Natural Earthquake Laboratory in South African Mines (NELSAM)

[409605]研究这是一个研究地震震源深度的发震过程的项目。这将在南非的深部金矿进行，这些金矿具有独特的优势：(1)采矿作业控制了地震的位置、震级和时间，调查可以集中在肯定会发生地震的地点；(2)矿山基础设施允许进入产震断层，并允许在距震源1 ~ 100 m范围内监测震前、震中和震后断层活动；(3)矿井地震（M = 3-4）的大小弥补了实验室小样本（M0）和沿地壳断层的大地震（M6）之间的差距；(4)可以监测特大地震对地下生命（微生物生态）的影响。从本质上讲，南非矿山是一个天然的地震实验室，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的贡献。没有其他自然环境能让这成为可能。具体而言，该项目将包括：(1)钻穿矿区1.5 - 3.0公里深度的三个活动断裂带。选取断层进行构造优化和地震活动性研究；即在工程项目的存续期内，它们极有可能产生小至中地震；将部署密集的仪器阵列来监测地震的三维近场过程。这些仪器将包括地震仪、应变仪、温度传感器、位移仪，以及监测强震运动、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；(3)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活动断层的物理和化学条件

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