Harmonic tremor model during the 2011 Shinmoe-dake eruption, Japan
Harmonic tremor model during the 2011 Shinmoe-dake eruption, Japan
复制标题
2011 年日本新萌岳喷发期间的谐波震颤模型
DOI：
10.1093/gji/ggaa477
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
M. Takeo
中科院分区：
文献类型：
--
作者：
M. Takeo
新萌岳火山于2011年1月26日至27日开始了三次普林尼式喷发，随后于2011年1月28日至31日进入岩浆喷发阶段，2011年2月1日至10日频繁发生火山喷发。在岩浆喷发和火山喷发阶段，在山顶火山口附近的观测站观测到多次谐波震颤。虽然在世界各地的火山中都观察到了谐波震动，但对震源机制仍然知之甚少。本文提出了一种由弹性通道中的非线性粘性流体流动组成的谐振源模型。一个简单的集总参数模型被用来考虑的过程。动力学描述的三阶系统的常微分方程，使用模型变量的横截面积的收缩段和上游和下游管中的流体速度。该模型产生了各种类型的自维持振荡的轨迹，这些振荡改变了连接在模型上游通道上的储层压力。通过对系统在不动点附近的线性化分析和零倾面的全局分析，定性地揭示了系统自激振荡的机理。为了同时考虑谐波震颤的频率峰值和观测到的相位谱的特性，将观测到的相位图的定性特性与模拟的相位图的定性特性进行比较。该震颤模型模拟了2011年Shinmoe-dake喷发期间观察到的典型谐波震颤的频率峰值和相位图。由于该模型涉及多个几何结构参数，因此具有揭示各种谐波振动震源机制的潜力。
The Shinmoe-dake volcano started with three sub-Plinian eruptions from 26 to 27 January 2011, followed by a magma effusive stage from 28 to 31 January 2011, and Vulcanian eruptions occurred frequently during 1 to 10 February 2011. During the magma effusive and Vulcanian stages, multiple episodes of harmonic tremors were observed at stations near the summit crater. Although harmonic tremors have been observed at various volcanoes worldwide, the source mechanism remains poorly understood. This paper proposes a source model for harmonic tremors, which is composed of a nonlinear viscous fluid flow in a flexible channel. A simple lumped parameter model is used to consider the process. The dynamics are described by a third-order system of ordinary differential equations using model variables for a cross-sectional area of the constricted segment and the fluid velocities in the upstream and downstream tubes. This model produces various kinds of trajectories for self-sustained oscillations that change the reservoir pressure connected on the upstream channel of the model. Linearization analysis around the stationary point and global analysis employing nullcline planes reveal the mechanism of self-sustained oscillations of the system qualitatively. To consider both the frequency peaks of the harmonic tremor and the characteristics of observed phase spectra, the qualitative characteristics of an observed phase portrait are compared to those of a simulated one. This tremor model simulates the frequency peaks and the phase portraits of typical harmonic tremors observed during the 2011 Shinmoe-dake eruption. Because this model involves several geometrical configuration parameters, it has the potential to reveal the source mechanism of various kinds of harmonic tremors.