MARGINS: Collaborative Research: 3-D Tomography of the Crust and Upper Mantle Beneath the Gulf Extensional Province and Baja California

智力上的影响。建立了加利福尼亚州海湾伸展省(GEP)及其邻近的下加利福尼亚州地壳和上地幔剪切速度结构的三维高分辨率模型。主要目标是对俯冲的法拉隆板块的残留物进行成像，寻找半岛山脉岩基之下岩石圈拆沉的证据，估计岩石圈的厚度，绘制上地幔熔体产生区的地图，并将地壳厚度变化的模型扩展到地震折射或接收函数研究没有成像的地区。总体而言，这些观察将有助于理解岩浆产生和下加利福尼亚与大陆其他地区裂谷相关的过程。发展模式的战略是一个循序渐进的迭代过程，包括：(1)采用新的阵列处理技术和有限频率响应核，利用远震面波传播穿过墨西哥湾周围的台阵，建立该区域的中分辨率三维模式；(2)综合从地震折射实验、重力、面波频散的噪声相关测量和接收函数分析中推断出的地壳结构信息，并根据构造省、地质图和地形进行内插；以及(3)使用区域地震的地震图，通过比较在全三维模型中产生的观测和合成波形来完善该模型，该模型使用运动方程来计算完整的弹性响应。模型将反复改进，直到地震记录得到很好的匹配。这项拟议的研究涉及边缘大陆岩石圈破裂倡议的三个主要主题：(1)绘制由于岩石圈拉伸和扩张而导致的地壳厚度的变化；(2)绘制岩石圈地幔成分的视厚度，包括与破裂起始过程密切相关的大洋岩石圈的俯冲碎片；以及(3)对应于可能的岩浆生成区域的地幔中剪切速度异常低的成像区域。作为边缘科学计划的一部分，这项研究将有助于理解大陆裂谷和相关火山作用的机制。该项目将促进与致力于下加利福尼亚州和海湾延伸省的地球科学家的合作。采购经理将与边际办公室合作，帮助向更广泛的公众传播他们的结果。研究区域内的波传播电影和峰值地面速度和加速度地图将与补充课程材料、示例、文档和元数据一起提供下载。这些地图在地震危险性评估中很有用。该项目将支持一名研究生和至少一名本科生作为兼职或暑期研究助理的教育。

Intellectual Impact. It is proposed to construct a three-dimensional, high resolution model of the shear-velocity structure of the crust and upper mantle beneath the Gulf of California Extensional Province (GEP) and neighboring Baja California. Primary goals are to image remnants of the subducted Farallon plate, search for evidence of lithospheric delamination beneath the Peninsular Range batholith, estimate thickness of the lithosphere, map regions of melt production in the upper mantle, and extend models of crustal thickness variations to areas that are not imaged by seismic refraction or receiver function studies. Overall, these observations will help in understanding the processes involved in magma generation and rifting Baja California from the rest of the continent. The strategy for developing the model is a step-wise, iterative process involving: (1) development of a moderate-resolution 3-D model of the region using teleseismic surface waves propagating through the array of stations surrounding the Gulf, employing new array processing techniques and finite frequency response kernels; (2) integration of information on crustal structure inferred from seismic refraction experiments, gravity, noise correlation measurements of surface wave dispersion, and receiver function analysis, with interpolations based on tectonic province, geological maps and topography; and (3) use of seismograms from regional earthquakes to refine this model by comparing observed and synthetic waveforms generated in a fully 3-D model that employs equations of motion to calculate the complete elastic response. The model will be refined iteratively until the seismograms are well matched. The proposed study addresses three of the overarching themes of the Rupturing Continental Lithosphere initiative of MARGINS by (1) mapping variations in crustal thickness due to lithospheric stretching and spreading; (2) mapping apparent thickness of the mantle component of the lithosphere, including subducted fragments of the oceanic lithosphere that were intimately involved in the rupture initiation process; and (3) imaging regions of anomalously low shear velocity in the mantle that correspond to probable regions of magma generation.Broader Impacts. As part of the MARGINS science program, this study will contribute to the understanding of the mechanisms involved in continental rifting and associated volcanism. The project will promote collaboration with geoscientists working on Baja California and the Gulf Extensional Province. The PIs will work with the MARGINS office to help disseminate their results to the wider public. Movies of wave propagation and maps of peak ground velocity and acceleration within the study area will be made available for download along with supplementary course material, examples, documentation, and meta-data. The maps can be useful in earthquake hazard assessment. This project will support the education of a graduate student and at least one undergraduate as a part-time or summer research assistant.