Collaborative Research: HIPER - 3D Onshore-Offshore Imaging of Controls on Subduction Zone Megathrust Rupture and Slip Behavior

世界上最大的地震发生在与海洋盆地相关的构造板块下降到地球内部的俯冲带。这些地震发生在将下沉的海洋板块与上覆的大陆板块分开的大断层上。这些地震引起的地面震动对人类和经济造成了重大影响。海底断裂的俯冲带地震会引发海啸，造成额外的破坏。世界上受到这些地震威胁的地区包括美国太平洋西北部和阿拉斯加、中美洲和南美洲、日本和东南亚。在这里，研究人员部署了密集的地震仪阵列，以高分辨率对2016年厄瓜多尔北部近海大地震中破裂的俯冲带的一部分进行成像。该项目利用欧洲资助机构支持的海上和陆上部署的数据采集。对数据的分析提供了一个机会，将沿俯冲带的结构和地震特性的变化与导致大地震的滑动行为的分布联系起来。本研究结果改进了俯冲带附近地震危险性评估。该项目还为一名地震学研究生和本科生的培训提供支持。对俯冲带的高分辨率研究揭示了其构造和物性的复杂性和多样性。下倾和沿向的非均质性影响了板块界面以及上下板块的板块耦合和滑动行为，最终导致大震级地震的发生。Pedernales地震断裂带高分辨率成像（HIPER）项目由法国和德国资助机构资助。它在2016年Mw 7.8 Pedernales断裂附近沿厄瓜多尔北部俯冲带获取主动和被动的海上陆上地震数据。HIPER项目包括60个海底地震仪和150个地面站，这些地面站从三维网格中记录主动震源，然后被动记录地震。在这里，美国团队通过部署密集的3组件短周期节点阵列（约300个）和60个宽带传感器完成了该项目。目标是显著增加HIPER陆上部分的密度，以便进行有源记录。它还扩大了被动记录的孔径，以改善横向覆盖和深度成像。该组合阵列为多尺度三维成像提供了一个绝佳的机会，可以检查结构、流体和地震到地震滑动行为变化之间的关系。最终，它可以将大地测量学和地震学的观测结果与地质、结构和地震活动相协调。数据分析采用机器学习广义相位检测，显著提高源检测。它还包括旅行时间和环境噪声层析成像的组合，以及高频接收器功能作为多步骤一系列反演的输入，以限制地震位置和地震构造沿地震带及其上方。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The largest earthquakes worldwide occur in subduction zones where the tectonic plates associated with ocean basins descend into Earth’s interior. These earthquakes occur on large faults that separate the descending oceanic plate from the overlying continental plate. Ground shaking from these earthquakes have significant human and economic impacts. Subduction zone earthquakes that rupture the seafloor can generate tsunamis that cause additional destruction. Regions of the world at risk from these earthquakes include the U.S. Pacific Northwest and Alaska, Central and South America, Japan, and Southeast Asia. Here, the researchers deploy a dense array of seismometers to image at high resolution a portion of the subduction zone that ruptured offshore northern Ecuador in a large earthquake in 2016. The project leverages data acquisition from an offshore and onshore deployment supported by European funding agencies. Analysis of the data provides an opportunity to link variations in structure and seismic properties along the subduction zone to the distribution of slip behaviors that culminates in large earthquakes. Results from this research improve seismic hazard assessment near subduction zones. The project also provides support for a graduate student in seismology and training of undergraduate students.High resolution studies of subduction zones reveal their complexity and diversity of structure and physical properties. Heterogeneity downdip and along strike influences plate coupling and slip behavior on the plate interface, as well as in the downgoing plate and in the upper plate, which ultimately culminates in large magnitude earthquakes. The HIPER project (High Resolution Imaging of the Pedernales Earthquake Rupture Zone) is supported by French and German funding agencies. It acquires active and passive offshore-onshore seismic data along the northern Ecuador subduction zone in and adjacent to the 2016 Mw 7.8 Pedernales rupture. The HIPER project includes 60 ocean-bottom seismometers and 150 land stations that record active source shots from a 3D grid, followed by passive recording of earthquakes. Here, the U.S. team complete the project by deploying a dense array of 3-component short period nodes (~300) and 60 broadband sensors. The goal is to significantly densify the onshore portion of HIPER for active source recording. It also widens the aperture of passive recording to improve lateral coverage and imaging at depth. The combined arrays present an exceptional opportunity for multiscale 3D imaging and examine the relationship between structure, fluids, and variations in slip behavior from seismic to aseismic. Ultimately, it allows to reconcile observations from geodesy and seismology with geology, structure, and seismicity. Data analysis employs machine learning generalized phase detection to significantly increase source detection. It also involves a combination of traveltime and ambient noise tomography, and high frequency receiver functions as input to a multi-step series of inversions to constrain earthquake locations and seismic structure along and above the seismogenic zone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.