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相关的地震和海啸灾害的影响，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的反复滑动。滑动在时间和空间上沿着断层变化，了解滑动模式可以导致关于哪些断层部分最有可能产生破坏性的“巨型逆冲断层”事件（大于8级）的新见解。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灾害评估提供背景。一名本科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。将利用两栖台阵-重新占用的EarthScope移动台阵场地和OBSIP海底地震仪的地震数据，对沿沿着卡斯卡迪亚巨型逆冲断层的滑动行为的部分频谱进行研究。小重复地震将被记录为4年的卡斯卡迪亚倡议（CI）的持续时间和他们的分布将被解释的断层特征和可能的沿走向的变化在俯冲板块内的结构。海上覆盖预计将消除目前的观测偏差，只有在岸上的结果表明，低频事件（LFE）只发生在下倾部分的孕震区。初步研究证实，计划的自动频谱检测方法可以成功的CI海底地震仪数据。在巨型逆冲带的上倾部分可能发生浅层重复事件，震源特征的水平和类型可能会发生变化，包括沿着卡斯卡迪亚俯冲带可能出现新的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。事件目录和源参数结果将通过出版物补充和至少一个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).