5:15 PM - 7:15 PM
[SVC32-P14] Studies on the generation process of T-type earthquakes at Asama volcano in Japan in 2023
Keywords:Volcanic earthquake, T-type earthquake, Asama volcano, Crack resonance
In this study, I investigated T-type seismic events occurred at Asama volcano, Japan in March and July of 2023 with hypocenter determination, waveform inversion, spectrum analysis, and estimation of oscillation source in order to understand the excitation field of T-type earthquakes and the generation process there, and to clarify the relationship between T-type earthquakes activity and volcanic activity. The results show that the hypocenters of the T-type earthquakes were located at an elevation of 1.5-2.0 km just below the Kamayama crater, and characteristic coda waves could be explained by the volumetric change of cracks. The predominant frequency and quality factor Q of the T-type earthquakes and their temporal changes can be interpreted as reflecting changes in gas weight fraction and volume in fluid filled crack with a misty gas (mixture of small water droplets and water vapor). The enhancement of T-type seismicity that preceded tilt change suggests that volcanic gases bubbling and separating from the magma in the deep part of the volcano increased the pressure in the conduit under the crater and opened the crack prior to the ascent of the deep magma. Through this study, it is possible to estimate the state of the inner volcanic fluid and the conditions of the conduit by monitoring and analyzing T-type seismic activity. This study was supported by ERI JURP 2024-D-07 in Earthquake Research Institute, the University Tokyo.