深度学习驱动的地震目录构建:PhaseNet和EqT模型的对比与评估

Deep-Learning-Empowered Earthquake Catalog Building: Comparison and Evaluation of PhaseNet and EqT Models

  • 摘要: 随着地震台站数目的增加,以纯人工的分析方式拾取震相到时并编制地震目录难以满足地震目录实时自动化构建的要求。随着人工智能技术的发展,涌现出多个用于震相拾取的深度学习模型,为高分辨率地震目录的自动化构建提供了机遇,但这些模型在不同应用场景中的性能和适用性仍不明确。以2019年美国加利福尼亚州Ridgecrest地震序列和2019年中国四川威远Ms 5.4地震序列为例,对当前两种先进的震相拾取深度学习模型PhaseNet和EqT(含EqT1和EqT2两套参数)的性能及其构建的地震目录的完备性和准确性进行了测试和评估。结果表明,尽管PhaseNet和EqT最初是使用来自不同地区的数据集训练的,在跨区域应用时仍然能够取得良好的效果,到时拾取的精度可以达到十几个毫秒,与人工分析相当。EqT1即便采用低检测阈值,也能保持很高的查准率,误报少,所构建地震目录的准确性更好,但查全率有限,检测到的地震数量少于PhaseNet。PhaseNet的拾取效果随阈值选择的不同具有较大的弹性,采用中低阈值时具有较高的查全率,采用高阈值则可以达到与EqT1相当的查准率。与EqT1和PhaseNet相比,EqT2性能较差,不推荐使用。

     

    Abstract:
      Objectives  Manual seismic phase picking and earthquake catalog building become challenging because the number of seismic stations increases. With the rapid development of artificial intelligence, several deep learning models are developed for seismic phase picking, but their performance and applicability remain ambiguous.
      Methods  PhaseNet and EqT can extract relevant features at different levels from raw seismic waveforms and map them into probabilistic sequences. In this paper, the performance of these two widely-used deep learning models for earthquake detection and phase picking is investigated with the 2019 Ridgecrest earthquake (California, USA) sequence and the 2019 Weiyuan Ms 5.4 earthquake (Sichuan, China) sequence. Besides, the completeness and accuracy of the constructed earthquake catalogs are analyzed and evaluated by cross-validation.
      Results  The results show that the two models, though trained with datasets from different regions, perform well in cross-region applications and are comparable to manual analysis. EqT1 provides high detection precision with few false alarms, even under a low threshold. But EqT1 has a limited recall rate, implying that fewer earthquakes are detected compared with PhaseNet. The picking performance of PhaseNet is sensitive to the employed threshold. With the low and moderate thresholds, PhaseNet can detect more earthquakes than EqT1 and manual catalog, while registering a relatively low detection precision. With the high threshold, the precision of PhaseNet is comparable to that of EqT1. EqT2 is not recommended due to its inferior performance over EqT1 and PhaseNet.
      Conclusions  EqT1 provides a higher precision when being employed for seismic phase picking, leading to earthquake catalogs with better accuracy. PhaseNet has a higher recall rate and generates more complete catalogs. Both models can facilitate automatic and rapid construction of earthquake catalogs.

     

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