09:00 〜 09:15
[SVC31-01] Infrasonic source height constraint using a very-small-aperture array
キーワード：空振、アレイ、火山
The infrasonic source height is essential to understand the source mechanisms, such as the explosion at the vent or the volcanic jet above the vent. Yamakawa et al. (2022) tried to estimate the source height using a very-small-aperture three-dimensional array (20 m aperture and 2 m height) at the summit of Stromboli Volcano, Italy, in June 2019. Then, the array analysis unexpectedly estimated the frequency dependence of BEL (back elevation) and slowness with sufficient certainty. To investigate it, this study conducted the numerical simulation of the acoustic propagation using COMSOL Multiphysics 5.6. It revealed that the wavenumber vector near the rigid ground is parallel to the ground dip due to the wave reflection, indicating that we should fix the BEL at the ground dip and estimate the slowness. It was found that the frequency dependence of the apparent slowness was generated by the topographic effect. Particularly, the diffraction at the summit behind the array was significant. Comparing the simulation and observation results constrained the source height within 60 m above the source. More specifically, the simulation with a source height of 20-30 m explained the observation best, though the topographic uncertainty left the possibility that the source was at the vent (0-m high).