Collaborative Research: 3D 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”，在那里海洋板块下降到大陆之下，进入地球的深处。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断层上，可能对人类和经济造成毁灭性的影响。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。在这个项目中，Meltzer、Beck和他们的团队将与欧洲科学家合作，分析他们在2020年至2022年期间部署在厄瓜多尔北部的地震仪记录的数据。他们的分析将得出2016年发生7.8级地震的厄瓜多尔地下俯冲带的详细3D图像。利用机器学习技术，研究人员还将梳理地震仪数据，寻找小地震的迹象，这些小地震的位置可以勾勒出主要俯冲带断层和其他局部断层的几何形状。研究小组将利用图像和地震数据来推断主要俯冲带断层的哪些部分可能引发大地震。研究小组和厄瓜多尔同事的这些发现和相关活动将帮助厄瓜多尔预测和计划潜在的破坏性俯冲带地震。越来越高分辨率的地震研究揭示了俯冲带内部和之间构造和物理性质的复杂性和多样性。下倾和沿向非均质性影响板块界面、下行板块和上行板块的板块耦合和滑动行为，最终导致大震级地震，对人类和经济造成重大影响。在2020年10月至2022年11月期间，该团队收集了厄瓜多尔沿海地区由3分量短周期节点和宽带传感器密集阵列记录的陆上和海上主动和被动地震数据。这些数据是作为法国和德国资助机构支持的Pedernales地震断裂带高分辨率成像（HIPER）项目的补充而获得的。这些数据是在2016年Mw 7.8 Pedernales破裂带及其附近收集的，以显著增强HIPER的陆上部分，用于主动源记录，并扩大被动记录的孔径，以提高整个前弧深度的横向覆盖和成像。该组合阵列为多尺度三维成像提供了一个绝佳的机会，可以检查物理性质、结构、流体以及地震到地震滑动行为变化之间的关系。对这些数据的分析将使用机器学习来显著提高震源检测，并将旅行时间和环境噪声层析成像以及高频接收器函数相结合，作为多步系列反演的输入，以限制地震位置和地震构造沿著发震区及其上方和穿过弧前。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 plates under the oceans descend beneath continents and into Earth’s deep interior. These earthquakes, which occur on faults that separate the descending oceanic plate from the overlying continental plate, can have devastating human and economic impacts. 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. In this project, Meltzer, Beck, and their team will analyze data recorded by seismometers that they deployed in northern Ecuador between 2020 and 2022, in coordination with European scientists. Their analyses will result in detailed 3D images of the subduction zone beneath Ecuador, where a magnitude 7.8 earthquake occurred in 2016. Using machine learning techniques, the researchers will also comb the seismometer data for signs of small earthquakes, whose locations can outline the geometry of the main subduction zone fault and other local faults. The research team will use the images and earthquake data to infer which parts of the main subduction zone fault could give rise to large earthquakes. These findings and related activities by the research team and Ecuadoran colleagues will help Ecuador anticipate and plan for potentially devastating subduction zone earthquakes.Increasingly high resolution seismic studies reveal the complexity and diversity of structure and physical properties within and between subduction zones. Downdip and along-strike heterogeneity influences plate coupling and slip behavior on the plate interface, in the downgoing plate, and in the upper plate, ultimately culminating in large magnitude earthquakes with significant human and economic impacts. Between October 2020 and November 2022, the team collected onshore-offshore active and passive seismic data recorded by a dense array of 3-component short period nodes and broadband sensors in coastal Ecuador. These data were acquired as a complement to the HIPER project (High Resolution Imaging of the Pedernales Earthquake Rupture Zone) supported by French and German funding agencies. The data were collected in and adjacent to the 2016 Mw 7.8 Pedernales rupture zone to significantly densify the onshore portion of HIPER for active-source recording, and to widen the aperture of passive recording to improve lateral coverage and imaging at depth across the forearc. The combined arrays present an exceptional opportunity for multiscale 3D imaging to examine the relationship between physical properties, structure, fluids, and variations in slip behavior from seismic to aseismic. Analysis of these data will employ machine learning to significantly increase source detection, and 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 and across the forearc.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.