Collaborative Research: Deep megathrust conditions by comparing seismicity rates and source parameters with tremor, slow slip, and the Mw 7.4 Ometepec, Mexico earthquake

最近的发现表明，沿俯冲大逆冲断层的断层滑动范围很广，这引发了关于大地震、小地震、慢滑动和非火山地震之间关系的重要问题。在许多地区，断层的深层部分位于快滑和慢滑机制之间的过渡处，位于近海，远离附近的监测。然而，沿中美洲俯冲带瓦哈坎段现有的地震和大地测量网提供了一个很好的数据集，用于量化经历过7级地震、震颤和慢滑事件的地区的地震发生和震源参数。本研究将探讨与慢滑、震颤和大地震之间的时空关系有关的几个假设。这些包括确定1)当地震活动接近下倾地震活动极限和偶发性震颤和滑动区域时，沿大逆冲断层是否存在地震活动特征的急剧转变；2)慢滑动事件是否在邻近区域产生应力加载，从而导致地震活动率增加和小地震震源特征的变化。③大地震是否与邻近区域因应力变化引起的地震发生和震源特征的时间变化有关。我们将采用几种地震学技术，包括建立统一的事件目录，确定震源机制，计算破裂持续时间和应力降，以及沿着特定断层斑块调查地震活动率，以解决这些假设。该项目的总体目标围绕着更好地了解墨西哥俯冲带地震产生区域的深层根源，并适用于其他全球俯冲带。因此，这项研究的结果将产生与地震灾害有关的社会效益，特别是在提供改善概率地震灾害的时间变化所需的信息方面。该项目的成果将包括通过会议介绍、出版物和有关数据存储库的档案向广泛的国际社会传播数据产品。该项目将培训4名在美国的研究生和本科生，并为2名墨西哥学生提供地震能力建设培训。该项目的另一个成果是2个教育课程，将通过在线教育活动门户网站传播。

Recent discoveries that demonstrate the wide spectrum of fault slip along subduction megathrust faults prompt important questions about the relationships between large earthquakes, small earthquakes, slow slip, and non-volcanic tremor. In many areas, the deep portion of the fault that lies at the transition between the fast and slower slip mechanisms is out of view, sitting offshore, away from nearby monitoring. However, an existing seismic and geodetic network along the Oaxacan segment of the Middle America subduction zone provides an excellent dataset for use to quantify earthquake occurrence and source parameters in an area that has experienced M 7 earthquakes, tremor, and slow slip events. This research will address several hypotheses related to the spatial and temporal relationships between slow slip, tremor, and large earthquakes. These include determining 1) if a sharp transition in seismicity characteristics exists along the megathrust as events approach the downdip seismicity limit and the area of episodic tremor and slip, 2) if slow slip events produce stress loading in adjacent regions that lead to increased seismicity rates and changes in source characteristics of small earthquakes, and 3) if large earthquakes are associated with temporal changes in earthquake occurrence and source characteristics in adjacent regions due to stress changes. We will employ several seismological techniques, including the construction of a uniform event catalog, focal mechanism determination, rupture duration and stress drop calculations, and investigation of seismicity rates along specific fault patches, to address these hypotheses.The overall goals of the project revolve around a better understanding of the deep roots of the earthquake-producing region of the Mexican subduction zone, with applicability to other global subduction zones. Thus the results of the study will produce societal benefits related to earthquake hazards, particularly in providing information needed for improving temporal variations in probabilistic seismic hazard. The outcome of this project will include data products disseminated to a wide international community through meeting presentations, publications, and archival in the relevant data repositories. The project will train 4 US based graduate and undergraduate students as well as provide capacity-building seismological training for 2 Mexican students. Another outcome of the project will be 2 educational lessons that will be disseminated through online educational activity portals.