Assessment of Geohazards and Geodynamics by Integrated Gravimetric and Geodetic Methods

虽然可以利用若干地球物理和大地测量技术对地质灾害和地球动力学进行评估，但重力监测对估计地下质量变化和移动特别有效，尽管其分辨率低，解决办法也不独特。然而，重力法的应用已被限制在连续和长期监测微小的地下质量变化和迁移的地质CO2储存地点，油气藏和活动构造区，主要是因为传统的弹簧重力仪遭受相对较低的灵敏度和大的非线性漂移效应的机械弹簧。这些特征使得对解释和分析至关重要的非周期性重力信号的分析复杂化。此外，重力仪记录联合收割机结合了地表变形和地下质量变化的重力效应，而这两者必须分开。 这些限制可以通过综合重力测量和大地测量技术加以克服。超导重力仪，它使用磁悬浮球作为测试质量，具有相当低的漂移和高得多的灵敏度在时域和频域比弹簧或绝对重力仪。有了这些属性，超导重力仪提供了监测地质灾害和地球动力学所需的几十年时间内重力变化的精确和连续的记录。特别是，可以有效地从地表变形所造成的重力分量中分离出地表下质量变化的重力分量，这是使用从组合的持续散射体干涉SAR雷达遥感和其他卫星和近地表大地测量技术（如倾角计和全球导航卫星系统测量）精确建模的地表变形约束条件。 在这项研究中，我建议开发技术，以评估分钟和连续的质量变化和迁移不断综合重力和大地测量。超导重力仪是测量时变重力场的关键仪器，它与绝对重力仪和弹簧重力仪一起用于四维重力场和地下模拟。除了地下质量变化和运动之外，重力测量还包括与地下活动相关的地表变形的重力效应。将干涉合成孔径雷达技术与重力场相结合进行位移分析。所开发的技术将被应用于监测：1）同震和无声地震变形的卡斯卡迪亚俯冲带附近的温哥华岛，不列颠哥伦比亚省;和，2）迁移和泄漏的注入CO2在阿尔伯塔和萨斯喀彻温省的地质CO2存储站点。 虽然这一区域的构造活动在地球表面上是无声的，因为它们不会造成任何明显的破坏，但它们将使我们更好地估计加拿大西海岸的下一次大地震。这一活跃的构造带目前正在积聚应力，最终可能导致大地震和海啸。这些地质灾害将造成人员伤亡和财产损失。如果能够探测到大地震的前兆，这些前兆可以用于公共安全和政策制定。 在确保地质碳储存方面，对储存中的二氧化碳羽流进行定量跟踪并检测通过盖层或含水层的任何泄漏都非常重要，因此，需要一项全面的监测协议来确保碳储存。这项研究可能是唯一一个满足上述要求：监测地下质量变化，质量运动和地下储存泄漏。

Although assessments of geohazards and geodynamics are possible with a number of geophysical and geodetic techniques, gravity monitoring is especially effective for estimating subsurface mass change and movement despite its low resolution and non-unique solution. However, applications of the gravimetric method have been limited for continuous and long-term monitoring of minute subsurface mass change and migration at geological CO2 storage sites, hydrocarbon reservoirs and active tectonic zones, mainly because conventional spring gravimeters suffer from relatively low sensitivity and the large nonlinear drift effects of the mechanical springs. These characteristics complicate the analysis of the non-periodic gravity signals that are vital for interpretation and analysis. In addition, the gravimeter records combine the gravity effects of surface deformation and subsurface mass change that must be separated. These limitations can be overcome by integrated gravimetric and geodetic technologies. The superconducting gravimeter, which uses a magnetically levitated sphere as a test mass, has considerably lower drift and much higher sensitivity in the time and frequency domains than spring or absolute gravimeters. With these attributes, the superconducting gravimeter provides precise and continuous records of gravity variations over times to periods of decades that are required for monitoring geohazards and geodynamics. In particular, the gravity components from subsurface mass changes can be effectively separated from those caused by the surface deformations using surface deformation constraints accurately modelled from combined Persistent Scatterer Interferometric SAR (PSInSAR) radar remote sensing and other satellite and near-surface geodetic technologies, such as inclinometer and GNSS measurements. In this research, I propose to develop techniques to assess minute and continuous mass change and migration continuously by integrated gravimetric and geodetic measurements. The superconducting gravimeter is a key instrument for measuring the time-varying gravity, which is supported by absolute and spring gravimeters for 4D gravity and subsurface modelling. In addition to subsurface mass change and movement, the gravity measurements include the gravity effects from surface deformations associated with the subsurface activities. To analyze the displacement, InSAR technology will be integrated with gravity. The developed techniques will be applied to monitor: 1) co-seismic and silent earthquake deformation in the Cascadia subduction zone near Vancouver Island, BC; and, 2) migration and leakage of injected CO2 at Alberta and Saskatchewan geological CO2 storage sites. Although the tectonic events in this zone are silent on the Earth’s surface, in that they do not cause any noticeable damage, they will lead us to better estimates of the next great earthquake on the west coast of Canada. This active tectonic zone is currently accumulating stress that may eventually cause a great earthquake followed by a tsunami. These geohazards will cost human lives and cause property damage. If the detection of precursors of a major earthquake is possible, these precursors can be used for public safety and policy making. In terms of securing geological carbon storage, the tracking of the CO2 plume quantitatively in the storage and the detection of any leaks through the caprocks or aquifers are very important, and, hence, a comprehensive monitoring protocol is required for secure carbon storage. This research may be the only one that meets the above requirements: monitoring subsurface mass change, mass movement and leakage from the subsurface storage.