Western Deep Levels Gold Mine, South Africa, As A Natural Laboratory For Studying Rock Deformation Processes

该项目计划研究南非威特沃特斯兰德盆地西部深部金矿2-4公里深处的活动岩石变形。首席调查员将广泛获得矿山运营商盎格鲁黄金有限公司的数据集。矿山的地质结构具有很好的特征，矿山经营者监测采矿活动的细节--因此，驱动地震活动的机制被认为是空间和时间的函数。监测地震响应将允许检查变形过程(例如，摩擦愈合)，这可能产生关于速率-状态和其他本构关系公式的适用性的重要信息。采矿地震学家收集由70多个数字三分量台站组成的地震数据，他们每天使用软件处理数千个单独的地震事件(确定地震矩、拐角频率、辐射能量以及位置和震级)。该项目将调查编目参数的准确性，扩展编目以包括矩张量，并纳入相对事件定位和相对矩-张量确定的算法。这些数据将被用来a)区分新压裂产生的事件与与先前存在的断层上的滑动有关的事件，b)研究事件序列，以及c)研究力矩、能量和拐角频率之间的频率-震级分布和比例关系。

This project proposes to study active rock deformation at depths of 2-4 km in the Western Deep Levels gold mines of the Witwatersrand basin, South Africa. The principal investigator will have wide access to data sets from AngloGold Ltd., the mine operator. The geological structure of the mines is well characterized and the mine operators monitor the details of the mining activities--hence, the mechanism that drives the seismic activity is known as a function of space and time. Monitoring the seismic response will allow examination of the deformation process (e.g., frictional healing), which may yield important information about the applicability of rate-state and other formulations of constitutive relationships. The mining seismologists collect seismic data comprising more than 70 digital, three-component stations, and they process thousands of individual seismic events daily using software (determining seismic moment, corner frequency, radiated energy, as well as location and magnitude). This project will investigate the accuracy of the cataloged parameters, extend the catalogs to include moment tensors, and incorporate algorithms for relative event location and relative moment-tensor determination. These data will be used to a) distinguish events generated by fresh fracturing from those associated with slip on preexisting faults, b) study event sequences, and c) investigate frequency-magnitude distributions and scaling relationships among moment, energy, and corner frequency.