One of the most difficult challenges in underground mining is to forecast significant seismic events prior to their occurrence in order to support the safety of miners and to minimize damage to the underground operation. Passive seismic tomography is a tool to image the seismic velocity changes in a rockmass, which can potentially reveal the rockmass behavior before and after a significant seismic event. In this paper, the changes in seismic velocity of the rockmass before and after three major seismic events are investigated to determine whether there are identifiable precursory velocity changes associated with the major seismic events. Conventional mechanics imply that the induced stress at the hypocenter would continue increasing until failure, in the form of an induced seismic event, occurs. With passive seismic tomography we can image changes to the seismic wave velocity distribution within a rockmass and hence infer the changes to the induced stress near the hypocenter. This paper evaluates the hypothesis that induced stress at the hypocenter (as inferred by the p-wave velocity) increases until the seismic event occurs. In addition to analyzing p-wave velocity changes near the hypocenter, changes to the p-wave velocity at “zone centers” were also analyzed. These “zone centers” are regions within the rockmass that consistently have a p-wave velocity that is much higher than the average p-wave velocity for the rockmass. It is found that the p-wave velocity did not increase at any of the three hypocenters prior to the seismic event occurring, however the p-wave velocity did increase in the closest “zone center” for two of the three events.

中文翻译：

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深、窄脉矿与三大地震事件相关的地震波速度变化的时变监测

地下采矿中最困难的挑战之一是在重大地震事件发生之前对其进行预测，以支持矿工的安全并尽量减少对地下作业的损害。被动地震层析成像是一种对岩体中地震速度变化进行成像的工具，它可以潜在地揭示重大地震事件前后岩体的行为。本文通过研究三个主要地震事件前后岩体地震速度的变化，以确定是否存在与主要地震事件相关的可识别的前兆速度变化。传统力学意味着震源处的诱发应力将继续增加，直到以诱发地震事件的形式发生故障。通过被动地震层析成像，我们可以对岩体内地震波速度分布的变化进行成像，从而推断震源附近诱发应力的变化。本文评估了震源处的诱导应力（由 p 波速度推断）增加直到地震事件发生的假设。除了分析震源附近的 p 波速度变化外，还分析了“区域中心”的 p 波速度变化。这些“区域中心”是岩体中始终具有远高于岩体平均 p 波速度的 p 波速度的区域。发现在地震事件发生之前，三个震源中的任何一个的 p 波速度都没有增加，