Synthetic aperture radar interferometry of Okmok volcano, Alaska: radar observations
Synthetic aperture radar interferometry of Okmok volcano, Alaska: radar observations
复制标题
DOI：
10.1029/2000jb900034
复制
发表时间：
2000-05
影响因子：
--
通讯作者：
Zhong Lu;Dörte Mann;J. Freymueller;D. Meyer
中科院分区：
文献类型：
--
作者：
Zhong Lu;Dörte Mann;J. Freymueller;D. Meyer
利用ERS-1/ERS-2合成孔径雷达干涉仪研究了1997年阿拉斯加奥克莫克火山喷发。首先，我们利用串联的ERS-1/ERS-2影像对和已有的DEM建立了精确的数字高程模型(DEM)。其次，通过研究干涉相干性的变化，我们发现新喷发的熔岩在喷发后5-17个月内失去了雷达相干性。这表明表面后向散射特性发生了变化，可能与冷却和压实过程有关。第三，对形变干涉图中的大气延迟异常进行了定量评价。一些干涉图中的大气延迟异常很明显，而且始终小于一到两个条纹的量级。因此，重复观测对于自信地解释与火山活动有关的微小地球物理信号很重要。最后，利用双程差分干涉法，我们分析了先发式膨胀、强迫收缩和后发式膨胀，并用独立的图像对验证了观测结果。我们观察到了与1997年喷发相关的140多厘米的下沉。这次下沉发生在喷发前16个月到喷发后5个月之间，在此之前，1992年至1995年期间，以同一地点为中心的∼上升了18厘米，随后，在1997年9月至1998年期间，∼上升了10厘米。最好的模型表明，岩浆储集层位于火山口中心以下2.7公里处，距离喷口∼5公里。我们估计喷发物质的体积为0.055千米3，喷发熔岩的平均厚度为∼7.4m。
ERS-1/ERS-2 synthetic aperture radar interferometry was used to study the 1997 eruption of Okmok volcano in Alaska. First, we derived an accurate digital elevation model (DEM) using a tandem ERS-1/ERS-2 image pair and the preexisting DEM. Second, by studying changes in interferometric coherence we found that the newly erupted lava lost radar coherence for 5–17 months after the eruption. This suggests changes in the surface backscattering characteristics and was probably related to cooling and compaction processes. Third, the atmospheric delay anomalies in the deformation interferograms were quantitatively assessed. Atmospheric delay anomalies in some of the interferograms were significant and consistently smaller than one to two fringes in magnitude. For this reason, repeat observations are important to confidently interpret small geophysical signals related to volcanic activities. Finally, using two-pass differential interferometry, we analyzed the preemptive inflation, coeruptive deflation, and posteruptive inflation and confirmed the observations using independent image pairs. We observed more than 140 cm of subsidence associated with the 1997 eruption. This subsidence occurred between 16 months before the eruption and 5 months after the eruption, was preceded by ∼18 cm of uplift between 1992 and 1995 centered in the same location, and was followed by ∼10 cm of uplift between September 1997 and 1998. The best fitting model suggests the magma reservoir resided at 2.7 km depth beneath the center of the caldera, which was ∼5 km from the eruptive vent. We estimated the volume of the erupted material to be 0.055 km3 and the average thickness of the erupted lava to be ∼7.4 m.