Investigating Mantle Dynamics in the Pacific Northwest Using 3D Anisotropic Velocity Models from Surface Wave Tomography

使用表面波断层扫描 3D 各向异性速度模型研究太平洋西北地区的地幔动力学

• 批准号: 2224229
• 负责人: Aibing Li
• 金额: $ 16.78万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2224229&HistoricalAwards=false
• 关键词: Investigating; Mantle; Dynamics; Pacific; Northwest

The Pacific Northwest (PNW) is in a unique geological setting, where the oceanic Juan De Fuca (JDF) plate is subducting under the North American plate. It is believed that the JDF slab has interacted with the Yellowstone hotspot since at least 20 million years ago, generating pervasive volcanism in the northwestern United States. The plate subduction and the slab-hotspot interaction are the driving forces for the surface geology in the PNW, including volcanoes and earthquakes. The alignment of age-progressive volcanos (hotspot track) in the Snake River Plain (SRP) is SW-NE, agreeing with the plate motion of the North American plate, suggesting the Yellowstone hotspot is probably a plume that originates from the deep mantle, like the Hawaii hotspot. However, the volcanos in the High Lava Plains (HLP) form a hotspot track in the NW direction, against the plume hypothesis. The mechanisms for the bimodal hotspot tracks and the voluminous magmatism in the PNW are still under debate. Previous seismic velocity models beneath the northwestern United States have improved the understanding of the complex geology in the area. The velocity of a seismic wave also depends on its propagation direction, called seismic anisotropy, which is associated with lithospheric deformation and mantle flow. Therefore, imaging seismic anisotropy is critical to understanding the dynamic mantle process of the earth. The investigator will produce a high-resolution, 3D seismic anisotropy model in the Pacific Northwest to address the slab-hotspot interaction and its contribution to the extensive volcanism. The model is also helpful in understanding and monitoring seismicity and volcano eruptions in the area. The project will train one graduate and one undergraduate student in seismic data processing and tomography methods. The research results will be shared with the scientific community through conferences, journals, and websites and with students in the investigator’s undergraduate and graduate courses at the University of Houston, a minority serving institution. Oceanic plate subduction, back-arc volcanism, and hotspot activity have shaped the geological history of the Pacific Northwest. Many high-resolution seismic models have been developed using data from the USArray Transportable Array (TA), improving our understanding of tectonics and geodynamics in the region. However, whether the source of the widespread magmatism along the SRP and HLP is from a mantle plume or intruding hot oceanic asthenosphere is not resolved. Many local velocity anomalies imply complex small-scale mantle convection in the region, which has not been verified in current anisotropic models with limited lateral or vertical resolution. The investigator will construct a high-resolution anisotropic model using Rayleigh and Love wave data from earthquakes recorded at the TA and other coexisting stations in the northwestern United States. The resolution for radial and azimuthal anisotropy in these models is similar to that for isotropic velocity, helping reveal detailed mantle dynamic processes and test possible mechanisms for geophysical observations in the Pacific Northwest.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.

西北太平洋（PNW）处于独特的地质环境中，海洋胡安·德福卡（Juan de Fuca）（JDF）板在北美板块下方俯冲。据信，JDF平板至少在2000万年前就与黄石热点互动，在美国西北部产生了普遍的火山。板俯冲和平板柱相互作用是PNW中表面地质的驱动力，包括火山和地震。蛇河平原（SRP）中的年龄增强火山（热点轨道）的对齐是SW-NE，同意北美板块的板块运动，这表明黄石热点可能是羽毛，它可能是羽绒，它来自夏威夷热点，例如夏威夷热点。然而，高熔岩平原（HLP）中的火山在NW方向上形成了一个热点轨道，该轨道针对李子假设。双峰热点轨道的机制和PNW中的大量岩浆作用仍在争论中。美国西北部下面的地震速度模型以前的地震速度模型已提高了对该地区复杂地质学的理解。地震波的速度也取决于其传播方向，称为地震各向异性，这与岩石圈变形和地幔流有关。因此，成像地震各向异性对于理解地球的动态地幔过程至关重要。研究人员将在太平洋西北部生产高分辨率的3D地震各向异性模型，以解决板块 - 锅中的相互作用及其对广泛火山的贡献。该模型还有助于理解和监测该地区的地震性和火山爆发。该项目将培训一名研究生和一名本科生，从事地震数据处理和层析成像方法。该研究结果将通过会议，期刊和网站与科学界共享，并在调查员的本科生和研究生课程中与少数派服务机构的学生分享。海洋板块俯冲，后弧火山和热点活动塑造了西北太平洋的地质历史。使用来自USArray可运输阵列（TA）的数据开发了许多高分辨率地震模型，从而提高了我们对该地区构造和地球动力学的理解。但是，沿SRP和HLP的宽度岩浆作用的来源是来自地幔羽还是侵入热的海洋运动层。许多局部速度异常意味着该区域中复杂的小规模地幔转换，在当前各向异性模型中尚未验证，横向或垂直分辨率有限。研究人员将使用瑞利（Rayleigh）和爱地震中的爱情波数据构建高分辨率各向异性模型，该模型记录在美国西北部的TA和其他共存站。在这些模型中，径向和方位角各向异性的分辨率与各向同性速度相似，有助于揭示详细的地幔动态过程和测试对西北太平洋地区地球物理观察的可能机制。该奖项通过评估了NSF的法定任务，反映了NSF的法定任务，并通过评估了基金会的范围，并已将其视为支持者的支持。