Characterizing Temporal and Spatial Variability in Groundwater Helium-Carbon Relationships at Seismically-Active Regions of California

表征加利福尼亚地震活跃地区地下水氦-碳关系的时空变化

• 批准号: 1014236
• 负责人: David Hilton
• 金额: $ 28.88万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1014236&HistoricalAwards=false
• 关键词: Characterizing; Temporal; Spatial; Variability; Groundwater

Project AbstractThis project will target naturally-occurring groundwater to define both spatial and temporal variability in He-CO2 characteristics at three seismically active regions of California. The three regions are the San Jacinto Fault (SJF), and the San Andreas Fault (SAF) - both in Central California (Hollister-Parkfield) and southern California (Coachella Valley). The areal extent of He-CO2 variations in the three regions will be mapped paying particular attention to localities close to known fault traces. The new instrument previously developed in this lab (SPARTAH) will be deployed at sites with a strong mantle volatile input (as recorded by the primordial isotope 3He). SPARTAH can provide a high-resolution temporal record (hours-to-days) of He-CO2 variations over extended periods (months-to-years).The following hypotheses, central to understanding the relationship between dissolved volatiles, such as He and CO2, and the occurrence of seismicity in California, will be addressed: 1. Faults are the principal conduits to the surface for mantle-derived volatiles. Observed 3He/4He will be used to determine whether the faults act as high permeability pathways between the deep crust/uppermost mantle and the surface and, if so, to model their fluxes. In turn, this will allow evaluation of whether or not variations in fluxes correlate with regions of intense microseismicity (SJF), virtually no seismicity (southern SAF) and frequent-to-infrequent earthquakes (Hollister-Parkfield). 2. CO2 is the major volatile phase leading to super hydrostatic pressure at depth. Coupled CO2/3He and d13C variations will be used to resolve CO2 into mantle and crustal components. Major areas of mantle CO2 leakage will be determined and realistic estimates of permeability at depth will be derived. 3. Temporal variability characterizes the volatile record and is related to the occurrence of seismic activity. To date, there is little or no record of temporal variations in volatile fluxes in seismically-active regions. This deficiency will be addressed through deployment of the SPARTAH instrument which will enable targeting sections of the temporal record when there is (a) seismic activity - to gauge the response (if any) of the He and CO2 (isotopes and relative abundances), and (b) no evidence of any (major) seismic disturbance. These parts of the He-CO2 background record are essential to establish the temporal baseline value. The temporal record of He-CO2 variations will be compared with the occurrence of nonvolcanic tremor - associated with slip on the SAF - which occurs in bursts ranging in frequency from every few days to months. SPARAH is designed to sample groundwater at high pumping rates/pressures continuously so such events can be captured. This project will liaise with the NSF-funded Center for Ocean Science Education Excellence - California (COSEE CA) to develop a plan to extend the impact of the research beyond the bounds of academia. COSEE CA and Scripps have developed a multi-faceted collaboration with the San Diego Unified School District to support their new, district-wide, high school Earth Sciences program. A key element of this collaboration is partnering to provide a combination of on-going professional development for district Earth Science teachers, many of whom are teaching outside their area of expertise, and robust connections to current research in Earth and Ocean sciences at Scripps. The project will sponsor a 1-day workshop for 15 teachers in support of the Scripps/SDUSD collaboration that combines presentation of basic information on California seismicity and local plate tectonics with a focused look at project results on assessing the relationship between earthquakes and geochemical signals in groundwater.

摘要项目项目将针对自然存在的地下水，以定义加利福尼亚三个地震活跃地区HE-CO2特征的空间和时间变异性。 这三个地区是圣哈辛托故障（SJF）和圣安德烈亚斯断层（SAF），包括中部加利福尼亚州（Hollister -Parkfield）和南加州（Coachella Valley）。 三个区域中HE-CO2变化的区域范围将被映射，以特别关注接近已知断层痕迹的地方。 先前在本实验室（Spartah）开发的新仪器将部署在具有强烈地幔挥发性输入的站点（如原始同位素3HE所记录）。 Spartah可以提供长期的HE-CO2变化的高分辨率时间记录（每小时）。观察到的3HE/4HE将用于确定断层是否作为深皮/最上层地幔和表面之间的高渗透率的作用，如果是的，则是对它们的通量建模。 反过来，这将允许评估通量的变化是否与强烈的微震（SJF）区域相关，几乎没有地震性（Southern Saf）和频繁到频率的地震（Hollister-Parkfield）。 2。CO2是导致深度超级静水压力的主要挥发相。 耦合的CO2/3HE和D13C变化将用于将CO2解析为地幔和地壳成分。 将确定地幔二氧化碳泄漏的主要区域，并将得出深度渗透率的现实估计。 3。时间变异性是挥发性记录的特征，与地震活性的发生有关。 迄今为止，地震活性区域挥发性通量的时间变化几乎没有记录。 这种缺陷将通过部署Spartah仪器来解决，该仪器将在（a）具有（a）地震活动时实现时间记录的段落 - 衡量HE和CO2的响应（如果任何）（同位素和相对丰度），以及（B）任何（主要）地震干扰的证据。 HE-CO2背景记录的这些部分对于建立时间基线值至关重要。 将He -CO2变化的时间记录与非volcanic震颤的发生（与SAF上的滑动相关的发生）进行比较，该震颤的发生频率从每隔几天到几个月就发生在频率范围内。 Sparah旨在连续以高泵送速率/压力采样地下水，以便可以捕获此类事件。 该项目将与NSF资助的海洋科学教育卓越中心 - 加利福尼亚州（Cosee CA）联络，以制定一项计划，以扩展研究的影响超出学术界的范围。 Cosee CA和Scripps与圣地亚哥统一学区建立了多方面的合作，以支持其新的，全区的高中地球科学计划。 这项合作的一个关键要素是合作，为地区地球科学教师提供了持续的专业发展，其中许多人在其专业领域的教学以及与斯克里普斯（Scripps）的地球和海洋科学研究的牢固联系。 该项目将为15名教师提供为期1天的研讨会，以支持Scripps/SDUSD合作，该研讨会结合了有关加利福尼亚地震性和本地板块构造的基本信息的介绍以及对项目结果的重点研究，以评估地下水中地震和地球化学信号之间的关系。