Falling Basins: revealing hidden faults from patterns of land subsidence from water extraction using Earth Observation data

世界各地仍有许多地震断层有待发现，有时是因为它们隐藏在景观中，被盆地中的沉积物覆盖。城市建在这些盆地上，因为它们为农业提供了肥沃的土地，并提供了地下水资源。然而，地下水的开采会导致严重的地面沉降。虽然这是一个住房和供水问题，但它提供了一个重要的机会，可以找到城市地下可能构成未来地震风险的断层。我们可以检测到这些断层，因为它们优先控制地下水在地下和含水层中的流动，因此对地表下沉的结构控制。利用最新的地球观测卫星，如哨兵1号，该项目将探测这些沉降模式，以使用干涉合成孔径雷达技术找到世界各地主要城市下方的隐藏断层（埃利奥特，2020年）。我们预计，包括水平以及垂直运动将提高沉降和故障位置的检测。这项工作很重要，因为地震危险和隐藏的断层可能会影响到不断发展的城市中的许多人（Crowley & Elliott，2012）。许多主要断裂沿着分布在山脉和盆地的边缘，并容纳了这两个构造域之间的相对运动。然而，随着变形随时间迁移，断层也在盆地内形成，并且断层可能隐藏在盆地内（Elliott等人，2020年）。这项研究将是跨学科的，直接与灾害风险和人道主义工作者接触，以调整相关的科学产出，纳入灾害风险评估和紧急情况规划。因此，这将有助于实现可持续城市的联合国发展目标，减少灾害造成的生命损失。通过对人为地面沉降模式进行限制的多孔弹性模型（Gambolati & Teatini，2015），将更好地了解地下水抽取的地质力学影响和流体流动断层的控制。现在，利用哨兵1号等卫星雷达，可以逐步改变对区域性地区变形的空间和时间模式的观测，利用干涉合成孔径雷达，每年的精度优于几毫米。该项目将使用这些基于空间的差异沉降率测量来测试揭示活跃变形地区城市下方隐藏断层的方法。它将检验这一假设，即除了垂直速率外，还通过对观测结果的直接成像和计算机视觉分析以及含水层流动的数值模型，利用水平变形大大增强了断层探测。通过量化沉降的空间和时间模式，使用独立成分分析等数据分析技术，可以识别沉积物中潜在的隐藏断层。通过将其与全盆地沉降压实模型的地表变形预测进行比较，将检测到作为流体流动障碍或管道的断层，因为这些断层将改变一阶沉降信号。一旦确定，将与关键利益相关者共同设计断层相对于暴露的城市人口的位置和大小，以使用基于地震的方法进行应用地震危害和风险分析（Hussain等人，2020).该学生将在利兹地球与环境学院地球物理与构造研究所活动构造组的约翰·埃利奥特博士的监督下工作。该项目将由Mark托马斯博士（也在IGT，SEE）和Kate Crowley博士（爱丁堡大学）共同监督。位于利兹的地球物理与构造研究所也是地震、火山和构造观测与建模中心（COMET）的所在地，该中心提供了一大批从事积极技术研究的研究人员。

Many earthquake faults remain to be discovered around the world, sometimes because they are hidden in the landscape, covered by sediments in basins. Cities are built on these basins because they offer fertile ground for agriculture and sources of water contained within the ground. However, groundwater extraction can induce significant land subsidence. Whilst a problem for housing and water supply, it provides an important opportunity to find faults beneath the city that may pose a future earthquake risk.We can detect these faults as they preferentially control how ground water flows in the subsurface and within aquifers, and consequently exhibit a structural control on how the ground surface sinks. Using the latest Earth Observation satellites, such as Sentinel-1, this project will detect these subsidence patterns to find the hidden faults beneath major cities around the world using the technique of InSAR (Elliott, 2020). We anticipate that including horizontal as well as vertical motion will improve detection of subsidence and fault locations. This work is important because seismic hazard and hidden faults potentially affect many people in growing cities (Crowley & Elliott, 2012). Many major faults lie along the edge of mountains and basins, and accommodate the relative motion between these two tectonic domains. However, faults also form within basins as the deformation migrates through time and the fault may be hidden within the basin (Elliott et al., 2020). This research will be interdisciplinary and engage directly with disaster risk and humanitarian practitioners to tailor relevant science-based outputs for integration within disaster risk assessment and emergency scenario planning. This will therefore support the realisation of UN development goal of sustainable cities and reduced loss of life from hazards.An improved understanding of the geomechanical effects of groundwater withdrawal and the control of faults of the flow of fluids will be gained through poro-elastic modelling (Gambolati & Teatini, 2015) placing constraints on the patterns of anthropogenic land subsidence. A step change in observing spatial and temporal patterns of deformation over regional areas is now possible with satellite radar such as Sentinel-1, with accuracies better than a few millimetres per year using InSAR. This project will use these space-based measurements of differential subsidence rates to test methods that reveal these concealed faults beneath cities in actively deforming regions. It will test the hypothesis that fault detection is greatly enhanced with the use of horizontal deformation in addition to vertical rates, both through direct imagery and computer vision analysis of the observations and in numerical models of aquifer flow. By quantifying the spatial and temporal pattern of subsidence, using such data analysis techniques as Independent Component Analysis, identification of potential hidden faults within the sediments will be possible. By comparing this to predictions of surface deformation from basin-wide compaction modelling of subsidence, the faults acting as barriers or conduits to fluid flow will be detected as these will alter the first-order subsidence signal. Once identified, the locations and sizes of faults relative to exposed urban populations will be co-designed with key stakeholders to produce applied seismic hazard and risk analyses using a scenario-based approach (Hussain et al., 2020).The student will work under the supervision of Dr. John Elliott, within the Active Tectonics group of the Institute of Geophysics & Tectonics in the School of Earth & Environment at Leeds. The project will be co-supervised by Dr Mark Thomas (also in IGT, SEE) and Dr Kate Crowley (University of Edinburgh). The Institute of Geophysics & Tectonics at Leeds also hosts the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET) which provides a large group of researchers engaged in active tec