[M-IS04] Interdisciplinary studies on pre-earthquake processes

[MIS04-P13] Monitoring volcanic lava activity at the Mt Shinmoedake using Himawari
AHI data: Spatiotemporal variation of surface temperature before lava
eruption

*Kitade Akitugu¹, Chie Yoshino¹, syu kaneko¹, Katsumi Hattori¹ (1.chiba university)

Ground-based monitoring of volcanoes is not possible for all active volcanoes due to topographical constraints and cost. On the other hand, however, volcanic activities involving lava eruptions that result in large human and economic eruptions are usually accompanied by an increase in surface temperature, which makes monitoring surface temperatures by satellite remote sensing effective. Therefore, we have been developing algorithms to detect temperature anomalies associated with volcanic activities (especially monitoring lava activities that cause serious damage to human life and predicting pyroclastic flows) by spatio-temporal analysis of ground surface temperature around volcanoes using nighttime thermal infrared data onboard satellites. A third-generation geostationary meteorological satellite, Himawari-8, is considered to be very effective for volcano monitoring. Himawari-8 has the characteristics of being in a geostationary orbit and being able to observe the same area at all times. It has significant functional improvements over the performance of conventional meteorological satellites in terms of observation wavelength, spatial resolution, and frequency of observations. In addition, third-generation geostationary meteorological satellites with the same characteristics as Himawari-8 have been launched in the United States, China, South Korea, and Europe, and the possibility of global volcano monitoring is expected using these geostationary meteorological satellites. Therefore, it is very meaningful to be the first in the world to build an algorithm for volcano monitoring using Himawari-8 data.
In this study, analysis was conducted for the 2018 eruption activity of Mt. Shinmoe, located on the border between Miyazaki and Kagoshima prefectures. For the analysis, we used thermal infrared data from the Advanced Himawari Imager (AHI) onboard the geostationary meteorological satellite Himawari-8 to perform spatio-temporal statistical analysis of ground surface temperature around the volcano to detect temperature anomalies associated with volcanic activity earlier. In the analysis of surface temperature, 3.9 μm data were used in the analysis to detect small amounts of heat sources. In the time series analysis, differential values at certain distances in the east-west and north-south directions were used to remove seasonal variations and to capture the heat increase due to volcanic activity. In this analysis, accurate rejection of cloud pixels is essential, and we used three brightness temperature difference values (BTD: Brightness Temperature Difference) (Band 14-Band 9, Band 14-Band 15, Band 7-Band 14) to determine the characteristics of each BTD The cloud pixel rejection was performed by considering the characteristics of each BTD. In order to improve the accuracy of the cloud pixel rejection method in Japan, it is important to fuse Lidar data (National Institute for Environmental Studies) and Himawari-8 AHI data at eight locations in Japan (Sapporo, Niigata, Toyama, Tsukuba, Tokyo, Matsue, Nagasaki, and Hendo), determine the threshold value of each BTD for cloud discrimination, and perform cloud discrimination in volcanic regions based on this threshold value. It was found that it is important to determine the threshold of each BTD for cloud discrimination and to perform cloud discrimination in volcanic regions based on the threshold values. For the determination of surface temperature anomalies, a standardized annual surface temperature model was created. The model was created using ±15-day moving average and median values. As a result, we were able to confirm ground surface temperature anomalies associated with magma eruptions and the appearance of lava domes. We were also able to confirm surface temperature anomalies prior to the JMA announcement.