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

在俯冲带将大洋板块和大陆板块分开的大断层会产生最大的地震和巨大的海啸。1960年的智利地震、1964年的阿拉斯加地震、2004年的印度尼西亚地震和2011年的日本地震都是9.0级以上的地震。这些大地震具有重大的经济和社会影响，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引发的地震的机会。2016年4月，佩德纳莱斯地震（Pedernales Earthquake）引发7.8级大地震，破坏了厄瓜多尔沿海的俯冲带。在这次大地震之后，国际快速反应行动部署了一个地震阵列来记录余震，扩大了厄瓜多尔国家地震和大地测量网的长期观测。对这些数据的分析提供了将沿俯冲带的结构和地震性质变化与地震前、地震中和地震后观察到的滑动行为分布联系起来的机会。这项研究的更广泛影响有可能通过改进对俯冲带地震的危害评估和减灾战略而造福社会。在全球许多俯冲带中观测到一系列断层滑动行为（地震、非火山地震、慢滑事件、低频地震和极低频地震）。虽然沿板块界面倾斜方向滑动行为变化的一般框架已经形成，但地震性质与滑动行为之间的直接联系以及慢滑事件与大逆冲地震之间的关系尚未建立。2016年4月，Pedernales地震在厄瓜多尔海岸发生了一次7.8兆瓦的大型逆冲断层，导致约130公里长、100公里宽的俯冲带断裂。地震发生后，国际快速反应协调工作立即在断裂带和邻近断层段上方部署了地震阵列（在陆地和海上使用海底地震仪，OBS），这些断裂带和相邻断层段每十年发生一次大地震，并观察到缓慢滑动事件。密集的陆地阵列与海上OBS仪器相结合，为研究地震和余震序列提供了独特的数据集。厄瓜多尔永久国家地震和大地测量网的快速反应大地测量工作和长期观测补充了地震阵列。研究人员将利用厄瓜多尔纳斯卡板块的俯冲作用和Pedernales地震和余震序列，将沿走向的结构变化和地震特性与观察到的滑动行为分布（地震前、地震中和地震后）联系起来，以确定慢滑动和大逆冲断裂之间的关系。各种宽带地震技术的综合分析将用于检查多个地震周期中大地震到大地震的凸起的持久性，凸起在促进或抑制破裂传播方面的作用，以及俯冲界面的锁定部分和蠕动部分之间的关系。本研究的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，向当地社区宣传地震危害和提高抗灾能力的建筑技术。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整合到研究生和本科生的STEM教育中。本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.