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，海洋下的板块下沉到大陆之下，进入地球的深部。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断层上，可能会对人类和经济造成毁灭性的影响。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。在这个项目中，梅尔策、贝克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。他们的分析将产生厄瓜多尔地下俯冲带的详细3D图像，2016年厄瓜多尔曾发生7.8级地震。利用机器学习技术，研究人员还将梳理地震仪数据，以寻找小地震的迹象，这些迹象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有助于厄瓜多尔预测和规划潜在的破坏性俯冲带地震。越来越高的分辨率地震研究揭示了俯冲带内和俯冲带之间结构和物理性质的复杂性和多样性。下倾和沿走向的非均质性影响着板块界面上、下倾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，造成重大的人类和经济影响。在2020年10月至2022年11月期间，该小组收集了厄瓜多尔沿海地区由三分量短周期节点和宽带传感器组成的密集阵列记录的陆上-近海主动和被动地震数据。获得这些数据是对法国和德国供资机构支持的HIPER项目(Pedernales地震破裂带高分辨率成像)的补充。这些数据是在2016兆瓦7.8 Pedernales破裂带及其附近收集的，以显著致密HiPer的陆上部分，用于有源记录，并加宽被动记录的孔径，以改善横跨前弧的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，可以检查从地震到非地震的物理性质、结构、流体和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探测能力，旅行时间和环境噪声层析成像和高频接收器的组合作为多步系列反演的输入，以约束地震孕育带沿线和上方以及跨前缘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 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.