Spatially and temporally complex Central California aquifer storage is inferred from Sentinel-1a/b satellite radar imagery.

Interferometric synthetic aperture radar (InSAR) allows for mapping of crustal deformation on land with high spatial resolution and precision in areas with high signal-to-noise ratios. Efforts to obtain precise displacement time series globally, however, are severely limited by radar path delays within the troposphere. The tropospheric delay is integrated along the full path length between the ground and the satellite, resulting in correlations between the interferometric phase and elevation that can vary dramatically in both space and time. We evaluate the performance of spatially variable, empirical removal of phase-elevation dependence within SAR interferograms through the use of the K-means clustering algorithm. We apply this method to both synthetic test data, as well as to C-band Sentinel-1a/b time series acquired over a large area in south-central Mexico along the Pacific coast and inland--an area with a large elevation gradient that is of particular interest to researchers studying tectonic- and anthropogenic-related deformation. We show that the clustering algorithm is able to identify cases where tropospheric properties vary across topographic divides, reducing total root mean square (rms) by an average of 50%, as opposed to a spatially constant phase-elevation correction, which has insignificant error reduction. Our approach also reduces tropospheric noise while preserving test signals in synthetic examples. Finally, we show the average standard deviation of the residuals from the best-fit linear rate decreases from approximately 3 to 1.5 cm, which corresponds to a change in the error on the best-fit linear rate from 0.94 to 0.63 cm/yr.

We used data from 333 continuous GPS stations, including 26 stations installed in 2006‐2007 as part of a collaborative EarthScope experiment, to investigate how deformation is distributed near the Rio Grande rift (RGR). Our previous analysis, using data from 2006‐2010, was consistent with a nearly uniform east‐west distributed extensional strain rate of ~1.2 nε/yr (nanostrain/yr) along 5 profiles spanning a ~1000 km region. We built upon this analysis with additional GPS networks and longer time series of data spanning varying time ranges between 1993‐2018. In all 5 east‐west profiles, extensional strain rates are higher within and west of the fault‐defined rift zone than to the east. There is an east‐to‐west increase in Central New Mexico from 0.7±0.1 to 1.8±0.8 nε/yr that is significant at the 95% confidence level. We found elevated extensional and shear strain rates of over 10 nε/yr along parts of the central RGR, particularly along the southeast edge of the Colorado Plateau (CP) along part of the Jemez lineament, as well as elevated dilatational strain rates and uplift above the Socorro magma body. Results from Euler pole analysis of GPS velocities for sites within the CP show non‐rigid behavior with considerable deformation near the plateau margins and internal east‐west extension. Our results suggest the RGR is actively deforming in an evolving tectonic environment.

We explore the use of elastic Green’s functions in inversions of one‐dimensional Interferometric Synthetic Aperture Radar (InSAR) observations to recover three‐dimensional displacement fields. This approach enforces coupling of the horizontal displacements and limits the need for prior assumptions about the subsurface sources, driving the deformation or explicit damping of a given dimension of the full 3D deformation field. We apply these methods to data from the Coachella Valley, California, where artificial groundwater recharge in 2017 and the associated increases in pore pressure resulted in ground displacements of up to 12 cm. This area is covered by Sentinel‐1a/b data for two overlapping paths from both ascending and descending orbits, as well as an east‐west flight line from the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), providing five unique line‐of‐sight geometries. The regularization approaches applied to the Sentinel data alone agree in most respects, with the elastically coupled approach producing a slightly better fit to the independent UAVSAR observations. Our results suggest that the 2017 groundwater entrainment in the Coachella Valley is likely associated with significant horizontal displacements that led to contraction across the fault bounding the northern side of the basin, as well as increases in right‐lateral sense of strain in some areas along the fault.

Coastal subsidence exacerbates relative sea level rise, making low-lying areas vulnerable to flooding. In Hawai’i, the contribution of vertical land motion has not been fully studied. This is critical for urban O’ahu, where infrastructure is on low-lying coastal areas with varying sedimentary consolidation. Here we processed Interferometric Synthetic Aperture Radar data from 2006–2024 for the Hawaiian Islands, referencing them with Global Navigation Satellite System measurements to calculate subsidence rates. We also created a two-meter resolution digital elevation model for coastal O’ahu using 2007–2013 Federal Light Detection and Ranging data, which included hydro-enforcement and gap filling with reprocessed data. Using this elevation data and vertical land motion measurements, we numerically modeled flood exposure. Results suggest that while island-wide subsidence on O’ahu is about 0.6 ± 0.6 mm/yr, the south shore has localized rates exceeding 25.0 ± 1.0 mm/yr. This subsidence, which is much faster than Hawaii’s long-term sea level rise rate (1.54 mm/yr since 1905), could expand flood exposure by up to 53% by 2050 in the Mapunapuna industrial region. Accounting for subsidence compresses the timeline for flood preparedness by up to 50 years, emphasizing the need to integrate these insights into planning and policy for sustainable development and flood mitigation.