Volcanoes in extensional environments may show gradual subsidence over decades during quiescent periods, due to various processes such as magma withdrawal, cooling, contraction, plate spreading and viscoelastic response. If significant rheological anomalies reside in volcano roots, due to the presence of magma and hot rock, they can influence the style of deformation. We use Finite Element Method (FEM) models to explore how strain localization due to extension can lead to volcano deflation. We apply rheological models comprising an elastic layer overlying a viscoelastic domain and include local up-doming regions of low viscosity material beneath volcanic centers. The models reveal a localized subsidence above the rheological anomaly, influenced by the tectonic extension, and by the up-doming volume and its viscosity. The models suggest that plate divergence may account for 4–5 mm/yr of observed subsidence at Krafla and Askja volcanic systems (KVS and AVS, respectively) in North Iceland.

中文翻译：

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正在延伸的火山的应变定位：冰岛北部 Krafla 和 Askja 火山系统长期变形的研究


由于岩浆抽取、冷却、收缩、板块扩散和粘弹性响应等各种过程，伸展环境中的火山可能会在静止期的几十年内逐渐沉降。如果火山根部存在明显的流变异常，由于岩浆和热岩石的存在，它们会影响变形的类型。我们使用有限元法 （FEM） 模型来探索由于拉伸引起的应变定位如何导致火山通缩。我们应用了流变模型，该模型由覆盖在粘弹性域上的弹性层组成，并包括火山中心下方低粘度材料的局部凸起区域。这些模型揭示了流变异常上方的局部沉降，受构造延伸、隆起体积及其粘度的影响。这些模型表明，板块散度可能是在冰岛北部的 Krafla 和 Askja 火山系统（分别为 KVS 和 AVS）观察到的 4-5 毫米/年沉降的原因。