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俯冲带，在那里，与海洋盆地相关的构造板块下沉到地球内部。这些地震发生在将下降的大洋板块与上覆的大陆板块分开的大断层上。这些地震造成的地面震动对人类和经济都有重大影响。俯冲带地震使海底破裂，可能会产生海啸，造成额外的破坏。世界上面临这些地震风险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，以高分辨率对俯冲带的一部分进行成像。2016年，厄瓜多尔北部近海发生大地震，俯冲带破裂。该项目利用从欧洲资助机构支持的离岸和陆上部署获得的数据。对数据的分析提供了一个机会，将俯冲带上的结构和地震性质的变化与最终导致大地震的滑动行为的分布联系起来。这项研究的结果改善了俯冲带附近的地震危险性评估。该项目还为地震学研究生和本科生培训提供支持。对俯冲带的高分辨率研究揭示了它们结构和物理性质的复杂性和多样性。非均质下倾和沿走向影响板块界面、下沉板块和上板块的板块耦合和滑动行为，最终导致大震级地震。HIPER项目(Pedernales地震破裂带的高分辨率成像)得到了法国和德国资助机构的支持。它获得了厄瓜多尔北部俯冲带的主动和被动近海-陆上地震数据，这些数据位于2016兆瓦7.8 Pedernales断裂内及其附近。HiPer项目包括60个海底地震仪和150个陆地站，它们从3D网格记录主动震源快照，然后被动记录地震。在这里，美国团队通过部署密集的三分量短周期节点阵列(约300个)和60个宽带传感器来完成该项目。其目标是使HiPer的陆上部分显著致密，以用于有源记录。它还扩大了被动记录的孔径，以改善横向覆盖和深度成像。组合的阵列为多尺度3D成像提供了一个特殊的机会，并检查了结构、流体和从地震到非地震的滑动行为变化之间的关系。最终，它可以使大地测量学和地震学的观测结果与地质、构造和地震活动相一致。数据分析使用机器学习广义相位检测来显著提高源检测。它还涉及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一系列多步反演的输入，以约束地震孕育区沿线和上方的地震位置和地震结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.