent precursor[J]. Science in China (Series D: Earth Sciences), 1998, 28(6): 564–573 (in Chinese).|
|Qiang Zuji, Dian Changgong, Li Lingzhi, Xu Min, Ge Fengsha, Liu Tao, Zhao Yong, Guo Manhong. Satellite thermal infrared brightness temperature anomaly image-short-term and impending earthquake precursors[J]. Science in China (Series D: Earth Sciences), 1999, 42(3): 313–324 . DOI:10.1007/BF02878968.|
|Saraf A.K., Choudhury S. Cover: satellite detects surface thermal anomalies associated with the Algerian earthquakes of May 2003[J]. International Journal of Remote Sensing, 2005a, 26(13): 2705–2713 . DOI:10.1080/01431160310001642359.|
|Saraf A.K., Choudhury S. Cover: NOAA-AVHRR detects thermal anomaly associated with the 26 January 2001 Bhuj earthquake, Gujarat, India[J]. International Journal of Remote Sensing, 2005b, 26(6): 1065–1073 . DOI:10.1080/01431160310001642368.|
|Tronin A.A. Satellite thermal survey—a new tool for the study of seismoactive regions[J]. International Journal of Remote Sensing, 1996, 17(8): 1439–1455 . DOI:10.1080/01431169608948716.|
|Tronin A.A. Satellite thermal survey application for earthquake prediction. In: Hayakawa M. (Editor), Atmospheric and Ionospheric Electromagnetic Phenomena Associated with Earthquakes[M]. Tokyo: Terrapub, 1999. 717-746.|
|Tronin A.A. Thermal IR satellite sensor data application for earthquake research in China[J]. International Journal of Remote Sensing, 2000, 21(16): 3169–3177 . DOI:10.1080/01431160050145054.|
|Tronin A.A., Hayakawa M., Molchanov O.A. Thermal IR satellite data application for earthquake research in Japan and China[J]. Journal of Geodynamics, 2002, 33(4/5): 519–534 .|
|Wang Qingliang, Wang Wenping, Liang Weifeng, Chen Bing. Stress-dissipative heat geotemperature precursor mechanism of earthquakes[J]. Acta Seismologica Sinica, 1998, 11(5): 615–621 . DOI:10.1007/s11589-998-0077-8.|
|Wei Congxin. Research on Seismic Thermal Radiation [D]. Master's thesis. Lanzhou: Lanzhou Institute of Seismology, China Earthquake Administration, 2011 (in Chinese with English abstract).|
|Wei Congxin, Zhang Yuansheng, Hui Shaoxing. Thermal-infrared of MS7.5 Andaman Islands earthquake on August 11, 2009[J]. Journal of Seismological Research, 2011, 34(2): 153–157 (in Chinese with English abstract).|
|Wu Lixin, Liu Shanjun, Wu Yuhua, Li Yongqiang. Remote sensing-rock mechanics (Ⅰ) —laws of thermal infrared radiation from fracturing of discontinous jointed faults and its meanings for tectonic earthquake omens[J]. Chinese Journal of Rock Mechanics and Engineering, 2004a, 23(1): 24–30 (in Chinese with English abstract).|
|Wu Lixin, Liu Shanjun, Wu Yuhua, Li Yongqiang. Remote sensing-rock mechanics (Ⅱ) —laws of thermal infrared radiation from viscosity-sliding of bi-sheared faults and its meanings for tectonic earthquake omens[J]. Chinese Journal of Rock Mechanics and Engineering, 2004b, 23(2): 192–198 (in Chinese with English abstract).|
|Wu Lixin, Liu Shanjun, Xu Xianghong, Wu Yuhua, Li Yongqiang. Remote sensing-rock mechanics (Ⅲ) —laws of thermal infrared radiation and acoustic emission from friction sliding intersected faults and its meanings for tectonic earthquake omens[J]. Chinese Journal of Rock Mechanics and Engineering, 2004c, 23(3): 401–407 (in Chinese with English abstract).|
|Wu Lixin, Liu Shanjun, Wu Yuhua, Li Yongqiang. Remote-sensing-rock mechanics (Ⅳ) —laws of thermal infrared radiation from compressively-sheared fracturing of rock and its meanings for earthquake omens[J]. Chinese Journal of Rock Mechanics and Engineering, 2004d, 23(4): 539–544 (in Chinese with English abstract).|
|Xu Xiudeng, Xu Xiangmin, Ma Shengdeng, Luo Yuan. Preliminary inquiry into the causes of anomaly increase of air temperature by an impending earthquake[J]. Acta Seismologica Sinica, 1995, 8(1): 149–154 . DOI:10.1007/BF02651008.|
|Zhang Xuan, Zhang Yuansheng, Wei Congxin, Tian Xiufeng, Feng Hongwu. Thermal infrared anomaly prior to Yiliang of Yunnan MS5.7 earthquake[J]. China Earthquake Engineering Journal, 2013, 35(1): 171–176 (in Chinese with English abstract).|
|Zhang Yuansheng, Shen Wenrong, Xu Hui. Satellite thermal infrared anomaly before the Xinjiang-Qinghai border MS8.1 earthquake[J]. Northwestern Seismological Journal, 2002, 24(1): 1–4 (in Chinese with English abstract).|
|Zhang Yuansheng, Guo Xiao, Zhang Xiaomei, Li Mingyong. Study on the inversion method of land surface temperature by applying IR bright temperature data of still satellite[J]. Northwestern Seismological Journal, 2004, 26(2): 113–117 (in Chinese with English abstract).|
|Zhang Yuansheng, Guo Xiao, Zhong Meijiao, Shen Wenrong, Li Wen, He Bin. Wenchuan earthquake: brightness temperature changes from satellite infrared information[J]. Chinese Science Bulletin, 2010, 55(18): 1917–1924 . DOI:10.1007/s11434-010-3016-8.|
|Zhang Yuansheng, Guo Xiao, Wei Congxin, Shen Wenrong, Hui Shaoxing. The characteristics of seismic thermal radiation of Japan MS9.0 and Myanmar MS7.2 earthquake[J]. Chinese Journal of Geophysics, 2011, 54(10): 2575–2580 (in Chinese with English abstract).|