Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines
Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines
复制标题
自动地震处理管道中余震分类的迭代策略
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
D. Dodge
中科院分区：
文献类型：
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作者：
S. Gibbons;T. Kværna;D. Harris;D. Dodge
大地震后的余震序列对近真实的时间生成地震公告提出了巨大的挑战。重新定位膨胀的事件数量所需的分析人员资源增加，加上相位关联算法的失败和基础的全自动事件公告质量的显著恶化。当前的处理管道是在一代人之前设计的，并且由于当时的计算限制，通常仅限于原始数据的单次传递。利用当前的处理能力，多次通过数据是可行的。在每个站点处理原始数据目前会生成参数数据流，然后通过相位关联算法扫描这些数据流以形成事件假设。我们考虑的情况下，一个大地震已经发生，并建议定义一个区域的可能余震活动中的事件被检测到，并准确定位，使用一个单独的专门针对半自动的过程。这项工作可能集中在所谓的模式检测器上，但在这里，我们展示了一种更通用的网格搜索算法，它可以覆盖更广泛的源区域，而不需要波形相似性。考虑到我们的震源区域内有许多位置良好的余震，我们可以在相位关联算法的新迭代之前从原始检测列表中删除所有相关的相位。我们为2015年尼泊尔Gorkha序列提供了一个概念验证的例子，该序列记录在国际监测系统的地震阵列上。即使在非常保守的条件下定义余震震源区内的事件假设，我们也可以自动删除大约一半的可能由尼泊尔地震产生的原始检测，并减少错误关联和虚假事件假设的可能性。使用相关和子空间检测器和/或经验匹配场处理，可能进一步减少参数数据流中的检测次数。
Aftershock sequences following very large earthquakes present enormous challenges to near‐real‐time generation of seismic bulletins. The increase in analyst resources needed to relocate an inflated number of events is compounded by failures of phase‐association algorithms and a significant deterioration in the quality of underlying, fully automatic event bulletins. Current processing pipelines were designed a generation ago, and, due to computational limitations of the time, are usually limited to single passes over the raw data. With current processing capability, multiple passes over the data are feasible. Processing the raw data at each station currently generates parametric data streams that are then scanned by a phase‐association algorithm to form event hypotheses. We consider the scenario in which a large earthquake has occurred and propose to define a region of likely aftershock activity in which events are detected and accurately located, using a separate specially targeted semiautomatic process. This effort may focus on so‐called pattern detectors, but here we demonstrate a more general grid‐search algorithm that may cover wider source regions without requiring waveform similarity. Given many well‐located aftershocks within our source region, we may remove all associated phases from the original detection lists prior to a new iteration of the phase‐association algorithm. We provide a proof‐of‐concept example for the 2015 Gorkha sequence, Nepal, recorded on seismic arrays of the International Monitoring System. Even with very conservative conditions for defining event hypotheses within the aftershock source region, we can automatically remove about half of the original detections that could have been generated by Nepal earthquakes and reduce the likelihood of false associations and spurious event hypotheses. Further reductions in the number of detections in the parametric data streams are likely, using correlation and subspace detectors and/or empirical matched field processing.