Developing Methods for Detection and Analysis of Repeating Earthquakes and Low Frequency Earthquakes Using Cascadia Initiative Amphibious Network Data

太平洋西北部受到与卡斯卡迪亚俯冲带有关的地震和海啸危险，这是由于分隔北美板块和下行太平洋板块的板块边界断层上的反复滑动。滑动沿断层在时间和空间上有所不同，了解滑动模式可以带来新的见解，即哪些断层段最有可能产生破坏性的“巨型逆冲”事件(大于8级)。通过研究整个地震周期中发生的较小事件(加载、破裂、震后、重新加载等)，这项研究可以为更新的区域风险评估提供背景。一名本科生实习生和一名博士生将接受使用陆上和海上数据的地震学培训。卡斯卡迪亚巨型逆冲断层的一部分滑动行为谱将利用两栖阵列重新占用的地球望远镜可移动阵列站点和OBSIP海底地震仪的地震数据进行研究。卡斯卡迪亚倡议(CI)持续4年的小规模重复地震将被记录下来，它们的分布将根据断层特征和俯冲板块内结构可能的沿走向变化来解释。海上覆盖预计将消除目前观测中的偏差，在这些观测中，只有陆上结果表明低频事件(LFE)只发生在孕震带的下倾部分。一项初步研究证实，计划中的自动光谱检测方法可以在CI海底地震仪数据上取得成功。在巨型逆冲带的上倾部分有可能发生浅层重复事件，沿着卡斯卡迪亚俯冲带，可能存在源区特征的水平和类型的变化，可能包括新的LFE。为本科课程设计的课程将在IRIS InClass和SERC服务器上开发和存档。事件目录和震源参数结果将通过出版物增刊和至少一个NSF支持的开放数据库(IEDA)提供。

The Pacific Northwest is subject to earthquake and tsunami hazard associated with the Cascadia subduction zone, due to recurring slip on the plate boundary fault that separates the North America plate and the downgoing Pacific plate. Slip varies in time and space along the fault and understanding the slip patterns can lead to new insights about which fault sections are most likely to produce damaging 'megathrust' events (greater than magnitude 8). By studying smaller events that occur throughout a seismic cycle (loading, rupture, post seismic, reloading etc) this study can provide context for updated regional hazard assessment. An undergraduate intern and a PhD student will receive seismology training using both onshore and offshore data. A portion of the spectrum of slip behaviors along the Cascadia megathrust fault will be studied using seismic data from the Amphibious Array- reoccupied EarthScope Transportable Array sites and OBSIP ocean bottom seismometers. Small repeating earthquakes will be documented for the 4-yr duration of Cascadia Initiative (CI) and their distribution will be interpreted in terms of fault character and possible along-strike variation in structure within the subducting plate. The offshore coverage is expected to eliminate a current bias in observations where onshore-only results suggest that low frequency events (LFE) only occur in the down-dip part of the seismogenic zone. A pilot study confirms that the planned automated spectral detection method can succeed on CI ocean bottom seismometer data. There is potential for shallow repeating events to occur in the up-dip portion of the megathrust zone and there may be variations in level and type of source signature, including possibly new LFE, along the Cascadia subduction zone. A lesson designed for an undergraduate course will be developed and archived on the IRIS InClass and SERC servers. The event catalog and source parameter results will be made available via publication supplements and at least one NSF-supported open database (IEDA).