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The 2011-2019 Long Valley Caldera inflation: New insights from separation of superimposed geodetic signals and 3D modeling
Earth and Planetary Science Letters ( IF 4.8 ) Pub Date : 2021-06-22 , DOI: 10.1016/j.epsl.2021.117055
F. Silverii , F. Pulvirenti , E.K. Montgomery-Brown , A.A. Borsa , W.R. Neely

Increasingly accurate, and spatio-temporally dense, measurements of Earth surface movements enable us to identify multiple deformation patterns and highlight the need to properly characterize the related source processes. This is particularly important in tectonically active areas, where deformation measurement is crucial for monitoring ongoing processes and assessing future hazard. Long Valley Caldera, California, USA, is a volcanic area where frequent episodes of unrest involve inflation and increased seismicity. Ground- and satellite-based instruments show that volcanic inflation renewed in 2011, and is continuing as of early 2021. Additionally, Long Valley Caldera is affected by the large, but spatially and temporally variable, amounts of precipitation falling on the adjacent Sierra Nevada Range.

The density and long duration of deformation measurements at Long Valley Caldera provide an excellent collection of data to decompose time-series and separate multiple superimposed deformation sources. We analyze Global Navigation Satellite System (GNSS) time-series and apply variational Bayesian Independent Component Analysis (vbICA) decomposition method to isolate inflation-related signals from other processes. We show that hydrological forcing causes significant horizontal and vertical deformation at different temporal (seasonal and multiyear) and spatial (few to hundreds of km) scales that cannot be ignored while analyzing and modeling the tectonic signal. Focusing on the last inflation episode, we then improve on prior simplistic models of the inflation reservoir by including heterogeneous subsurface material properties and topography. Our results suggest the persistence and stability of the reservoir (prolate ellipsoid at about 8 km beneath the resurgent dome) and indicate a 40-50% reduction of the inflation rate after about 3 years from the inflation onset. The onset of the reduced inflation rate corresponded in time with the occurrence of a strong seismic swarm in the Caldera, but also to the temporal variation of climatic conditions in the area.



中文翻译:

2011-2019 Long Valley Caldera 通货膨胀:从叠加大地测量信号和 3D 建模分离的新见解

越来越准确和时空密集的地球表面运动测量使我们能够识别多种变形模式,并强调正确表征相关源过程的必要性。这在构造活跃的地区尤为重要,在这些地区,变形测量对于监测正在进行的过程和评估未来的危险至关重要。美国加利福尼亚州长谷火山口是一个火山区,经常发生动荡,包括通货膨胀和地震活动增加。基于地面和卫星的仪器显示,火山膨胀在 2011 年重新出现,并在 2021 年初持续。此外,长谷火山口受到邻近内华达山脉的大量但在空间和时间上可变的降水量的影响.

Long Valley Caldera 变形测量的密度和长时间持续时间为分解时间序列和分离多个叠加变形源提供了极好的数据集合。我们分析全球导航卫星系统 (GNSS) 时间序列并应用变分贝叶斯独立分量分析 (vbICA) 分解方法将通货膨胀相关信号与其他过程隔离开来。我们表明,水文强迫在不同的时间(季节性和多年)和空间(几到几百公里)尺度上导致显着的水平和垂直变形,在分析和建模构造信号时不可忽视。关注最后的膨胀事件,然后我们通过包括异质地下材料特性和地形来改进膨胀储层的先前简单模型。我们的结果表明储层的持久性和稳定性(在复苏穹顶下方约 8 公里处的长椭球体),并表明从通货膨胀开始大约 3 年后,通货膨胀率降低了 40-50%。通货膨胀率下降的开始与火山口发生强烈地震群的时间相对应,但也与该地区气候条件的时间变化相对应。

更新日期:2021-06-22
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