SeisMic Observations of deep VolcAnic pRocesses

我们的目的是在地震学观测的基础上研究俯冲带火山深部管道系统的喷发前过程。火山是由地幔中产生的融水滋养的，融水通过一个复杂而难以捉摸的管道系统上升到地表，这个管道系统结合了无处不在的集中流动和多层次的水库。火山-岩浆系统的过程可以根据它们的地震表现进行研究。岩浆和气体输送引起的压力变化会产生特定的地震信号，同时围岩中的应力变化也会导致其弹性性质的变化。最大和最危险的火山爆发来自几公里深的岩浆储层。目前，大多数地震观测反映的是浅层的喷发前活动。同时，要充分了解火山系统的功能，发现火山再激活的最早迹象，就需要对火山深层根系的过程进行观察。为此，我们将研究堪察加半岛的克柳切夫斯科伊火山群（KVG），它是世界上最大和最活跃的俯冲火山群，具有系统的深部地震火山活动。拟议的研究将基于对两个主要数据集的分析，这两个数据集完全互补。首先，我们将利用2015-2016年在KVG地区运行的80多台宽带地震仪的大型德法俄联合野外实验KISS数据（Shapiro et al., 2017a），以前所未有的空间覆盖记录2016年Klyuchevskoy火山喷发的准备阶段。我们将把这些数据与俄罗斯合作伙伴在KVG上运行的永久地震台网的长期记录（部分时间为20年）相结合，该台网目前由25个台站组成。该数据集包含了kyuchevskoy、Bezymiammy和Tolbachik三座主要火山的30多次强烈喷发（VEI高达4）的记录，其中大多数都发生在深部地震-火山活动之前。我们将用现代地震学方法分析现有数据，包括时移噪声和基于地震的监测，以及时变地震各向异性的测量。这些调查的结果将反映管道系统的活动及其对地壳力学性质的影响。它们将用于约束和量化基于我们的合作者分析的多孔介质中粘性流动的地球物理流体动力学模型的潜在物理过程。作为主要的科学成果，我们期望建立一个控制岩浆从岩浆系统的深部向地表上升的过程的综合物理模型，以及一套可用于监测这些深部喷发前过程的地震学方法。

We aim to study pre-eruptive processes in the deep parts of plumbing systems in subduction zone volcanoes based on seismological observations. Volcanoes are fed by melts that are generated in the mantle and ascend to the surface through a complex and elusive plumbing system that combines pervasive and focused flows and multi-level reservoirs. The processes in the volcano-magmatic systems can be studied based on their seismological manifestations. Pressure variations caused by magma and gas transport generate specific seismic signals as well as stress variations in the surrounding rock that result in variations of its elastic properties.Largest and most dangerous explosive volcanic eruptions are fed from a few kilometers deep magmatic reservoirs. Currently, most seismological observations reflect the shallow pre-eruptive activity. At the same time fully understanding the functioning of volcanic systems and detecting earliest signs of volcanic re-activation requires observations of the processes in the deep volcanic roots. For this purpose, we will study the Klyuchevskoy Volcanic Group (KVG) in Kamchatka that is the largest and the most active cluster of subduction volcanoes in the world and features the systematic occurrence of deep seismo-volcanic activity.The proposed research will be based on the analysis of two major datasets that perfectly complement each other. First, we will use the data of a large joint German-French-Russian field experiment KISS when more than 80 broadband seismographs operated in the KVG region in 2015-2016 (Shapiro et al., 2017a) and recorded the 2016 Klyuchevskoy eruption including the preparatory phase with unprecedented spatial coverage. We will combine this with the long-term records (partly > 20 years) of the permanent seismic network operated on KVG by our Russian partners, composed today of 25 stations. This dataset contains records of more than 30 strong eruptions (VEI up to 4) of the three major KVG volcanoes: Klyuchevskoy, Bezymiammy, and Tolbachik with most of them being preceded by the deep seismo-volcanic activity.We will analyze the available data with modern seismological methods including time-lapse noise- and earthquake-based monitoring, and measurements of time-variable seismic anisotropy. The results of these investigations will reflect the activity in the plumbing system and its influence on the mechanical properties of the crust. They will be used to constrain and quantify the underlying physical processes based on geophysical fluid dynamics models of viscous flow in porous media analysed by our collaborators. As main scientific results, we anticipate developing a comprehensive physical model of the processes controlling the magma ascent from the deep parts of magmatic systems towards the surface and a set of seismological methods that can be used to monitor these deep-seated pre-eruptive processes.