Cyclical geothermal unrest as a precursor to Iceland's 2021 Fagradalsfjall eruption
Cyclical geothermal unrest as a precursor to Iceland's 2021 Fagradalsfjall eruption
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DOI：
10.1038/s41561-022-00930-5
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发表时间：
2022-05-02
影响因子：
18.3
通讯作者：
Milkereit, Claus
中科院分区：
文献类型：
--
作者：
Flovenz, Olafur G.;Wang, Rongjiang;Milkereit, Claus
了解和约束火山区大地形变的来源是危险评估的一个重要组成部分。在这里，我们分析了2021年3月冰岛Fagradalsfjall火山喷发前一年的形变和地震活动。我们使用光缆记录生成了39,500次地震的高分辨率目录，并开发了一个孔洞弹性模型来描述喷发点以西8公里处的Svartsengi地热田的三个喷发前隆升和沉降旋回。我们发现，观测到的形变最好的解释是在地热场以下4公里处注入总体积为0.11+/-0.05公里(3)、密度为850+/-350 kg m(-3)的流体对渗透性含水层的周期性侵入。因此，我们认为岩浆二氧化碳的侵入可以解释大地测量、重力和地震数据，尽管不能排除岩浆的一些贡献。根据结合孔洞弹性模型的39,500个前兆地震目录，岩浆气体侵入地热含水层产生了周期性变形，并为2021年冰岛Fagradalsfjall喷发奠定了基础。
Understanding and constraining the source of geodetic deformation in volcanic areas is an important component of hazard assessment. Here, we analyse deformation and seismicity for one year before the March 2021 Fagradalsfjall eruption in Iceland. We generate a high-resolution catalogue of 39,500 earthquakes using optical cable recordings and develop a poroelastic model to describe three pre-eruptional uplift and subsidence cycles at the Svartsengi geothermal field, 8 km west of the eruption site. We find the observed deformation is best explained by cyclic intrusions into a permeable aquifer by a fluid injected at 4 km depth below the geothermal field, with a total volume of 0.11 +/- 0.05 km(3) and a density of 850 +/- 350 kg m(-3). We therefore suggest that ingression of magmatic CO2 can explain the geodetic, gravity and seismic data, although some contribution of magma cannot be excluded.Ingression of magmatic gas into a geothermal aquifer generated cyclical deformation and primed the system for the 2021 Fagradalsfjall eruption, Iceland, according to a catalogue of 39,500 precursory earthquakes combined with a poroelastic model.