Time lapse seismic monitoring of rock stress and fluid saturation changes in the near-surface following an explosive event at depth

现场视察的主要目标是定位和确认可能表明UNE已经进行的现象和可观测量。由于这是一个地下事件，对地面零点（SGZ）周围感兴趣区域的特征描述以及对流体通过地质迁移的潜在路径的了解，将最大限度地提高现场视察期间成功进行放射性核素（RN）采样的机会。由于某些RN签名被视为核试验的“吸烟枪”，因此这是非常可取的。拟议的项目将是探索共振地震测量潜力的首批项目之一，这是一种基本上未定义和未开发的全面禁试条约技术，用于监测这种流体迁移。因此，它将是世界领先的，并将为条约和现场视察带来直接和切实的好处。它将使用地球物理监测方面的先进技术来评估地下的应力场，并监测SGZ附近的流体迁移。所提议的技术称为四维地震监测，它使用高精度设备探测地震速度随时间和空间的微小变化，这种变化是地下爆炸后动态应力变化（空洞塌陷和裂缝扩展）或流体迁移（地下水位恢复）的结果。这将涉及不同地质和源类型的计算建模，以确定应力场和预测的流体迁移，以及可能观察到这些的时间尺度。鉴于现场视察期间可用的时间和人力有限，优化调查设计。这将包括一项研究，以确定设备和数据处理的要求。作为这项工作的一部分，将与石油工业伙伴合作进行一系列实地试验。

The primary goal of an OSI is to locate and characterise phenomena and observables that might indicate that a UNE has been conducted. Since this is a subsurface event, characterisation of an area of interest surrounding Surface Ground Zero (SGZ), and an understanding of potential paths of fluid migration through the geology, will maximise the chances of successful radionuclide (RN) sampling during an OSI. Since certain RN signatures are seen as the "smoking gun" of a nuclear test, this is highly desirable.The proposed project will be one of the first to explore the potential of Resonance Seismometry - a largely undefined and unexploited CTBT technique - to monitor this fluid migration. As such it will be world-leading and will have direct and tangible benefits for the treaty and for OSI. It will use advanced techniques in geophysical monitoring to assess the stress field in the subsurface and monitor fluid migration in the vicinity of SGZ. The technique proposed is known as 4D Seismic Monitoring, which uses high-precision equipment to detect minute changes in seismic velocity over time and space, which occur as a result of dynamic stress changes (cavity collapse and fracture propagation) or fluid migration (water table recovery) following a subsurface explosion.The project will have two complementary streams:-Definition of a parameter space in which the technique could be used effectively during an OSI. This will involve computational modelling of different geologies and source types to determine the stress field and predicted fluid migration, as well as the timescales over which these might be observed.-Optimisation of survey design given the limited time and manpower available during an OSI. This will include a study to determine equipment and data processing requirements. As part of this work, there will be a series of field trials in collaboration with petroleum industry partners.