Natural Earthquake Laboratory in South African Mines (NELSAM)

0409605研究这是一个研究地震震源深度处孕震过程的项目。 这项工作将在南非的深层金矿进行，这些金矿具有独特的优势：（1）采矿作业控制地震的位置、震级和时间，调查可以集中在保证发生地震的地点;（2）矿井基础设施允许进入地震产生的断层，并允许在地震发生前监测断层活动，（3）矿震（M = 3-4）的大小弥补了实验室小样本（M0）与沿沿着地壳断层的大地震（M6）之间的差距;（4）可以监测大地震对地下生物（微生物生态）的影响。 南非的矿山实际上是一个天然地震实验室，有机会通过近场三维监测地震过程对地震科学作出根本性贡献。 具体而言，该项目将包括：（1）钻穿矿井中1.5 - 3.0公里深处的三个活动断层带。 选择断层是为了优化结构和地震活动，以便进行研究;也就是说，在项目的生命周期内，它们很有可能发生小到中等地震;（2）将部署密集的仪器阵列，以监测地震的三维近场过程。 这些仪器包括地震仪、应变仪、温度传感器、位移计，以及监测强地面运动、电磁辐射、声发射、微生物群落的时间变化以及断层流体和气体化学的装置;（3）活动断层的物理和化学条件将通过原地应力测量和三维绘图以及广泛的化学和岩石力学来表征

0409605RechesThis is a project to investigate seismogenic processes at the focal-depth of earthquakes. This will be conducted in the deep gold mines of South Africa that offer unique advantages: (1) Mining operations control the location, magnitude and timing of the earthquakes and the investigation can be focused at sites where earthquakes are guaranteed; (2) The mine infrastructure allows access to earthquake-producing faults and permits monitoring fault activity before, during and after earthquakes at distances of 1-100 m from the hypocenter; (3) The size of mine earthquakes (M = 3-4) bridges the gap between the small samples used in the laboratory (M0) and large earthquakes along crustal faults (M6); and (4) The effects of catastrophic earthquakes on subsurface life (microbial ecology) could be monitored. The South African mines are, in essence, a natural earthquake laboratory with opportunities to make fundamental contributions to earthquake science by near-field, three-dimensional monitoring of the earthquake process. There is no other natural environment where this is possible.Specifically, the project will involve: (1) Drilling through three active fault zones at depths of 1.5 - 3.0 km in mines. The faults will be chosen to optimize the structure and seismic activity for research; i.e. they will have a high probability of generating small to moderate earthquakes during the life of the project; (2) A dense array of instruments will be deployed to monitor the three-dimensional, nearfield processes of the earthquakes. The instruments will include seismometers, strainmeters, temperature sensors, displacement-meters, and devices to monitor strong-ground motion, electromagnetic radiation, acoustic emission, and time-variations of microbial communities and fault fluid and gas chemistry; and (3) The physical and chemical conditions of the active faults will be characterized by in-situ stress measurements and 3D mapping, and by extensive chemical and rock mechanics