Volcano-wide fringes in ERS synthetic aperture radar interferograms of Etna (1992-1998): Deformation or tropospheric effect?
Volcano-wide fringes in ERS synthetic aperture radar interferograms of Etna (1992-1998): Deformation or tropospheric effect?
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DOI：
10.1029/2000jb900095
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发表时间：
2000-07-10
影响因子：
3.9
通讯作者：
Froger, JL
中科院分区：
文献类型：
--
作者：
Beauducel, F;Briole, P;Froger, JL
埃特纳火山（海拔3300米）是最早也是利用差分合成孔径雷达研究最多的火山。之前的论文提供了整个建筑物大规模变形的证据，这与动乱事件相符，但与经典弹性模型不太吻合。此外，众所周知，大气对山区的影响非常显着。因此，干涉图可以反映变形和对流层效应两者。我们在这里研究直接从干涉图评估和校正对流层效应的可能性。从 1992 年到 1999 年拍摄的 38 个 ERS 合成孔径雷达上升场景中，我们计算了 238 个干涉图。数据量使我们能够分析如何在长时间内保持相干性，从而揭示永久散射的位置。通过对相位-仰角关系的简单分析，我们证明了分层对流层效应与具有地形的三维弹性体中的源产生的大规模变形之间的模式存在明显差异。通过结合反演过程，我们分析了完整的 238 个干涉图集的形变源和对流层效应。最后，为每个 SAR 图像检索参数的时间演化和建模概率估计。对流层延迟的估计相对变化随时间变化从 -2.7 到 +3.0 (+/- 1.2) 边缘。它们与基于同一时间段地面气象和全球定位系统观测的埃特纳火山的其他对流层估计一致。岩浆体积变化仍然低于误差线，因此无法正确估计。最后，一些干涉图可以完全用两个采集周期之间对流层条件的差异来解释，而不需要援引火山的变形。
Mount Etna (3300 m) is the volcano that has been first and most studied by differential synthetic aperture radar. Previous papers gave evidence for a large-scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models. Also, atmospheric effects on mountainous areas are known to be very significant. Accordingly, interferograms may reflect both deformation and tropospheric effects. We investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms. From 38 ERS synthetic aperture radar ascending scenes taken from 1992 to 1999, we have computed 238 interferograms. The amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters. From a simple analysis of phase-elevation relation, we give evidence for the clear difference in pattern between stratified tropospheric effects and large-scale deformation produced by a source in a Three-dimensional elastic body with topography. Using combination of inversion processes, we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms. Finally time evolution of the parameters and modeling probability estimation are retrieved for each SAR image. Estimated relative change in tropospheric delay varies in time from -2.7 to +3.0 (+/- 1.2) fringes. They are consistent with other tropospheric estimations at Etna based on ground met and Global Positioning System observations on the same period of time. Magmatic volume variations remain below error bars and thus cannot be estimated properly. Finally, some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods, without the need to invoking a deformation of the volcano.