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

项目摘要本项目将针对自然发生的地下水，以确定空间和时间的变化，在加州的三个地震活跃区的氦-二氧化碳特性。 这三个地区是圣哈辛托断层（SJF）和圣安德烈亚斯断层（SAF）-都在中央加州（霍利斯特-帕克菲尔德）和南部加州（科切拉谷）。 将绘制这三个地区的He-CO2变化的区域范围，特别注意靠近已知断层痕迹的地方。 本实验室以前开发的新仪器（SPARTAH）将部署在具有强地幔挥发性输入（如原始同位素3 He所记录的）的地点。 SPARTAH可以提供一个高分辨率的时间记录（小时到天）的He-CO2变化在延长的时期（月到年）。以下假设，理解溶解挥发物之间的关系，如He和CO2，和发生在加州的地震活动，将被解决：1。断层是幔源挥发分到达地表的主要通道。观察到的3 He/4 He将被用来确定是否断层作为深地壳/地幔上部和表面之间的高渗透率的途径，如果是这样，模拟他们的通量。 反过来，这将允许评估通量的变化是否与强烈的微震活动（SJF），几乎没有地震活动（南部SAF）和频繁到罕见的地震（Hollister-Parkfield）的区域相关。 2. CO2是导致深部超静水压的主要挥发相。 耦合CO2/3 He和d13 C的变化将被用来解决CO2到地幔和地壳成分。 将确定地幔CO2渗漏的主要地区，并将得出对深层渗透率的实际估计。 3.时间变化是波动记录的特征，与地震活动的发生有关。 迄今为止，很少或没有记录的时间变化的挥发性通量在地震活跃区。 这一缺陷将通过部署SPARTAH仪器加以解决，SPARTAH仪器将能够在（a）有地震活动时确定时间记录的目标部分，以测量He和CO2（同位素和相对丰度）的响应（如果有的话），以及（B）没有任何（重大）地震扰动的证据。 He-CO2背景记录的这些部分对于建立时间基线值至关重要。 氦-二氧化碳变化的时间记录将与非火山性震颤的发生进行比较-与SAF上的滑动相关-发生在每隔几天到几个月的频率范围内的突发中。 SPARAH设计用于在高泵送速率/压力下连续采集地下水样本，以便捕获此类事件。 该项目将与NSF资助的海洋科学教育卓越中心-加州（COSEE CA）联系，制定一项计划，将研究的影响扩展到学术界之外。 COSEE CA和Scripps已经与圣地亚哥联合学区建立了多方面的合作，以支持他们新的、全地区的高中地球科学项目。 这种合作的一个关键因素是合作，为地区地球科学教师提供持续的专业发展相结合，其中许多人在他们的专业领域之外教学，并与斯克里普斯当前的地球和海洋科学研究建立强有力的联系。 该项目将为15名教师举办为期一天的讲习班，以支持斯克里普斯/SDUSD的合作，该讲习班将介绍有关加州地震活动和当地板块构造的基本信息，并重点关注评估地震与地下水地球化学信号之间关系的项目结果。

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.