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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Modelling of surface stresses and fracturing during dyke emplacement: Application to the 2009 episode at Harrat Lunayyir, Saudi Arabia
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Modelling of surface stresses and fracturing during dyke emplacement: Application to the 2009 episode at Harrat Lunayyir, Saudi Arabia

机译：堤坝筑堤过程中的表面应力和断裂建模：应用于沙特阿拉伯哈拉特·卢纳伊尔2009年集

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Correct interpretation of surface stresses and deformation or displacement during volcanotectonic episodes is of fundamental importance for hazard assessment and dyke-path forecasting. Here we present new general numerical models on the local stresses induced by arrested dykes. In the models, the crustal segments hosting the dyke vary greatly in mechanical properties, from uniform or non-layered (elastic half-spaces) to highly anisotropic (layers with strong contrast in Young's modulus). The shallow parts of active volcanoes and volcanic zones are normally highly anisotropic and some with open contacts. The numerical results show that, for a given surface deformation, non-layered (half-space) models underestimate the dyke overpressure/thickness needed and overestimate the likely depth to the tip of the dyke. Also, as the mechanical contrast between the layers increases, so does the stress dissipation and associated reduction in surface stresses (and associated fracturing). In the absence of open contacts, the distance between the two dyke-induced tensile and shear stress peaks (and fractures, if any) at the surface is roughly twice the depth to the tip of the dyke. The width of a graben, if it forms, should therefore be roughly twice the depth to the tip of the associated arrested dyke. When applied to the 2009 episode at Harrat Lunayyir, the main results are as follows. The entire 3-7 km wide fracture zone/graben formed during the episode is far too wide to have been generated by induced stresses of a single, arrested dyke. The eastern part of the zone/ graben may have been generated by the inferred, arrested dyke, but the western zone primarily by regional extensional loading. The dyke tip was arrested at only a few hundred metres below the surface, the estimated thickness of the uppermost part of the dyke being between about 6 and 12 m. For the inferred dyke length (strike dimension) of about 14 km, this yields a dyke length/thickness ratio between 2400 and 1200, similar to commonly measured ratios of regional dykes in the field. (C) 2018 Elsevier B.V. All rights reserved.
机译：正确解释火山构造事件期间的表面应力和变形或位移，对于危害评估和堤坝路径预测至关重要。在这里，我们介绍了由堤防引起的局部应力的新通用数值模型。在这些模型中，承载堤坝的地壳段的机械性能差异很大，从均匀或非分层（弹性半空间）到高度各向异性（杨氏模量强烈反差的层）。活火山和火山区的浅层部分通常是高度各向异性的，有些具有敞开的接触面。数值结果表明，对于给定的表面变形，非分层（半空间）模型低估了堤坝所需的超压/厚度，并高估了堤坝尖端的可能深度。而且，随着层之间机械对比度的提高，应力耗散和相关的表面应力降低（以及相关的断裂）也随之增加。在没有开路接触的情况下，两个由堤引起的表面张力和剪切应力峰值（和裂缝，如果有的话）之间的距离大约是堤尖端深度的两倍。因此，a子的宽度（如果形成）应为距相关止动堤顶尖端深度的大约两倍。当应用于Harrat Lunayyir的2009年剧集时，主要结果如下。发作期间形成的整个3-7 km宽的断裂带/地基太宽，以至于无法通过单个停滞的堤坝的诱导应力产生。地带/ grab部的东部可能是由推断的，被捕的堤坝产生的，而西部地带则主要是由区域性延伸载荷产生的。堤顶仅在地表以下几百米处停住，堤最上部的估计厚度在约6至12 m之间。对于推断的堤防长度（走向尺寸）约为14 km，这将导致堤防长度/厚度之比在2400和1200之间，类似于该领域中通常测得的区域堤防之比。 （C）2018 Elsevier B.V.保留所有权利。

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