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

边缘：合作研究：海湾伸展省和下加利福尼亚州下方地壳和上地幔的 3-D 断层扫描

• 批准号: 0718418
• 负责人: Brian Savage
• 金额: --
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-11 至 2010-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0718418&HistoricalAwards=false
• 关键词: MARGINS; Collaborative; Research; Tomography; Crust

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.

智力影响。建议构建一个三维高分辨率模型，描述加利福尼亚湾伸展省（GEP）和邻近下加利福尼亚州下方的地壳和上地幔的剪切速度结构。主要目标是对俯冲法拉隆板块的残余物进行成像，寻找半岛山脉基岩下方岩石圈分层的证据，估计岩石圈的厚度，绘制上地幔熔体生产区域的地图，并将地壳厚度变化模型扩展到地震折射或接收函数研究未成像的区域。总体而言，这些观测结果将有助于了解岩浆生成以及下加利福尼亚州与大陆其他地区裂谷的过程。开发模型的策略是一个逐步迭代的过程，涉及：（1）利用通过海湾周围的台站阵列传播的远震表面波，采用新的阵列处理技术和有限频率响应内核，开发该地区的中等分辨率 3D 模型； (2) 整合地震折射实验、重力、面波频散噪声相关测量和接收函数分析推断的地壳结构信息，并根据构造省、地质图和地形进行插值； (3) 通过比较全 3D 模型中生成的观测波形和合成波形，使用区域地震的地震图来完善该模型，该模型采用运动方程来计算完整的弹性响应。该模型将迭代完善，直到地震图完全匹配。拟议的研究通过以下方式解决了 MARGINS 大陆岩石圈破裂倡议的三个首要主题：（1）绘制由于岩石圈拉伸和扩张而导致的地壳厚度变化； (2) 绘制岩石圈地幔部分的表观厚度图，包括与破裂引发过程密切相关的大洋岩石圈俯冲碎片； (3) 对地幔中异常低剪切速度的区域进行成像，这些区域对应于岩浆生成的可能区域。更广泛的影响。作为 MARGINS 科学计划的一部分，这项研究将有助于了解大陆裂谷和相关火山活动的机制。该项目将促进与下加利福尼亚州和海湾外延省工作的地球科学家的合作。 PI 将与 MARGINS 办公室合作，帮助向更广泛的公众传播他们的结果。研究区域内波传播的影片以及峰值地面速度和加速度的地图将与补充课程材料、示例、文档和元数据一起可供下载。这些地图可用于地震灾害评估。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。