Bias Corrected Estimation of Paleointensity (BiCEP): An Improved Methodology for Obtaining Paleointensity Estimates
Bias Corrected Estimation of Paleointensity (BiCEP): An Improved Methodology for Obtaining Paleointensity Estimates
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DOI：
10.1029/2021gc009755
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发表时间：
2021-08-01
影响因子：
3.5
通讯作者：
Tauxe, Lisa
中科院分区：
文献类型：
--
作者：
Cych, Brendan;Morzfeld, Matthias;Tauxe, Lisa
在许多自然和考古资料中违反了古强度实验的假设，导致Arai样地不呈线性，产生的古强度估计不准确，导致结果存在偏差。最近，古地磁学家采用了一套“选择标准”，将具有非线性Arai图的标本排除在分析之外，但在古地磁学界对使用哪一套标准几乎没有共识。在这项研究中，我们提出了一种统计方法，我们称之为偏差校正估计古强度（BiCEP），它假设每个标本记录的古强度偏离真实答案的程度取决于Arai图上的非线性（曲率参数(k)右箭头）的单个度量。我们可以使用这种经验关系来估计样本的记录古强度，其中(k)超过右箭头=0，即一条完美的直线。我们将BiCEP方法应用于30个站点的集合，其中原始字段的真实值受到很好的约束。我们的方法返回准确的古强度估计值，具有与限制性古强度标准集相似的准确度和精度水平，但接受的地点与允许的标准一样多。与使用这些选择标准相比，BiCEP方法具有显著的优势，因为它在不排除大量标本的情况下获得了这些准确的结果。尽管不精确，但它从所有标本都不符合传统标准的地点得出了准确的估计。BiCEP结合了最严格的选择标准的准确性和较不可靠的“松散”标准的低故障率。古地磁学家在岩石和陶器碎片（以及其他东西）上进行实验，以估计古代地球磁场随时间的强度（古强度）。这些假设经常被违背，从而导致偏见。定量度量（选择标准）试图筛选出“坏”数据。如果一个特定的实验不符合标准，结果就会被忽略。然而，对于哪一套标准是最重要的，哪一套标准被认为是失败的，人们缺乏一致意见。其中一个标准量化了古代磁化和实验室磁化之间线性基本假设的偏差。我们提出了一种新的贝叶斯方法，称为偏差校正估计的古强度（BiCEP），其中我们假设估计的古强度依赖于这个偏差。然后，我们可以使用这种依赖关系来纠正在与理想行为有不同偏差的标本集合上产生的古强度。BiCEP使我们能够计算出古代磁场的准确估计，而不会忽略非理想样本的结果。我们在原始磁场强度受限的古磁数据上测试了BiCEP。BiCEP恢复场强的精度与更严格的标准集相似，但得到的结果适用于更多的地点。
The assumptions of paleointensity experiments are violated in many natural and archeological materials, leading to Arai plots which do not appear linear and yield inaccurate paleointensity estimates, leading to bias in the result. Recently, paleomagnetists have adopted sets of "selection criteria" that exclude specimens with nonlinear Arai plots from the analysis, but there is little consensus in the paleomagnetic community on which set to use. In this study, we present a statistical method we call Bias Corrected Estimation of Paleointensity (BiCEP), which assumes that the paleointensity recorded by each specimen is biased away from a true answer by an amount that is dependent a single metric of nonlinearity (the curvature parameter (k) over right arrow) on the Arai plot. We can use this empirical relationship to estimate the recorded paleointensity for a specimen where (k) over right arrow =0, that is, a perfectly straight line. We apply the BiCEP method to a collection of 30 sites for which the true value of the original field is well constrained. Our method returns accurate estimates of paleointensity, with similar levels of accuracy and precision to restrictive sets of paleointensity criteria, but accepting as many sites as permissive criteria. The BiCEP method has a significant advantage over using these selection criteria because it achieves these accurate results without excluding large numbers of specimens from the analysis. It yields accurate, albeit imprecise estimates from sites whose specimens all fail traditional criteria. BiCEP combines the accuracy of the strictest selection criteria with the low failure rates of the less reliable "loose" criteria.Plain Language Summary Paleomagnetists perform experiments on rocks and pottery sherds (among other things) to estimate the strength of the ancient Earth's magnetic field (the paleointensity) through time. These make assumptions that are frequently violated, leading to bias. Quantitative metrics (selection criteria) attempt to screen out "bad" data. If a particular experiment fails the criteria, the results are ignored. However, there is a lack of agreement as to which set of criteria are the most important and what is considered a failure. One of these criteria quantifies the deviation from the fundamental assumption of linearity between the ancient and laboratory magnetizations. We present a new Bayesian method called Bias Corrected Estimation of Paleointensity (BiCEP), in which we assume that the estimated paleointensity depends on this deviation. We can then use this dependency to correct the paleointensity made on an ensemble of specimens with differing deviations from ideal behavior. BiCEP allows us to calculate accurate estimates of the ancient magnetic field, without ignoring results from nonideal specimens. We test BiCEP on paleomagnetic data for which the original field strength is well constrained. BiCEP recovers the field strength with similar accuracy to stricter sets of criteria, but gets results for a greater number of sites.