Analysis of Hydraulic Seismicity at the TAG Hydrothermal Mound

abstractoce - 0647221知识价值。本项目将通过分析2003年7月至2004年3月在大西洋中脊（26度）TAG热液场进行的为期9个月的独特海底实验的地震活动数据，解决大型硫化物矿床流体流动力学的基本问题。一个由5个海底地震仪（OBS）组成的网络被部署在活跃的TAG土丘周围，该土丘的直径约为200米。这些地震仪检测到约40,000个短脉冲事件，这些事件似乎是由矿床内水力过程引起的流动事件，我们将对这些事件进行地震学分析，以评估关键问题，例如为热液循环提供通道的裂缝网络的几何形状，以及水力压裂过程中减压的储层体积。我们还在微震调查期间从活跃的TAG丘上的21个地点获得了出口流体温度时间序列数据，这将增强我们所提出的分析的科学回报。因此，流体诱发事件可以放在温度记录中观察到的扰动模式的背景下，这将使我们能够在单个大规模硫化物矿床的规模上研究断层/压裂与流体流动之间的关系，这在以前是不可能的。更广泛的影响。在断裂控制的深海热液系统中，矿物沉积长期集中在离散带中，导致块状矿床的产生。要知道这些沉积物的大小是非常困难的，因为它们位于海底深处的偏远位置，而且大多数沉积物都在地下，但这项研究将使我们能够确定提供浅层地下流动通道的裂缝的位置。了解流体循环的几何形状将对矿床的地下范围提供很好的约束。这些深海喷口区还支持外来的化学合成生物群落，它们从与富含金属的热液的化学反应中获得代谢能量。了解流体循环的几何结构也将有助于我们了解这些生态系统底部微生物居住的地下生物圈的物理特征。该研究还将有助于麻省理工学院/世界卫生组织海洋学联合项目一名学生的研究生教育和博士论文研究。

ABSTRACTOCE-0647221Intellectual Merit. This project will address fundamental issues regarding the mechanics of fluid flow within a massive sulfide deposit by analyzing seismicity data from a unique ocean bottom experiment conducted at the TAG hydrothermal field on the Mid-Atlantic Ridge (26degreesN) for 9 months from July, 2003 to March, 2004. A network of five ocean-bottom seismometers (OBS) was deployed around the perimeter of the active TAG mound, which has a diameter of ~200 m. These seismometers detected ~40,000 short, impulsive events that appear to be flow-induced events from hydraulic processes within the mineral deposit, and we will conduct seismological analyses of these events to assess key problems such as the geometry of the fracture network that provides pathways for hydrothermal circulation, and the volume of fluid reservoirs that decompress during hydrofracturing. The scientific payoff from our proposed analysis will be enhanced by the fact that we also acquired exit-fluid temperature time-series data from 21 sites on the active TAG mound during the microearthquake survey. The flow-induced events can thus be placed in the context of the perturbation patterns observed in the temperature records, which will allow us to study the relationship between faulting/fracturing and fluid flow at the scale of an individual massive sulfide deposit something that has never before been possible. Broader Impacts. Mineral deposition in fault-controlled deep-sea hydrothermal systems is focused in discrete zones over long periods of time, which leads to the generation of massive ore deposits. It can be very hard to know the size of these deposits because of their remote position on the deep seafloor, and because most of the deposit is underground, but this research will allow us to determine the location of the cracks that provide flow pathways in the shallow subsurface. Knowing the geometry of fluid circulation will provide excellent constraints on the subsurface extent of the mineral deposit. These deep-sea vent fields also support exotic chemosynthetic biological communities that derive metabolic energy from chemical reactions with the metal-rich hydrothermal fluid. Knowing the geometry of fluid circulation will also help us understand the physical characteristics of the subsurface biosphere inhabited by the microbes at the base of these ecosystems.The research will also contribute to the graduate education and doctoral thesis research of a student in the MIT/WHOI Joint Program in Oceanography.