Hobé Alex, Bazargan Mohsen, Selek Burcu, Tryggvason Ari, Alofe Emmanuel, Gudmundsson Agust
Department of Earth Sciences, Uppsala University, Villavägen 16, Uppsala, 752 36, Sweden.
Department of Earth Sciences, Royal Holloway University of London, Queen's Building, Egham, TW20 0EX, UK.
Sci Rep. 2025 May 12;15(1):16455. doi: 10.1038/s41598-025-95169-6.
Shortly before the 2021 Fagradalsfjall eruption tomographic images indicated a large high V/V anomaly with a top at about 9 km depth directly below the ongoing seismic swarm. Using volcanotectonic principles we interpret this anomaly as part of the roof of a magma reservoir which, furthermore, ruptured on 24 February 2021. The roof rupture resulted in an injected dike-segment propagating vertically at an average rate of about 0.2 m s until it became arrested beneath a stress barrier at ~ 2 km depth, from where the dike-segment propagated laterally. Further magma injections took place, following largely the path of the first dike-segment, resulting in part of the dike reaching outside the stress barrier and propagating vertically as a tiny 'finger' to form a 180-m-long disconnected fissure at the surface on 19 March 2021. The estimated maximum length of the arrested dike is about 9 km, its height 7 km, and its thickness 4 m - in excellent agreement with direct field measurements of basaltic dikes in Iceland. Seismicity also indicates that the same dike path was partly used during the 2022 and 2023 eruptions, in agreement with the location of the resulting volcanic fissures, resulting in the formation of a multiple feeder-dike.
在2021年法格拉达尔火山喷发前不久，层析成像图像显示在持续地震群正下方约9千米深处有一个大型高V/V异常区，其顶部就在此处。运用火山构造原理，我们将这一异常解释为岩浆库顶部的一部分，该岩浆库于2021年2月24日发生破裂。顶部破裂导致一条注入的岩脉段以约0.2米/秒的平均速度垂直向上传播，直至在约2千米深处遇到应力屏障而停止，此后该岩脉段转为横向传播。随后又有岩浆注入，大致沿着第一条岩脉段的路径，致使部分岩脉延伸至应力屏障之外，并于2021年3月19日垂直向上形成一个微小的“指状”，在地表形成一条180米长的不连续裂缝。据估计，受阻岩脉的最大长度约为9千米，高度为7千米，厚度为4米，这与冰岛玄武岩岩脉的实地直接测量结果高度吻合。地震活动还表明，在2022年和2023年的喷发过程中，部分使用了同一条岩脉路径，这与由此产生的火山裂缝位置相符，从而形成了多条供料岩脉。
