Intrinsic versus extrinsic variability of analogue sand-box experiments – Insights from statistical analysis of repeated accretionary sand wedge experiments
Intrinsic versus extrinsic variability of analogue sand-box experiments – Insights from statistical analysis of repeated accretionary sand wedge experiments
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DOI：
10.1016/j.jsg.2015.03.008
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发表时间：
2015-06
影响因子：
3.1
通讯作者：
T. Santimano;M. Rosenau;O. Oncken
中科院分区：
文献类型：
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作者：
T. Santimano;M. Rosenau;O. Oncken
即使在控制的边界条件下，模拟模型也不是完全可复制的，这使得它们的解释和应用并不总是直截了当的。正如任何科学实验一样，它们包括一些随机成分，这些成分可能受到内在（固有过程）和外在（边界条件，材料特性）来源的影响。为了帮助评估模拟模型结果，我们区分和量化了在受控环境中重复的“沙盒”增生楔模型结果的内在和外在变异性。可变性的外在来源，即参数的变化是介质的性质（材料、摩擦和厚度）。实验观测结果包括断层的几何特性（寿命、间距、倾角）以及楔形几何特性（高度、坡度、长度）。对于每个变量，我们计算方差系数（CV），并使用卡方检验（χ2）将变异性量化为对称分布（正态分布，拉普拉斯分布）或不对称分布（Gamma）。断层倾角/逆冲倾角（CV = 0.6-0.7/0.2-0.6）等观测值变化较小，且随基底摩擦力的减小而减小。与时间相关的变量，如断层寿命（CV = 0.19-0.56）和断层间距（CV = 0.12 - 0.36）具有更高的CV，从而影响楔形斜率的变异性（CV = 0.12 - 0.33）。这些观测值也随着基础摩擦的增加而增加。随着时间的推移，楔形的机械复杂性增加，CV和分布的不对称性也会增加。此外，我们用方差分析验证了实验的重复性。通过对重复实验结果的统计分析，我们提出了一种量化变异性的工具，以及一种更好地了解模拟砂楔变形动态力学的替代方法。
Analogue models are not perfectly reproducible even under controlled boundary conditions which make their interpretation and application not always straight forward. As any scientific experiment they include some random component which can be influenced both by intrinsic (inherent processes) and extrinsic (boundary conditions, material properties) sources. In order to help in the assessment of analogue model results, we discriminate and quantify the intrinsic versus extrinsic variability of results from “sandbox” models of accretionary wedges that were repeated in a controlled environment. The extrinsic source of variability, i.e. the parameter varied is the nature of the décollement (material, friction and thickness). Experiment observables include geometric properties of the faults (lifetime, spacing, dip) as well as wedge geometry (height, slope, length).For each variable we calculated the coefficient of variance (CV) and quantified the variability as a symmetric distribution (Normal, Laplacian) or asymmetric distribution (Gamma) using a Chi squared test (χ2). Observables like fault dip/back thrust dip (CV = 0.6–0.7/0.2–0.6) are less variable and decrease in magnitude with decreasing basal friction. Variables that are time dependent like fault lifetime (CV = 0.19–0.56) and fault spacing (CV = 0.12 – 0.36) have a higher CV consequently affecting the variability of wedge slope (CV = 0.12–0.33). These observables also increase in magnitude with increasing basal friction. As the mechanical complexity of the evolving wedge increases over time so does the CV and asymmetry of the distribution. In addition, we confirm the repeatability of experiments using an ANOVA test. Through the statistical analysis of results from repeated experiments we present a tool to quantify variability and an alternative method to gaining better insights into the dynamic mechanics of deformation in analogue sand wedges.