桜島火山における反復地震探査(2010年観測)

Abstract

桜島火山において2010年12月に第二回反復地震探査を実施した。観測点は9割以上が前年の位置に再現され, 観測網全体で南北方向に平均0.1m, 東西方向に平均0.2mの精度で観測点位置の再現がなされた。観測では展開248点中245点で波形の収録が成功した。観測波形の振幅は前年比0.8-1.5倍の範囲内に, 走時差は8ms以内であり, 波形の再現性も良好であった。前年観測記録を基準にした残差記録に現れた残差相は走時1.5-3秒台が多く, 桜島北東部を通過してくる波線に対応する記録によく認められる傾向がある。

The second round of the repetitive seismic experiment was carried out on ecember 2010 in Sakurajima Volcano after an inflation period in June. The temporary seismic network was reconstructed well for the 2009's network within 0.1m northward and 0.2m eastward in the average. The data acquisition was successful in 245 of the 248 deployed stations. The amplitude variation ranged within 0.8 to 1.5 times of the 2009's data and the travel time differences were less than 8ms. The reproduction of the waveform was also successful. The residual seismograms were made and include variation of the phase appearance with referring to the 2009's seismogram at the corresponding station. Most of the variations are found around 1.5 to 3 seconds of the residual seismograms.