Natural Earthquake Laboratory in South African Mines (NELSAM)

这是一个研究地震震源深度孕震过程的项目。这将在南非的深部金矿进行，这些金矿具有独特的优势：(1)采矿作业控制着地震的地点、震级和时间，调查可以集中在有地震保证的地点；(2)矿山基础设施允许进入孕震断层，并允许在距离震中1-100米的地震之前、期间和之后监测断层活动；(3)矿山地震(M=3-4)的规模弥合了实验室使用的小样本(M0)和沿地壳断层的大地震(M6)之间的差距；(4)可以监测灾难性地震对地下生命(微生物生态)的影响。南非的地雷本质上是一个天然地震实验室，有机会通过对地震过程的近场三维监测为地震科学作出基本贡献。具体来说，该项目将涉及：(1)在矿山深度1.5-3.0公里的三个活动断裂带进行钻探。将选择断层以优化研究的结构和地震活动；即，在项目的生命周期内，它们将很有可能发生中、小型地震；(2)将部署密集的仪器阵列，以监测地震的三维、近场过程。这些仪器将包括地震仪、应变计、温度传感器、位移仪，以及监测强地面运动、电磁辐射、声发射、微生物群落和断层流体和气体化学的时间变化的设备；以及(3)活动断裂的物理和化学条件将通过地应力测量和三维制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