Nishimura Takeshi, Emoto Kentaro, Nakahara Hisashi, Miura Satoshi, Yamamoto Mare, Sugimura Shunsuke, Ishikawa Ayumu, Kimura Tsunehisa
Department of Geophysics, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-8578, Japan.
Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-8578, Japan.
Sci Rep. 2021 Mar 18;11(1):6319. doi: 10.1038/s41598-021-85621-8.
We present one of the first studies on source location determination for volcanic earthquakes and characterization of volcanic subsurfaces using data from a distributed acoustic sensing (DAS) system. Using the arrival time difference estimated from well-correlated waveforms and a dense spatial distribution of seismic amplitudes recorded along the fiber-optic cable, we determine the hypocenters of volcanic earthquakes recorded at Azuma volcano, Japan. The sources are located at a shallow depth beneath active volcanic areas with a range of approximately 1 km. Spatial distribution of the site amplification factors determined from coda waves of regional tectonic earthquakes are well correlated with old lava flow distributions and volcano topography. Since DAS observation can be performed remotely and buried fiber-optic cables are not damaged by volcanic ash or bombs during eruptions, this new observation system is suitable for monitoring of volcanoes without risk of system damage and for evaluating volcanic structures.
我们展示了首批利用分布式声学传感（DAS）系统的数据进行火山地震震源定位测定及火山地下特征描述的研究之一。通过从相关性良好的波形估计出的到达时间差以及沿光纤电缆记录的地震振幅的密集空间分布，我们确定了日本阿苏山火山记录的火山地震的震源。这些震源位于活跃火山区域下方的浅深度处，范围约为1公里。根据区域构造地震的尾波确定的场地放大因子的空间分布与古老熔岩流分布和火山地形密切相关。由于DAS观测可以远程进行，并且埋入的光纤电缆在火山喷发期间不会受到火山灰或炸弹的破坏，因此这种新的观测系统适用于监测火山而无系统损坏风险，并用于评估火山结构。
