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首页> 外文期刊>Journal of geophysical research. Solid earth: JGR >Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets
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Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

机译：圣海伦斯山的火山穹顶动力学：通过地震活动和照相机图像像素偏移监控变形和间歇沉降

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摘要

The surface deformation field measured at volcanic domes provides insights into the effects of magmatic processes, gravity-and gas-driven processes, and the development and distribution of internal dome structures. Here we study short-term dome deformation associated with earthquakes at Mount St. Helens, recorded by a permanent optical camera and seismic monitoring network. We use Digital Image Correlation (DIC) to compute the displacement field between successive images and compare the results to the occurrence and characteristics of seismic events during a 6 week period of dome growth in 2006. The results reveal that dome growth at Mount St. Helens was repeatedly interrupted by short-term meter-scale downward displacements at the dome surface, which were associated in time with low-frequency, large-magnitude seismic events followed by a tremor-like signal. The tremor was only recorded by the seismic stations closest to the dome. We find a correlation between the magnitudes of the camera-derived displacements and the spectral amplitudes of the associated tremor. We use the DIC results from two cameras and a high-resolution topographic model to derive full 3-D displacement maps, which reveals internal dome structures and the effect of the seismic activity on daily surface velocities. We postulate that the tremor is recording the gravity-driven response of the upper dome due to mechanical collapse or depressurization and fault-controlled slumping. Our results highlight the different scales and structural expressions during growth and disintegration of lava domes and the relationships between seismic and deformation signals.
机译：在火山穹顶处测量的表面形变场提供了对岩浆过程，重力和气体驱动过程以及内部穹顶结构的发育和分布的影响的洞见。在这里，我们研究由永久性光学摄像机和地震监测网络记录的与圣海伦斯山地震相关的短期穹顶变形。我们使用数字图像相关性（DIC）计算连续图像之间的位移场，并将结果与​​2006年圆顶增长6周期间地震事件的发生和特征进行比较。结果表明，圣海伦斯山的圆顶增长圆顶表面的短期米级向下位移反复中断了该位移，这些位移及时与低频，大震级地震事件以及随后的类似震颤信号相关。地震仅由距圆顶最近的地震台记录。我们发现相机产生的位移的幅度与相关震颤的频谱幅度之间存在相关性。我们使用两台摄像机的DIC结果和高分辨率地形图模型得出完整的3-D位移图，该图揭示了内部穹顶结构以及地震活动对日表面速度的影响。我们假定，由于机械坍塌或降压以及断层控制的坍塌，地震记录了上穹顶的重力驱动响应。我们的结果突出了熔岩穹顶的生长和崩解以及地震信号和变形信号之间的关系期间的不同尺度和结构表达。

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