Collaborative Research: Comprehensive Analysis of Seismic Processes in a Deep South African Mine

地震物理学中的许多基本问题仍然没有得到解决，这主要是因为在获得高质量的近震源记录和获得可靠的震源参数方面存在困难。该项目的总体目标是提高对大范围(约-4至4级)地震震源过程的了解。我们正在对南非一个3.6公里深的矿山中几种不同类型的地震事件(地震、岩爆和爆炸)的震源特性进行详细的地震学调查。我们还将开展短场活动，记录震级范围极端和靠近断层结构的地震事件。将使用全源张量反演、二次矩分析和频谱方法来确定震源属性的综合集合，包括标量势/矩、震源机制、拐角频率、应变/应力降、辐射能量、破裂速度和震源时间函数。将专门致力于探测断层的各向同性分量。从理论上计算不同事件类型的预期辐射将有助于解释结果。将上述分析应用于小震级近源地震数据，将使我们能够获得地震物理许多方面的约束条件，包括成核过程、地震辐射的各向同性分量的盛行、破裂物理随事件震级或地质和矿产构造附近的变化，以及地震、爆炸和其他震源之间的震源参数差异。关于震源性质和尺度关系的高分辨率结果将有助于解决关于地震成核和破裂过程、实验室结果与天然断层的比例以及地震能量预算等方面的长期争议，从而对地震物理和岩石力学领域产生重大影响。此外，关于空间相关地震性质的研究结果将有助于决策何时何地暂停采矿活动以加强地下安全

Many fundamental questions in earthquake physics remain unresolved, largely because ofdifficulties in obtaining high-quality, near-source recordings of small earthquakes andderiving reliable source parameters. The overarching goal of this project is to provide animproved understanding of earthquake source processes for a wide magnitude range(approximately -4 to 4). We are performing detailed seismological investigations ofsource properties that characterize several distinct classes of seismic events (earthquakes,rockbursts, and blasts) in a 3.6 km deep South African mine. We will also conduct a shortfield campaign to record seismic events at the extremes of the magnitude range and inclose proximity to fault structures. Full source tensor inversions, second momentanalysis, and spectral methods will be used to determine comprehensive sets of sourceproperties including scalar potencies/moments, focal mechanisms, corner frequencies,strain/stress drops, radiated energies, rupture velocities, and source time functions.Special effort will be devoted to detecting isotropic components of faulting. Theoreticalcalculations of expected radiation from different event types will help in theinterpretation of results.Applying the above analysis to the small-magnitude, near source seismic data will allowus to obtain constraints on many aspects of earthquake physics including nucleationprocesses, the prevalence of isotropic components of seismic radiation, changes in thephysics of rupture with event magnitude or with proximity to geologic and miningstructures, and source parameter differences between earthquakes, explosions, and otherseismic sources. The high-resolution results on seismic source properties and scalingrelations will significantly impact the earthquake physics and rock mechanicscommunities by helping to resolve long-term controversies on earthquake nucleation andrupture processes, scaling of laboratory results to natural faults, and earthquake energybudgets, among others. In addition, the findings on spatially dependent seismic propertieswill be useful for decision-making concerning when and where to suspend miningactivities to enhance underground safety