A Model Experiment of Fracture Induced Long‐Period Events: Injection of Pressurized Gas Into a Viscoelastic Rock Analog
A Model Experiment of Fracture Induced Long‐Period Events: Injection of Pressurized Gas Into a Viscoelastic Rock Analog
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断裂诱发长周期事件的模型实验：将加压气体注入粘弹性岩石模拟中
DOI：
10.1029/2019gl085009
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发表时间：
2019
影响因子：
5.2
通讯作者：
Tsutsui Ryo
中科院分区：
文献类型：
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作者：
Namiki Atsuko;Takahashi Makoto;Tsutsui Ryo
在潜水或蒸汽岩浆喷发之前，在火山地区观察到的低频事件可能是由加压气体注入受损/加热的岩石或凝固的岩浆激发的。为了模拟这一过程，我们进行了一系列的气体注入实验，凝胶作为模拟这样的软岩。当我们将压缩空气注入具有较高和较低剪切模量的准麦克斯韦流体时，分别出现裂纹或塞。裂纹扩展速度由凝胶的剪切波速度组成。在裂纹产生之初，出现多个裂纹，产生脉冲状低频信号。相反，段塞的增长速度比剪切波速度快，并激发高频振荡。这些结果表明，在火山地区观察到的低频地震活动不仅是裂纹共振的结果，也是软岩中裂纹扩展的结果。
Low‐frequency events observed in volcanic areas preceding phreatic or phreatomagmatic eruptions may be excited by the injection of pressurized gas into damaged/heated rocks or solidifying magmas. To simulate this process, we conducted a series of gas injection experiments in gels as an analog of such soft rocks. When we inject the pressurized air into a quasi‐Maxwell fluid with higher and lower shear moduli, cracks or a slug appears, respectively. The crack propagation velocity consists of the shear wave velocity of the gel. At the beginning of the crack generation, multiple cracks emerge, causing pulse‐like low‐frequency signals. In contrast, the slug grows faster than the shear wave velocity and excites high‐frequency oscillation. These results show the possibility that the low‐frequency seismicity observed in volcanic regions is the result of not only the resonance of a crack but also the crack propagation in soft rocks.