The Changbaishan Tianchi intraplate volcano is one of the most active and hazardous volcanoes of NE Asia, characterized by a summit caldera formed after the 946 CE ‘Millennium’ Plinian eruption. From December 2020 to June 2021, the frequency and magnitude of earthquakes at Tianchi were significantly higher than during background periods, with hundreds of earthquakes (46 events per month in average) and reaching a local magnitude of M 3.1. This study reports a comprehensive deformation analysis and geophysical inversion scheme aimed to unveil the dynamics of this period. Multi-temporal InSAR analysis results of 32 ALOS-2 images from 2018 to 2022 show that the surface deformation is a combination of seasonal fluctuations (± 25 mm in average, with a maximum ± 45 mm) and a long-term positive component. The least squares linear regression of the deformation time series and temperature data, isolates the seasonal fluctuations, revealing a clear uplift-subsidence process from June 2020 to July 2021 in the caldera area. To constrain the Tianchi plumbing system dynamics, a combined inversion scheme consisting of three deformation sources is designed. The inversion results and the seismic records indicate that Tianchi volcano has experienced a low-level unrest episode from December 2020 to June 2021. The shallower plumbing system, located at about 5–9 km depth and modelled by pressurized spheroids, underwent a cumulative volume increase of 26 × 10 m from November 2018 to April 2021, followed by a volume decrease of 9 × 10 m from April to July 2021. This suggests magma uprising from the 14 km deep storage zone to the shallower plumbing system, followed by depressurization of the plumbing system due to the escape of fluids. This research provides a comprehensive understanding of the magma and fluid migration dynamics within the Tianchi multi-level plumbing system for the first time.

中文翻译：

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根据ALOS-2/PALSAR-2和地震数据分析2021年长白山天池火山的动乱动态

长白山天池板内火山是东北亚最活跃、最危险的火山之一，其特点是在公元 946 年“千年”普林尼式喷发后形成的山顶破火山口。 2020年12月至2021年6月，天池地震发生频率和震级明显高于背景时期，发生数百次地震（平均每月46次），局地震级达到3.1级。这项研究报告了全面的变形分析和地球物理反演方案，旨在揭示这一时期的动态。 2018年至2022年32幅ALOS-2影像的多时相InSAR分析结果表明，地表变形是季节性波动（平均±25 mm，最大±45 mm）和长期正分量的组合。对变形时间序列和温度数据进行最小二乘线性回归，分离出季节波动，揭示了火山口地区从2020年6月到2021年7月明显的隆起-沉降过程。为了约束天池管道系统动力学，设计了由三个变形源组成的组合反演方案。反演结果和地震记录表明，天池火山在2020年12月至2021年6月期间经历了一次低级动荡。位于约5-9公里深度、以加压球体为模型的较浅的管道系统经历了累积体积增加。从 2018 年 11 月到 2021 年 4 月，体积减少了 26 × 10 m，随后从 4 月到 2021 年 7 月，体积减少了 9 × 10 m。这表明岩浆从 14 km 深的储存区上升到较浅的管道系统，随后岩浆减压由于液体泄漏而导致管道系统损坏。这项研究首次全面了解了天池多层管道系统内的岩浆和流体运移动力学。