Two scales of inflation at Lastarria-Cordon del Azufre volcanic complex, central Andes, revealed from ASAR-ENVISAT interferometric data
Two scales of inflation at Lastarria-Cordon del Azufre volcanic complex, central Andes, revealed from ASAR-ENVISAT interferometric data
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ASAR-ENVISAT 干涉数据揭示了安第斯山脉中部拉斯塔里亚-科登德尔阿苏弗雷火山群的两种通货膨胀规模
DOI：
10.1016/j.epsl.2006.12.012
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发表时间：
2007
影响因子：
5.3
通讯作者：
D. Legrand
中科院分区：
文献类型：
--
作者：
J. Froger;D. Remy;S. Bonvalot;D. Legrand
2003年3月至2005年5月在Lastarria-Cordon del Azufre复合体(智利-阿根廷)收集的ASAR-ENVISAT干涉合成孔径雷达(InSAR)数据显示，Pritchard和Simons通过对ERS InSAR数据的分析揭示了2002年大波长地面膨胀的持续性[Nature 418(2002)167-170]。通过数据网络平差和MODIS图像分析相结合的方法减少了对流层对干涉图的贡献，我们得到了一个精确的干涉时间序列，显示了地面位移模式长达2年的时间演变。检测到两个截然不同的充气信号。主信号覆盖一个椭圆形区域，长轴为45公里，短轴为37公里。它与一个区域地貌穹隆相关联。我们估计它的最大通货膨胀率为∼2.5cmyr−1。我们反演了一系列震源几何形状(球形、长椭球体、硬币状裂缝)的干涉合成孔径雷达数据。2003年至2005年期间推断的震源参数与地壳浅至中层(7-15M)的超压储集层一致，平均体积膨胀率约为14×106m3yr−1。除这一主要信号外，ASAR数据突出的一个新特征是位于大波长信号北缘的拉斯塔里亚火山位置的短波长膨胀(6公里宽)。我们用位于拉斯塔里亚火山顶端下方1000米的球形超压源来解释这一短波长信号。我们估计观测期间的平均体积膨胀速率为∼35×103m3yr−1。值得注意的是，在2003年至2005年期间，大的和小的膨胀的体积变化都表现出相同的演化，这表明这两个过程可能是相关的。根据反演结果，结合野外证据和该区数字高程模型的形态构造分析，我们认为深部源区为岩浆成因，浅部源区极有可能与热液有关。在我们的解释中，在Lastarria-Cordon del Azufre火山杂岩观察到的正在进行的变形过程可能代表了一个演化的前火山口硅质系统。将需要进一步的实地地质和地球物理调查，以证实这些假设并完善拟议的模型，主要是基于卫星观测。
ASAR-ENVISAT Interferometric Synthetic Aperture Radar (InSAR) data collected over the Lastarria-Cordon del Azufre complex (Chile–Argentina) between March 2003 and May 2005 show the persistence of the large wavelength ground inflation revealed by Pritchard and Simons in 2002 from the analysis of ERS InSAR data [Nature 418 (2002) 167–170]. After reducing the tropospheric contribution in the interferograms using a combination of data network adjustment and analysis of MODIS images, we produced an accurate interferometric time series showing a 2 yr long temporal evolution of the ground displacements patterns. Two distinct inflating signals are detected. The main signal covers an elliptical area with a 45 km NNE–SSW major axis and a 37 km minor axis. It is correlated with a regional topographic dome. We estimated its maximum inflation rate to ∼2.5 cm yr−1. We inverted the InSAR data for a range of source geometries (spherical, prolate ellipsoids, penny-shaped cracks). The inferred source parameters for 2003–2005 period are consistent with an over-pressured reservoir at shallow to intermediate crustal depths (7–15 km), with an average volumetric rate of inflation of about 14×106m3yr−1. In addition to this main signal a new feature highlighted by the ASAR data is short wavelength inflation (6 km wide) at the location of Lastarria volcano on the northern margin of the large wavelength signal. We explain this short wavelength signal by a spherical over-pressured source lying 1000 m below the summit of Lastarria volcano. We estimate the average volumetric rate of inflation during the observation period to be ∼35×103m3yr−1. It is remarkable that both volumetric variations for the large and small inflations exhibit the same evolution during the 2003–2005 period, suggesting that both processes could be related. On the basis of the inversion results and of arguments provided by field evidences and a morpho-structural analysis of the Digital Elevation Model of the area, we propose that the deep source have a magmatic origin while the shallow source is most likely related to hydrothermal fluids. In our interpretation, the on-going deformation processes observed at Lastarria-Cordon del Azufre volcanic complex could represent an evolving pre-caldera silicic system. Further field geological and geophysical investigations will be required to confirm these hypotheses and refine the proposed model, mostly based on satellite observations.