NNSFGEO-NERC: Collaboration: The Role OF Asperities and Slow Slip in Subduction Zone Rupture and Aftershock Sequences: Insights from the 16 April 2016 Pedernales Ecuador Earthquake

在俯冲带中将大洋板块与大陆板块分开的大断层会产生最大的地震和巨大的海啸。例子包括1960年智利、1964年阿拉斯加、2004年印度尼西亚和2011年日本发生的9.0级以上地震。这些大地震对经济和社会产生了重大影响，造成生命和生计损失，建筑物和基础设施受损，商业中断，社区发生变化，可能需要数年时间才能恢复。现代仪器为科学家提供了以新的方式研究这些断层及其产生的地震的机会。2016年4月，足目地震导致厄瓜多尔海岸沿着的俯冲带破裂，发生了一场规模为7.8级的大地震。一项国际快速反应工作部署了一个地震台阵，记录这次大地震后的余震，扩大了厄瓜多尔国家地震和大地测量网络的长期观测。这些数据的分析提供了一个机会，链接结构和地震特性的变化沿着俯冲带的分布观察到的滑动行为之前，期间和之后的地震。这项研究的更广泛影响有可能通过改进俯冲带地震的灾害评估和减灾战略造福社会。在全球许多俯冲带中观察到一系列断层滑动行为（地震、非火山震颤、慢滑动事件、低频地震和极低频地震）。虽然已经形成了一个总体框架，描述了沿板块界面沿着倾斜方向滑动行为的变化，但地震特性与滑动行为之间的直接联系以及慢滑动事件与大逆冲断层地震之间的关系尚未建立。2016年4月，足目地震在一次大型Mw7.8巨型逆冲事件中沿厄瓜多尔海岸沿着俯冲带断裂了约130公里长，100公里宽的一段。地震发生后，立即开展了协调一致的国际快速反应工作，在破裂带和邻近断层段上方部署了一个地震阵列（在陆地和海上使用海底地震仪），这些断层段在十年时间尺度上发生大地震，并观察到缓慢滑动事件。密集的陆上台阵与海上OBS仪器相结合，为研究地震和余震序列提供了一个特殊的数据集。地震阵列得到了快速反应大地测量工作和厄瓜多尔常设国家地震和大地测量网络长期观测的补充。研究人员将利用厄瓜多尔下方纳斯卡板块的俯冲和足目地震和余震序列，将结构和地震特性的沿着走向变化与观察到的滑动行为分布（地震前、地震时和地震后）联系起来，以确定缓慢滑动和巨型逆冲断层破裂之间的关系。综合分析，从各种宽带地震技术将被用来检查凹凸不平的持久性，为大到大地震在多个地震周期，凹凸不平的作用，促进或抑制破裂传播，和锁定和蠕变部分的俯冲界面之间的关系。这项研究的更广泛影响将有助于改进俯冲带地震的风险评估。此外，我们还与非营利非政府组织Build Change合作，开发材料，教育当地社区了解地震危害和建筑技术，以提高复原力。该项目支持地震学和计算的学术研究基础设施，以及早期职业科学家的专业发展和培训。 这项研究的结果将被纳入研究生和本科生的STEM教育中。该项目由国际科学与工程办公室共同资助。

The large faults that separate oceanic plates from continental plates in subduction zones generate the largest earthquakes and giant tsunami. Examples include earthquakes with magnitude 9.0 and larger in Chile in 1960, Alaska in 1964, Indonesia in 2004, and Japan in 2011. These giant earthquakes have significant economic and social impact causing loss of life and livelihoods, damage to buildings and infrastructure, disruption of business, and changes in communities that can take years for recovery. Modern instrumentation provides scientists the opportunity to study these faults and the earthquakes they generate in new ways. In April 2016, the Pedernales Earthquake ruptured the subduction zone along the coast of Ecuador in a large Mw 7.8 earthquake. An international rapid response effort deployed a seismic array to record aftershocks following this large earthquake that expanded long term observations of the national seismic and geodetic network in Ecuador. Analysis of these data provide an opportunity to link variations in structure and seismic properties along the subduction zone to the distribution of slip behaviors observed before, during, and after the earthquake. The broader impacts of this research have the potential to benefit society through improved hazard assessment and mitigation strategies for subduction zone earthquakes.A spectrum of fault slip behaviors (earthquakes, non-volcanic tremor, slow slip events, low-frequency earthquakes and very low-frequency earthquakes has been observed in a number of subduction zones globally. While a general framework has developed characterizing the variation in slip behaviors in the dip direction along the plate interface, a direct link between seismic properties and slip behavior and the relationship between slow-slip events and megathrust earthquakes has yet to be established. In April 2016, the Pedernales Earthquake ruptured an approximately 130 km long, 100 km wide segment of the subduction zone along the coast of Ecuador in a large Mw 7.8 megathrust event. Immediately after the earthquake a coordinated international rapid response effort deployed a seismic array (on land and offshore using ocean bottom seismometers, OBS) above the rupture zone and adjacent fault segments where large earthquakes occur on decadal time scales and slow slip events have been observed. The dense on land array combined with offshore OBS instruments provides an exceptional dataset to study the earthquake and aftershock sequence. The seismic array is complemented by rapid response geodetic efforts and long term observations from permanent national seismic and geodetic networks in Ecuador. The researchers will use subduction of the Nazca Plate beneath Ecuador and the Pedernales Earthquake and aftershock sequence to link along strike variations in structure and seismic properties to the distribution of slip behaviors observed (pre-, co- and post-seismic) to determine the relationship between slow slip and megathrust rupture. The integrated analyses from a variety of broadband seismic techniques will be used to examine the persistence of asperities for large to great earthquakes over multiple seismic cycles, the role of asperities in promoting or inhibiting rupture propagation, and the relationship between locked and creeping parts of the subduction interface. Broader impacts of this research will contribute to improved risk assessment from subduction zone earthquakes. In addition we are partnering with Build Change, a non-profit NGO, to develop materials to educate local communities on earthquake hazards and construction techniques to improve resiliency. This project supports academic research infrastructure in seismology and computation, and professional development and training for early career scientists. Results from this research will be integrated into STEM education at both the graduate and undergraduate level.This project is cofunded by the Office of International Science and Engineering.