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| | Abstract | | Seismic reflection surveys at Usu-Showashinzan-Yaneyama was conducted in order to, estimate the shallow structure of the lava-dome base. Four seismic 4 lines were conducted in 2017 and 2018 with 2 lines each two survey lines (Y17 and Y18) were set in the radial direction from the east foot of the lava dome and two (G17 and G18) in tangential direction in the Gurendani on the southeast foot of the lava dome. Both survey lines (Y17, G17) were conducted in 2017 with 24 receivers with using a hammer as the seismic source. The others (Y18, G18) conducted in 2018 with 48 receivers with using a tamping rammer as the seismic source. Split-spread method was applied in all survey lines. The receiver interval was 4m for Y lines and 3m for G lines. As a result of reflection analysis, migrated sections were obtained for all survey lines. The radial sections show an inclined structure that becomes deeper as it moves away from the lava dome, and the tangential sections show a horizontal reflecting surface deeper as it moves away from the lava dome. |
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