【作者】 陈顺云；

【导师】 马瑾； 刘力强； 刘培洵；

【作者基本信息】 中国地震局地质研究所 ， 固体地球物理学， 2006， 博士

【摘要】 卫星遥感影像在地球科学中的应用越来越广泛, 90年代初期便有学者开始尝试运用热红外遥感影像来预报地震。然而由于遥感本身的复杂性,加之地震预报属于世界性难题,运用热红外遥感影像进行地震预报的尝试,迄今为止仍未成为一种普遍接受的可靠的预报方法,这还需要长时间的探索。目前,一方面所报道的地震前出现的热红外辐射异常现象缺乏可靠检验,另一方面地震引起热红外辐射异常的物理机理也不太清楚。需要探索新的思路和方法。事实上,地震只是构造变形中的一种,多数构造变形并不引起地震。现今构造活动是把异常与地震联系起来的地质载体,起到桥梁作用,是问题的关键所在。将目标从利用热红外遥感研究地震预报转为研究现今构造活动,显出更加明确的物理基础,更有现实意义。利用遥感技术探测活动断层现今活动属于新思路,许多工作需从头开始。本文以热红外遥感资料为基础,采用定量化、物理化思路,从5个方面开展探索现今构造活动的定量热红外遥感方法研究。首先,引入定量遥感方法,对卫星影像进行大气校正,获取地表热红外辐射;其次,分析非构造因素对地表热辐射的影响,获取地表亮温年变稳定场和与构造活动密切相关的年变残差低频分量;再次,根据构造因素与非构造因素对地表热辐射影响的空间差异提出均值梯度法,突出构造活动信息;然后,介绍了透热指数法,以反演地下热信息;最后,进行地表热红外辐射与其它测量手段的综合对比分析。主要取得了4方面进展:(1)利用分离窗方法,获得了在地震研究中适用又能反映地表热红外辐射的地表亮度温度。地表亮度温度指与地表有相同辐射亮度的黑体之温度,简称地表亮温(LSBT)。地表亮度温度代表地表的热红外辐射能量(亮度),而非温度。地表热红外辐射传播至卫星时必然受到大气的干扰,这正是利用热红外遥感影像寻找构造活动信息,首先要遇到的难点。以地表亮温作为反演目标,既回避了地表比辐射率的影响,又能达到分离大气影响的目的。这对于地震研究更有现实意义。根据AVHRR热红外遥感资料,采用分离窗法反演获得了中国大陆20余年的地表亮度温度,为应用热红外遥感研究构造活动或地震提供了基础。结果显示大气在地表热红外辐射传播至卫星的过程中大约造成10K左右的影响。(2)利用小波分析方法,分析了各种非构造因素对地表热辐射的影响,获得了可作为背景的地表亮度温度年变基准场;进一步提取了与构造活动密切相关的年变残差低频分量TLOW。地表热红外辐射的影响因素较多,不仅受到构造活动的影响,还受到大气、太阳以及植被等多种非构造因素的干扰,并非所有地表红外异常都与构造活动或地震有关。排除非构造因素的影响,是利用热红外研究构造活动的另一难点。本文采用小波分析理论分析了太阳等非构造因素对地表热红外辐射的影响,将LSBT分解为3个具有不同物理背景的成份。然后获取了地表亮温的年变基准场。地表亮温可表示为年变基准场和年变残差之和:LSBT=Tsta+△T。其中,Tsta为LSBT的年变基准场; ?T为LSBT的年变残差。地表的能量主要来自太阳,找到了年变基准场,相当于找到的LSBT的最大干扰源,相应的构造活动信息包含于年变残差这中。最后,对年变残差?T的深入分析表明年变残差低频分量TLOW频段可能具有更高的信噪比,TLOW的热异常含有更多的由断层活动引起的热信息。TLOW的高温异常区(条带)跟构造特征、地震活动密切相关。(3)提出均值梯度法:改善数据精度,突出了构造活动信息。根据构造因素与非构造因素对地表热辐射影响的空间差异提出均值梯度法,突出构造活动信息。该方法的基本特点是,首先以损失一定时间信息为代价获取更高的数据精度,然后根据大气和构造活动对地表热辐射影响的不同,利用热辐射梯度突出正在活动的断裂带的空间展布。更多还原

【Abstract】 Remote sensing is widely utilized in geosciences. Thermal infrared images have been used to predict earthquakes since 1990. However, thermal infrared anomaly is not yet a reliable, stable and testable evidence for predicting earthquakes because earthquake prediction is a difficult issue in the world, as well as the complexity of remote sensing itself still exists. On one side, the infrared anomalies reported are not accepted generally owing to lack of reliable verification. On the other side, its mechanism is not clear. In fact, tectonic activities are results from crustal motion. And it is accepted generally that earthquakes are generated by fast motions along faults. Current tectonic activity is a geological tie between anomalies and earthquakes, and is a key to answer the problem. Therefore, shift of research focus from seeking seismic precursors to monitoring processes of fault activity can provide definite physical evidence for the earthquake prediction and is more significant.It is a new approach to use remote sensing technology to detect the current tectonic activity, which faces many new difficulties. In this thesis, studies of five aspects on current tectonic activity are made by quantitative and physical methods, based on thermal infrared remote sensing data. First, land surface thermal infrared radiation is extracted by the quantitative remote sensing method. Second, influence of non-tectonic factors is analyzed with the wavelet method. Third, space effect on the current tectonic activity is extruded from the thermal radiation field of land surface by the difference between influence of atmosphere and tectonic activity on land surface. Fourth, the Heat Penetrability Index (HPI) method is applied to get the underground thermal information. At last, information on tectonic activity extracted from thermal infrared radiation is compared with that of other methods.The new contributions of this thesis are summarized as follows:(1)Land surface brightness temperature (LSBT), which is an important parameter for studying earthquakes and presents thermal infrared radiation(TIR) of land surface, is extracted by the split-window method. LSBT is the temperature of black body with the same irradiance of land surface. Although LSBT and temperature have the same dimension, LSBT is representative of thermal radiation energy, but not temperature. The remote sensing data are reformed by interference of the atmosphere. The first task for extracting information of tectonic activity is to remove interference for acquisition of useful information is. LSBT is chosen as an inverse target. Not only emissivity of land surface is avoided, but also atmosphere correction is realized. This is more practically significant for studying earthqaukes. LSBT in the mainland of China is obtained from NOAA/AVHRR data from 1981 to 2001 by split-window method. The result shows that atmosphere influence on LSBT from land surface to satellite-based sensor is about±10K.(2)Using the wavelet method, influence of non-tectonic factors is analyzed, and annual variation field and the low frequency band of LSBT are extracted. Thermal infrared radiation of land surface bears on many factors such as tectonic activity, atmosphere, solar radiation, plant and so on. Not all thermal infrared anomalies are attributed to earthquakes. How to exclude the non-tectonic information is the second problem for studying tectonic activities or earthquakes with TIR. The influence factors of thermal radiation of land surface are studied by the wavelet analyses based on frequency difference between tectonic and non-tectonic factors. Stable annual variation更多还原