3D study of dyke-induced asymmetric graben: The 1971 Mt. Etna (Italy) case by structural data and numerical modelling

IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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Abstract

In this work, we have integrated field data and numerical models to characterise a unique dyke-induced graben system, exposed both in section and plan view, with an unexpected asymmetric fault geometry. This volcanotectonic feature is related to the 1971 eruption of Mt. Etna (southern Italy) and is located near the northern wall of the Valle del Bove, a huge depression carved into the eastern flank of the edifice. A new structural map and quantitative data were obtained from the analysis of aerial stereophotos collected before the onset of the 1971 eruption and after, high-resolution drone-derived models and field surveys carried out in the summer of 2022. In plan view, the graben is 2-km-long and its width ranges 27–143 m from the bottom to the upper part of the section view, with about 82 m of difference in elevation from top to bottom. Graben faults clearly show an asymmetric setting in terms of attitude, with one fault that dips 70° to the south, and the other one that dips 50° to the north. Vertical offset values are greater at higher elevations. We also ran a set of numerical models, aimed at investigating the distribution and orientation of stresses around the inferred dyke tip and in the host rock. The comparison between field data and numerical models suggests a key role of the inclined topography, as shown in section view, in determining the orientation of dyke-induced σ1 and σ3 in the host rock. This, in turn, controls the geometry of the graben faults, resulting in the observed asymmetric setting. Additionally, dyke-induced stress concentrations and vertical offset values support the hypothesis of a downward propagation of the graben faults, from the surface down to the dyke tip.

堤坝诱发非对称地堑的三维研究:通过结构数据和数值建模研究 1971 年埃特纳火山(意大利)案例
在这项研究中,我们综合了实地数据和数值模型,描述了一个独特的堤坝诱发的地堑系统的特征,该地堑在剖面图和平面图上都有暴露,具有意想不到的非对称断层几何形状。这一火山构造特征与 1971 年埃特纳火山(意大利南部)的喷发有关,位于 Valle del Bove 北壁附近,这是一个巨大的洼地,雕刻在埃特纳火山的东侧。通过分析 1971 年火山爆发前和爆发后收集的航空立体照片、高分辨率无人机模型以及 2022 年夏季进行的实地勘测,获得了新的结构图和定量数据。从平面图上看,地堑长 2 公里,从底部到剖面图上部的宽度为 27-143 米,上下高差约 82 米。地堑断层的姿态明显不对称,一条断层向南倾斜 70°,另一条向北倾斜 50°。海拔越高,垂直偏移值越大。我们还运行了一套数值模型,旨在研究推断出的堤坝顶端周围和主岩中的应力分布和方向。实地数据与数值模型之间的比较表明,倾斜地形(如剖面图所示)在决定堤坝引起的σ1和σ3在母岩中的走向方面起着关键作用。这反过来又控制了地堑断层的几何形状,导致了观察到的不对称设置。此外,堤坝诱发的应力集中和垂直偏移值支持了地堑断层从地表向下延伸至堤坝顶端的假设。
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来源期刊
Journal of Structural Geology
Journal of Structural Geology 地学-地球科学综合
CiteScore
6.00
自引率
19.40%
发文量
192
审稿时长
15.7 weeks
期刊介绍: The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.
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