Collaborative Research: Magnetotelluric Investigation of the Salton Trough

合作研究：索尔顿海槽的大地电磁调查

• 批准号: 2243695
• 负责人: Steven Constable
• 金额: $ 31.75万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2243695&HistoricalAwards=false
• 关键词: Collaborative; Research; Magnetotelluric; Investigation; Salton

The Salton Trough, a low-lying arid region surrounding and including the Salton Sea in Southern California, is tectonically complex, where all three plate margin types, transform, divergent and convergent, come together. This project addresses key questions in the region, including the location of the active plate margin, the composition of the rocks, the role do fluids sourced from great depth and high crustal temperatures in shaping earthquake and volcanic hazards in the area. The researchers will employ a geophysical tool, both on-land and within the Salton Sea, that is capable of recording tiny fluctuations in the Earth’s natural electromagnetic field and extract from these data estimates of subsurface electrical conductivities, i.e., how well the rocks and materials conduct electric currents. This information will then be translated to rock composition to depths greater than 100 km, fluid pathways and concentrations from these depths to mapped surface faults and volcanic targets, temperature variations, and fault dimensions and geometries, all with the aim of better defining the Salton Trough’s unique tectonic architecture. In addition to informing local seismic and volcanic hazards, broader impacts will include the education of two graduate students, a postdoctoral scholar, and local high schoolers during field campaigns as well as building connections between tectonic activity and the potential and prevalence of critical minerals (e.g., lithium) being explored in this area at present.The Salton Trough is an exemplary case of the confluence of all three plate tectonic margin types, combining the southern San Andreas fault system (SSAF, transform) interrupted by localized incipient rifting (divergent) and abutted to the west by the Peninsular Ranges, a remnant of Farallon slab subduction (convergent). All these systems contribute to a region of complex structure and strain, rich in aqueous fluids and melts, and play key roles in the potential for destructive earthquakes along the critically strained SSAF and volcanic activity in the area. The research team will image and inform this tectonically complex region by deploying multi-scale (sites 100s m to 10s km apart) and amphibious (including the Salton Sea) magnetotelluric arrays and extracting electrical conductivity information from the surface into the uppermost asthenosphere. At the largest scale (10 km) this information will address questions on variations in lithospheric-scale fabric, the lithosphere-asthenosphere boundary and dehydration of the subducted Farallon slab. The focus of the mid-scale deployments will be crustal and uppermost mantle composition, the partitioning of fluids, partial melt, and by inference strain, and the evolution of these properties from transform to incipient rifting areas. At the finest scales (stations 1 km apart), the imaged conductivities will help highlight fault zone porosity, fluid content and attitudes and how these differ between creeping (e.g., SSAF) and locked fault strands. These multi-scale estimates, combined with existing geoscientific knowledge, will provide a more holistic understanding of local tectonics and its related geohazards.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.

索尔顿槽是一个围绕南加州的索尔顿海的低洼干旱地区，在构造上是复杂的，在那里所有三个板缘类型，转化，发散和收敛性，都聚集在一起。该项目解决了该地区的关键问题，包括活动板边缘的位置，岩石的组成，液体的作用是从深度和高地壳温度中得出的，在塑造该地区的地震和火山危害中。研究人员将采用地球物理工具，无论是陆上还是在索尔顿海内部，能够记录地球自然电子场中的微小波动，并从这些数据估计的地下电导率估算中提取，即岩石和材料的良好性能传导电流。然后，这些信息将转化为岩石组成，深度大于100 km，流体途径以及从这些深度到映射的表面故障和火山靶标的，温度变化以及断层尺寸和几何形状的浓度，所有这些都以更好地定义Salton wolds salton槽的独特构造结构。除了告知当地的地震和火山危害外，更广泛的影响还将包括对两名研究生的教育，一门学术科学的教育以及在现场活动期间的当地高中生的教育，以及建立构造活动与关键矿物的潜在和普遍性之间的联系（例如，目前都在此范围内探索的salton Foursons confortion。南部圣安德烈亚斯断层系统（SSAF，变换）被局部起步成熟（发散）中断，并由半岛范围伸入西部，这是法拉隆板俯冲（收敛）的残余。所有这些系统都促成了复杂的结构和应变区域，富含水笛和融化，并在沿该地区严重紧张的SSAF和火山活动沿破坏性地震的潜力中起关键作用。研究团队将通过部署多尺度（相距100s至10 km）和两栖（包括索尔顿海）磁阵列并将电导率信息从表面中提取到最高运动层的磁电导率信息，从而形象并告知该构造复杂区域。在最大范围（10 km）上，此信息将解决有关岩石圈尺度织物，岩石圈 - 心圈边界和俯冲Farallon板的脱水的问题。中尺度部署的重点将是地壳和最上面的地幔组成，流体的分配，部分熔体和通过推理应变，以及这些特性从变换到初始成熟区域的演变。在最佳尺度（相距1公里）的情况下，成像的电导率将有助于突出断层区的孔隙率，流体含量和与会者，以及它们之间的蠕变（例如SSAF）和锁定的断层链之间的不同之处。这些多尺度估计以及现有的地质知识将对当地构造及其相关的地球扎士提供更全面的理解。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响审查标准通过评估来获得的支持。