Groundwater overexploitation is a critical issue in the North China Plain (NCP), resulting in groundwater level decline and surface subsidence for the last half-century. This problem, however, has been greatly alleviated by the South-to-North Water Diversion (SNWD) Project since 2015. Monitoring of this process has been steadily improved in recent years using water level and geodetic observations. Here, we characterize the water storage change at the Huairou groundwater reserve site (HGRS) in Beijing due to the SNWD by combining Interferometric Synthetic Aperture Radar (InSAR) data of the Sentinel-1 satellites, continuous Global Positioning System (GPS) data, and well water level data observed during the same time. InSAR observations revealed subsidence up to ~400 mm in the Beijing plain but uplift at ~40 mm in the HGRS during 2015–2019, and more than 70% of the uplift occurred from October 2018 to January 2019. By integrating the most significant uplift deformation during October 2018 to January 2019 with water level observations at the same time, we estimated the storativity of the confined aquifer system at HGRS as $1.68–7.82\times {10}^{-3}$, weighing in the correction for effective stress and surface deformation for various situations. Based on the estimated aquifer storativity and the observed water level change in the unconfined and confined aquifer, the recharged water storage for the confined and unconfined aquifers was estimated as $1.20–1.39\times {10}^7{ \mathrm{m}}^3$ and ~$2.86\times {10}^8{ \mathrm{m}}^3$ from 6 October 2018 to 22 January 2019, respectively, which is about 4% and 91% of the surface water recharge through river channels in the same period due to the SNWD Project. Our study demonstrates that integration of geodetic and hydrological data can provide crucial information for the assessment of groundwater circulation and assistance of groundwater management.

Groundwater flow could produce an observable self-potential (SP) signal; it is, therefore, useful to use SP signal to investigate the condition of water flow, which is meaningful to the processes to which the water flow is critical, such as landslide warning, contaminant transport, and volcanic eruption. Most of the SP data inversion methods are based on prior in situ electrical resistivity information, which is difficult to be accurately obtained in the continuous monitoring of the vadose zone. We suggest a fusion scheme of integrating the electric charge occurrence probability (ECOP) tomography and the continuous complex wavelet transform (CCWT) method to process and interpret SP data when it lacks prior electrical structure information on the background media. A model of fracture flow with precipitation recharge is used to testify our proposed method. The results indicate that the combination scheme can locate the source of SP anomalies with improved accuracy. The proposed fusion probability tomography can locate the fracture flow with an explicit region of probability anomaly and suppress the irrelevant noises.

The occurrence of seismic events can be modulated by external periodic stress perturbations, such as daily tidal stress and annual hydrological stress. Such periodic modulations are crucial for understanding earthquake triggering, yet their underlying physical mechanisms are not fully understood. Here, we find that ordinary earthquakes (OEs) and low-frequency earthquakes (LFEs) on the Central San Andreas Fault (CSAF) are more sensitive to the long-period hydrological and the short-period tidal loadings, respectively. These different frequency-dependent modulations suggest pore fluid diffusion during the noninstantaneous earthquake nucleation and confirm different nucleation times of OEs and LFEs. We constrain the depth-varying physical properties of the CSAF and reveal that fluid content distribution and loading conditions fundamentally control slow-to-fast fault slip behaviors. Our study provides an alternative perspective to understand earthquake nucleation by using the information in periodic seismicity modulations, which can be applicable to subduction zones where similar slip behavior transitions occur.

Climatic and anthropogenic changes are reshaping global water resources, with the North China Plain (NCP) experiencing significant surface subsidence due to severe groundwater overexploitation over the past half‐century. In this study, we integrate data from Interferometric Synthetic Aperture Radar, Global Navigation Satellite System, and hydraulic head measurements observed in 2015–2019 to investigate aquifers' physical properties and corresponding changes in groundwater storage in NCP. Geodetic measurements indicate seasonal and long‐term deformation patterns. The amplitude of seasonal variation of deformation is up to 25 mm with phase lag behind the seasonal variation of water head. The integration of geodetic and hydrological data indicates that local aquifer storativity and clay lens thickness are and m, respectively. The average long‐term subsidence due to sustained water storage loss is about 29 mm/yr, with a peak rate of ∼120 mm/yr. Even though all regions show a long‐term ongoing subsidence, the subsidence trend has slowed in about half of the NCP, which can be attributed to the impact of the South‐to‐North Water Diversion (SNWD) Project, especially in areas near the SNWD aqueducts. Moreover, we find a disparity in subsidence rates between Hebei and Shandong Provinces, reflecting the impact of different groundwater exploitation management in mitigating the subsidence. This research underscores the effectiveness of combining geodetic and hydrological data for assessing groundwater circulation and optimizing groundwater management.

Because of the influence pore pressures have on effective stress, understanding hydrogeologic properties that control fluid flow and pressure distribution is important in characterizing earthquake and deformation processes. Here, we utilize borehole pressure changes in response to earth tides to determine hydrogeologic properties and their time variations for 17 boreholes within the NSF Earthscope’s Plate Boundary Observatory (PBO) network along the San Andreas fault and Cascadia subduction zone. Our analysis considers solutions for both confined and unconfined aquiares. Resulting permeability and hydraulic diffusivity values range from m² and , respectively, whereas specific storage values are generally . The values are fairly consistent through time, reasonable given lithology, and are comparable to other regional studies. For one borehole, values are also comparable to those determined with traditional aquifer test data. In contrast with previous determinations of the high-frequency poroelastic response to seismic waves, no obvious spatial trends in hydrogeologic properties determined from long-wavelength tidal perturbations are observed. Within the recurring time-series estimates, only one borehole exhibits clear permeability enhancement by earthquakes, whereas nearby boreholes with similar lithology and hydrogeologic property values do not. This highlights the variable susceptibility of rocks to permeability enhancement. Together, these results provide quantitative constraints useful for models of large-scale groundwater flow around large fault systems and the potential hydrologic influence on deformation and fault slip behavior.