Hayer C, Burton M, Ferrazzini V, Esse B, Di Muro A
COMET, Department of Earth and Environmental Sciences, The University of Manchester, Manchester, M13 9PL UK.
Institut de Physique du Globe de Paris, Université de Paris, CNRS, 75005 Paris, France.
Bull Volcanol. 2023;85(4):21. doi: 10.1007/s00445-023-01628-1. Epub 2023 Mar 8.
Piton de la Fournaise volcano, La Réunion, France, erupted between the 2 and 6 April 2020, one of a series of eruptive phases which occur typically two or three times per year. Here, we use back trajectory analysis of satellite data from the TROPOMI instrument to determine that gas emissions during the June 2020 eruption were of unusually high intensity and altitude, producing 34.9 ± 17.4 kt of SO and plume heights up to 5 km a.s.l. The early stages of the eruption (2-4 April 2020) were characterised by relatively low SO emission rates despite strong low frequency tremor (LFT); the latter phase followed an increase in intensity and explosivity in the early hours of 5 April 2020. This period included lava fountaining, significantly increased SO emission rates, increased high frequency tremor (HFT) and decreased LFT. Using the PlumeTraj back trajectory analysis toolkit, we found the peak SO emission rate was 284 ± 130 kg/s on the 6 April. The plume altitude peaked at ~ 5 km a.s.l. on 5 April, in the hours following a sudden increase in explosivity, producing one of the tallest eruption columns recorded at Piton de la Fournaise. PlumeTraj allowed us to discriminate each day's SO, which otherwise would have led to a mass overestimate due to the plumes remaining visible for more than 24 h. The eruption exhibited a remarkable decoupling and anti-correlation between the intensity of the LFT signal and that of the magma and gas emission rates. LFT intensity peaked during the first phase with low magma and SO emissions, but quickly decreased during the second phase, replaced by unusually strong HFT. We conclude that the observation of strong HFT is associated with higher intensity of eruption, degassing, and greater height of neutral buoyancy of the plume, which may provide an alert to the presence of greater hazards produced by higher intensity eruptive activity. This might be particularly useful when direct visual observation is prevented by meteorological conditions. This eruption shows the importance of combining multiple data sets when monitoring volcanoes. Combining gas and seismic data sets allowed for a much more accurate assessment of the eruption than either could have done alone.
The online version contains supplementary material available at 10.1007/s00445-023-01628-1.
法国留尼汪岛的富尔奈斯火山于2020年4月2日至6日喷发，这是通常每年发生两到三次的一系列喷发阶段之一。在此，我们利用TROPOMI仪器的卫星数据进行后向轨迹分析，以确定2020年6月喷发期间的气体排放强度和高度异常高，产生了34.9±17.4千吨的二氧化硫，羽流高度达海拔5千米。喷发的早期阶段（2020年4月2日至4日）尽管低频震颤（LFT）强烈，但二氧化硫排放率相对较低；后期阶段在2020年4月5日凌晨强度和爆炸性增加。这一时期包括熔岩喷泉、二氧化硫排放率显著增加、高频震颤（HFT）增加以及低频震颤减少。使用PlumeTraj后向轨迹分析工具包，我们发现4月6日的二氧化硫排放峰值率为284±130千克/秒。羽流高度在4月5日达到峰值，海拔约5千米，在爆炸性突然增加后的数小时内，形成了富尔奈斯火山记录到的最高喷发柱之一。PlumeTraj使我们能够区分每天的二氧化硫排放情况，否则由于羽流在超过24小时内仍可见，会导致质量高估。这次喷发在低频震颤信号强度与岩浆和气体排放率之间表现出显著的解耦和反相关。低频震颤强度在第一阶段达到峰值，此时岩浆和二氧化硫排放量较低，但在第二阶段迅速下降，取而代之的是异常强烈的高频震颤。我们得出结论，强烈高频震颤的观测与更高强度的喷发、脱气以及羽流中性浮力高度相关，这可能为更高强度喷发活动产生的更大危害提供警报。当气象条件阻碍直接目视观测时，这可能特别有用。这次喷发表明在监测火山时结合多个数据集的重要性。结合气体和地震数据集比单独使用任何一个数据集都能更准确地评估喷发情况。
在线版本包含可在10.1007/s00445-023-01628-1获取的补充材料。
