Volcanoes undergoing unrest often produce displacements at the ground surface, providing an important window to interpret the dynamics of the underlying magmatic system. The thermomechanical properties of the surrounding host rock are expected to be highly heterogeneous, with key physical parameters having a strong dependence on temperature. Deformation models that incorporate nonelastic rheological behaviors are therefore heavily reliant on the assumed thermal conditions, and so it is critical to understand how the thermomechanical crustal structure affects the observed deformation field. Here, we use a series of thermo-viscoelastic Finite Element models to explore how variations in thermal constraints (i.e., reservoir temperature and background geothermal gradient) affect surface displacement patterns when using the Maxwell and Standard Linear Solid (SLS) viscoelastic configurations. Our results demonstrate a strong variability in the viscoelastic deformation response when changing the imposed thermal constraints, caused by the partitioning of deformation and the dissipation of induced stresses. When using the SLS rheology, we identify that cumulative long-term displacements can vary by over 20%, relative to a reference model with a reservoir temperature of 900°C and background geothermal gradient of 30 K km⁻¹. The relative change increases to a maximum of 35% when thermal weakening of the Young's modulus is also considered. Contrastingly, the deformation patterns of the Maxwell rheology are governed by unbounded displacements and complete stress relaxation. Ultimately, we outline that uncertainties in the thermal constraints can have a significant impact on best-fit source parameters (e.g., size and depth) and overpressure/volume-change loading histories inferred from thermo-viscoelastic models.

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探索热控地壳粘度对火山地表变形的影响

经历动荡的火山经常在地表产生位移，为解释下伏岩浆系统的动力学提供了一个重要的窗口。预计周围主岩的热力学性质是高度非均质的，关键物理参数对温度有很强的依赖性。因此，包含非弹性流变行为的变形模型严重依赖于假设的热条件，因此了解热机械地壳结构如何影响观察到的变形场至关重要。在这里，我们使用一系列热粘弹性有限元模型来探索热约束（即，当使用麦克斯韦和标准线性实体 (SLS) 粘弹性配置时，储层温度和背景地热梯度会影响地表位移模式。我们的结果表明，当改变强加的热约束时，粘弹性变形响应有很大的可变性，这是由变形的分配和诱导应力的耗散引起的。使用 SLS 流变学时，我们发现，相对于具有 900°C 储层温度和 30 K km 背景地温梯度的参考模型，累积长期位移可能变化超过 20% 由变形的分配和诱导应力的耗散引起。使用 SLS 流变学时，我们发现，相对于具有 900°C 储层温度和 30 K km 背景地温梯度的参考模型，累积长期位移可能变化超过 20% 由变形的分配和诱导应力的耗散引起。使用 SLS 流变学时，我们发现，相对于具有 900°C 储层温度和 30 K km 背景地温梯度的参考模型，累积长期位移可能变化超过 20%^-1。当还考虑杨氏模量的热弱化时，相对变化增加到最大 35%。相比之下，麦克斯韦流变学的变形模式受无界位移和完全应力松弛控制。最后，我们概述了热约束的不确定性可能对最佳拟合源参数（例如，尺寸和深度）和从热粘弹性模型推断出的超压/体积变化加载历史产生重大影响。