Faults and ground uplift at active calderas
Faults and ground uplift at active calderas
复制标题
活动火山口的断层和地面隆起
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
J. Gottsmann
中科院分区：
文献类型：
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作者：
A. Folch;J. Gottsmann
摘要地下体积和压力的增加触发表面膨胀在活跃的破火山口一般推导出反演地面变形时间序列使用各向同性和均匀半空间模型（IHM）。这些模型代表了地壳力学行为的简化数学模拟。使用三维数值模拟，我们表明，横向不连续性，如火山口内或火山口环断层可以显着放大和扭曲的地面变形模式在动荡。因此，不考虑横向不连续性的使用IHM的数据反演可以提供关于起因源参数的错误结果。我们还发现，放大和失真的程度在位移/距离梯度在断层附近的突变的形式是依赖于源的几何形状。扁长天体代表了一种特别关键的几何形状，其压力增加可能被高估了三倍。我们的3D分析表明，放大效应可能比早期的2D模型预测的要大得多。我们验证了理论结果，通过应用我们的模型来研究边界断层和源的几何形状在Campi Flegrei（意大利）和Sierra Negra（加拉帕戈斯群岛，厄瓜多尔）不安分的破火山口地面隆起过程中的位移场的影响。基于IHMs和我们的数值模型的结果的差异，我们认为，采用IHMs反演地面位移和重力时间序列在某些情况下可能会导致有偏见的评估与地面隆起的危害。
Abstract Subsurface volume and pressure increases triggering surface inflation at active calderas are generally deduced by inverting ground-deformation time-series using isotropic and homogeneous half-space models (IHM). These models represent simplified mathematical analogues of the mechanical behaviour of the Earth’s crust. Using three-dimensional numerical modelling, we show that lateral discontinuities such as intracaldera- or caldera-ring-faults can significantly amplify and distort the ground deformation pattern during unrest. As a consequence, data inversions using IHMs, which do not consider lateral discontinuities, can provide erroneous results on causative source parameters. We also find that the degree of amplification and distortion in the form of abrupt changes in displacement/distance gradients in proximity to faults is dependent on source geometry. Prolate bodies represent a particularly critical geometry for which pressure increases may be overestimated by a factor of up to three. Our 3D analysis suggests that amplification effects can be much larger than predicted by earlier 2D models. We validate theoretical results by applying our model to investigate the effect of boundary faults and source geometries on the displacement field during ground uplift at the restless calderas of Campi Flegrei (Italy) and Sierra Negra (Galapagos Islands, Ecuador). Based on the discrepancy in results from IHMs and our numerical model, we argue that employing IHMs for inversion of ground displacement and gravity time-series may in some cases lead to a biased assessment of hazards associated with ground uplift.