SUMMARY

Event screening is an explosion monitoring practice that aims to identify an event as an explosion (‘screened in’) or not (‘screened out’). Confidence in event screening can be increased if multiple independent approaches are used. We describe a new approach to event screening using the seismic moment tensor and its representation on the hypersphere, specifically the 5-sphere of 6-degree unit vectors representing the normalized symmetric moment tensor. The sample of moment tensors from an explosion data set is unimodal on the 5-sphere and can be parametrized by the Langevin distribution, which is sometimes referred to as the Normal distribution on the hypersphere. Screening is then accomplished by finding the angle from the explosion population mean to any newly measured moment tensor and testing if that angle is in the tail of the Langevin distribution (conservatively quantified as greater than 99.9 per cent of the cumulative density). We apply the screen to a sample of earthquakes from the Western USA and the September 2017 explosion and subsequent collapse at the Pungyye-Ri Test Site in North Korea. All the earthquakes and the collapse screen out, but the explosion does not.

中文翻译：

---

地震矩张量事件筛选

概要

事件筛查是一种爆炸​​监视实践，旨在将事件标识为爆炸（“筛入”）或非爆炸（“筛出”）。如果使用多种独立方法，则可以提高事件筛选的信心。我们描述了一种使用地震矩张量及其在超球面上的表示进行事件筛选的新方法，特别是表示标准化对称矩张量的6度单位矢量的5球。来自爆炸数据集的矩张量样本在5球面上是单峰的，并且可以通过Langevin分布（有时称为超球面的正态分布）进行参数化。然后通过找到从爆炸总体平均值到任何新测量的矩张量的角度并测试该角度是否在Langevin分布的尾部（保守地量化为累积密度的99.9％以上）来完成筛选。我们将屏幕应用于来自美国西部的地震以及2017年9月爆炸以及随后在朝鲜的丰吉里（Pungyye-Ri）试验场倒塌的样本。所有的地震和坍塌都被屏蔽掉了，但是爆炸却没有。