09:00 〜 09:15
[SVC29-01] ひまわり８号画像による2018年新燃岳・2019年ベズィミアニ噴火の高頻度赤外観測
キーワード：火山、噴火、衛星、リモートセンシング
Discrete explosive eruptions, including Vulcanian explosions, occur at various stages in the effusive activity of viscous lava. However, the differences in occurrence time and mechanisms are not yet well understood and categorized. We investigated the 2018 Shinmoe-dake eruption by high-frequency infrared observation using Himawari-8 and the 2019 Bezymianny eruption for comparison. Each stage of the 2018 Shinmoe-dake activity shows characteristic thermal variations: the ash-plume emission stage has no thermal anomalies; the lava effusion stage has constant high thermal anomalies; the Vulcanian eruption stage has a series of spike-like thermal anomalies. The occurrence times of individual spike-like thermal anomalies coincide with the onset of Vulcanian eruptions. On the short time scale, they consist of the thermal anomaly rising sharply and decreasing gradually, corresponding to the explosion's ejection of hot materials and the subsequent cooling. Vulcanian eruption of the 2018 Shinmoe-dake activity is characterized by the absence of thermal anomalies in the precursory period, showing an asymmetric thermal pulse with no precursory anomaly because of no precursory lava or gas discharge. In the 2019 Bezymianny activity, the level of the thermal anomaly increased with lava effusion; during this, an explosive eruption occurred, and the thermal anomaly peaked, after which it decreased due to the cooling of the ejecta, thereby showing a symmetric thermal pulse involving the precursory anomaly. Accordingly, two types of explosive eruptions can be recognized. One occurs after lava effusion activity (post-effusion type explosion), showing an asymmetric thermal pulse. The other occurs in the middle of the lava effusion activity (syn-effusion type explosion), resulting in a symmetric thermal pulse. The difference is possibly related to the efficiency of releasing volatile components from the effusing magma. High-density thermal observations from the Himawari 8/9 images provide an effective way to investigate the diversity of such eruption sequences.