EAPSI:Aquifer System Storage Response to Canterbury Earthquake Sequence using Satellite Radar and Observation Well Time Series Data

2010-2011年新西兰坎特伯雷地震序列引发了显著的水文响应，表现为地面震动引起的地下水位变化。重要的是要了解含水层的储存能力在多大程度上受到影响，因为当地人口的饮用水供应依赖地下水。该奖项资助研究地震活动引起的含水层蓄水量变化的空间范围和幅度。该研究将与GNS Science首席科学家、著名构造和水文地质学专家西蒙·考克斯博士合作进行。通过分析地面隆起和井口水位的季节性模式，研究员将估算和比较地震序列之前、期间和之后的弹性含水层储水量。该项目将利用该地区丰富的卫星雷达和油井数据，作为研究含水层-地震相互作用的天然实验室。这一发现将影响其他地下水活跃使用的地震易发地区，包括南加州和田纳西州，以加强重大地震事件后的水管理计划。了解含水层系统与地震断层之间相互作用的时空范围是减轻液化相关危害和加强水管理计划的关键因素。为此，以足够的精度、时空分辨率和空间精度对地表变形进行成像是这项工作不可或缺的一部分。该研究员将使用来自ENVISAT和TerraSAR-X两颗SAR卫星的干涉合成孔径雷达（InSAR）数据集，进行上升和下降采集几何形状。重叠区域允许计算垂直和水平位移时间序列，捕获地震前、地震中和地震后的二维变形，包括构造和水文信号。此外，在坎特伯雷和克赖斯特彻奇地区有大量具有密集时间测量的观测井。通过比较垂直位移的孤立季节分量和观测井时间序列来估计弹性储存系数。为了分离信号中的季节分量，应用小波功率谱分析方法，对所需的季节时间序列进行识别、分离和重构。为了确定在地震序列中存储性是否增加或减少，在95%的置信区间内选择与输入相关的最佳拟合线性值。这项研究将以基督城和坎特伯雷平原为例，最终将帮助其他依赖地下水资源的地震灾害易发地区。该奖项由美国国家科学基金会和新西兰皇家学会共同资助，隶属于东亚和太平洋暑期研究所项目，支持一名美国研究生进行暑期研究。

The 2010-2011 Canterbury, New Zealand earthquake sequence prompted a significant hydrologic response in the form of groundwater level variations due to ground shaking. It is important to understand the extent to which the storage capacity of aquifers is affected, given the reliance of local populations on groundwater for drinking water supply. This award funds research to investigate the spatial extent and amplitude of the change in aquifer storativity due to the seismic activity. The research will be conducted in collaboration with Dr. Simon Cox, Principal Scientist at GNS Science and renowned expert in structural and hydrogeology. By analyzing seasonal patterns in ground uplift and well head levels, the fellow will estimate and compare elastic aquifer storativity before, during, and after the seismic sequence. This project will use the abundant satellite radar and well data available for the region, which acts as a natural laboratory to study aquifer-earthquake interactions. The findings will impact other earthquake prone regions with active groundwater usage, including Southern California and Tennessee, to enhance water management plans following major seismic events. Understanding the spatiotemporal extent of the interaction between aquifer systems and seismic faults is a key factor for mitigating hazards associated with liquefaction and enhancing water management plans. To this end imaging surface deformation with sufficient precision, spatiotemporal resolution, and spatial accuracy is integral to this effort. The fellow will use Interferometric Synthetic Aperture Radar (InSAR) datasets from two SAR satellites, ENVISAT and TerraSAR-X, in both ascending and descending acquisition geometries. The overlapping areas allow for calculating the vertical and horizontal displacement time series, capturing pre-, co-, and post-seismic deformation in two dimensions including both tectonic and hydrological signals. In addition, observation wells with dense temporal measurements are abundant in the Canterbury and Christchurch region. The elastic storage coefficient is estimated by comparing the isolated seasonal component of the vertical displacement and the observation well time series. To isolate these seasonal components in the signals, wavelet power spectra analysis is applied, and the desired seasonal time series is identified, isolated and reconstructed. To determine if any increase or decrease in storativity occurred during the earthquake sequence, a best-fit linear value relating the inputs is chosen within a 95% confidence interval. This study will use Christchurch and the Canterbury Plains as a case study that will ultimately help other regions prone to seismic hazards that rely on groundwater resources. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Royal Society of New Zealand.