[S-VC42] 火山噴火のダイナミクスと素過程

[SVC42-P01] 高圧ガスを粘弾性体に注入する火山性長周期地震のモデル実験

*並木 敦子¹、高橋 真実¹、筒井 稜¹ (1.広島大学　総合科学部)

キーワード：長周期地震、亀裂の伝播、粘弾性

Low-frequency seismic waves are frequently observed in volcanic areas. To understand the source mechanism of such low-frequency signals, we conducted model experiments simulating the volcanic gas injection into a rock. The rocks heated by the ascending magma and hydrothermal fluid may be very hot and damaged, such that their shear wave velocities are low. Similarly, solidifying magmas should have a low shear wave velocity. Our experiments show that the injection of pressurized air into such soft rocks creates multiple cracks and causes pulse-like seismic signals. When the rock analog is further softened, only high-frequency oscillation appears. These results suggest that the low-frequency component observed in the volcanic area before the initiation of eruptions may be the result of crack generation.

Reference:
Namiki, A., Takahashi, M., and Tsutsui, R. (2019), A model experiment of fracture induced long-period events: Injection of pressurized gas into a viscoelastic rock analog. Geophysical Research Letters, 46, 11906-11914.