The thermal signature of Aso Volcano during unrest episodes detected from space and ground-based measurements
The thermal signature of Aso Volcano during unrest episodes detected from space and ground-based measurements
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DOI：
10.1186/s40623-018-0831-7
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发表时间：
2018-04-26
影响因子：
3
通讯作者：
Laiolo, Marco
中科院分区：
文献类型：
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作者：
Cigolini, Corrado;Coppola, Diego;Laiolo, Marco
通过将MODIS-MIROVA数据集（2000-2017年）与高分辨率图像（LANDSAT 8 OLI和Sentinel 2）和地基热观测（2013-2017年）相结合，分析了阿索火山（Nakadake）在动荡时期的热特征。主要活动地点（1号火山口）位于火山山顶，由一个火山口（位于南部地区）和一个酸性湖（在斯特龙博利期被一个中央坑取代）组成。在参考期内，由夜间卫星数据获得的火山辐射功率（VRP）主要低于3兆瓦。这一热阈值标志着从高火山活动（HFA）到斯特龙博利火山喷发（SE）的转变。然而，以零星的潜水喷发（PE，最终轴承phreatomagmatic插曲）为特征的时期，这是动荡时期的普遍阶段，表现出非常低的VRP值，约为0.5兆瓦，或更低。卫星数据的统计分析表明，当VRP值高于引用的3 MW阈值时，就会发生从HFA到Strombolian活动的转变（始于2014年8月，于2015年5月停止）。特别是在显著的斯特龙博利阶段（2014年11月至12月），辐射功率高于4兆瓦，达到峰值高达15.6兆瓦（2014年12月7日，即，11月27日斯特龙博利安大爆炸后10天）。相反，地面测量结果表明，前视红外T440 Therm-ocamera在南部地区的Mecolole场记录的热通量在2015年2月之前一直相对稳定在2兆瓦左右。它们的表观温度在斯特龙博利亚大爆炸事件之前在490-575摄氏度左右波动，而在活跃的喷口（称为中央坑）记录的温度最高达到略高于600摄氏度;然后在接下来的几天里都呈现出下降趋势。在斯特龙博利活动期间，火山口湖干涸，然后在2016年7月初补充。然后，火山活动又回到潜水-潜水岩浆活动，完成了喷发循环。在此期间，MIROVA系统探测到的热警报很少，地面测量值在1兆瓦左右波动。最猛烈的爆炸发生在2016年10月8日，在接下来的几周内，测量的VRP略高于2兆瓦。这是与南部地区的热增加，温度远高于300摄氏度。对阿索火山的热监测是火山监测的一个额外工具，可能有助于近实时的危险评估。
The thermal signature of Aso Volcano (Nakadake) during unrest episodes has been analyzed by combining the MODIS-MIROVA data set (2000-2017) with high-resolution images (LANDSAT 8 OLI and Sentinel 2) and ground-based thermal observations (2013-2017). The site of major activity (crater 1) is located at the summit of the volcano and is composed by a fumarole field (located in the South Area) and an acidic lake (replaced by a Central Pit during Strom-bolian phases). The volcanic radiative power (VRP) obtained by nighttime satellite data during the reference period was mainly below 3 MW. This thermal threshold marks the transition from high fumarole activity (HFA) to Strom-bolian eruptions (SE). However, periods characterized by sporadic phreatic eruptions (PE, eventually bearing phreatomagmatic episodes), which is the prevalent phase during unrest episodes, exhibit very low VRP values, being around 0.5 MW, or below. The statistical analysis of satellite data shows that the transition from HFA to Strombolian activity (which started on August 2014 and ceased in May 2015) occurs when VRP values are above the cited 3 MW threshold. In particular during marked Strombolian phases (November-December 2014), the radiative power was higher than 4 MW, reaching peak values up to 15.6 MW (on December 7, 2014, i.e., 10 days after the major Strombolian explosion of November 27). Conversely, ground-based measurements show that heat fluxes recorded by FLIR T440 Therm-ocamera on the fumarole field of the South Area has been relatively stable around 2 MW until February 2015. Their apparent temperatures were fluctuating around 490-575 degrees C before the major Strombolian explosive event, whereas those recorded at the active vent, named Central Pit, reached their maxima slightly above 600 degrees C; then both exhibited a decreasing trend in the following days. During the Strombolian activity, the crater lake dried out and was then replenished by early July, 2016. Then, volcanic activity shifted back to phreatic-phreatomagmatic and the eruptive cycle was completed. During this period, the MIROVA system detected very few thermal alerts and the ground-based measurements were fluctuating around 1 MW. The most violent explosion occurred on October 8, 2016, and within the following weeks measured VRP were moderately above 2 MW. This is coeval with a thermal increase at the fumarole field of the South Area, with temperatures well above 300 degrees C. Thermal monitoring at Aso Volcano is an additional tool in volcano surveillance that may contribute to near-real-time hazard assessment.