利用锁眼卫星影像提取历史地震同震位移——以1976年土耳其Chaldiran地震为例

大地震的地表破裂及形变特征对研究地震成因机制、断层运动及大陆变形具有重要意义。随着卫星技术的日益成熟,自1992年美国加州Landers地震以来,光学和雷达影像被广泛应用于同震破裂、震后形变等定量研究。然而,由于缺乏更早之前的影像资料,90年代以前的历史地震研究无法深入。美国锁眼卫星KH-9影像的公开解决了震前卫星影像匮乏的问题,为研究70~90年代历史地震提供了可行的条件。首先借助伊朗Tabas-e-Golshan地震和Khuli-Boniabad地震的研究实例,概述了KH-9卫星影像测量历史同震位移的方法与进展;然后利用1976年(震前)和1980年(震后)的KH-9影像对1976年土耳其Chaldiran地震的同震位移进行了计算,测得该地震东西向同震位移量为(3.1±0.7)m,与实地测量的地表位移相符,表明该走滑地震没有明显的浅部滑动亏损现象;最后对KH-9卫星影像定量研究历史地震的未来应用和限制进行了讨论与总结。

Extracting Surface Displacements of Historical Earthquakes Using KH-9 Satellite Images:A Case Example of 1976 Chaldiran Earthquake,Turkey

Surface ruptures and deformation of large earthquakes are important for investigating earthquake mechanisms, fault activities and continental deformation. With the improvement of satellite techniques, optical and radar images have been widely used in earthquake studies since the 1992 Landers earthquake.However, due to a lack of pre-earthquake images, historical earthquakes prior to the 1990 s are rarely studied.Recent declassification of American KeyHole(KH) satellite images opened up new possibilities of investigating old earthquakes back to the 1970 s. Researchers have successfully applied KH-9 images to the 1978 Tabas-e-Golshan and 1979 Khuli-Boniabad earthquakes in Iran, and gained some new insights into fault behaviours. We first provided a review of the methodology and progresses of using KH-9 images to measure earthquake deformation, then investigated the 1976 Chaldiran, Turkey earthquake by matching the pre-and post-earthquake KH-9 images,and obtained an E-W displacement of about(3.1±0.7) m(i.e. strike-slip),consistent with the measurements in the field. KH-9 imagery provides a new means of investigating historical earthquakes in detail, but there are some limitations. These limitations are briefly discussed in the end.