Geodetic analysis of postseismic responses to major earthquakes offers insight into potential subsequent seismic activities and aseismic strain release. Interferometric Synthetic Aperture Radar (InSAR) provides a particularly high-resolution imaging capability for such transient events, particularly in regions without dense Global Navigation Satellite Systems (GNSS) networks. However, InSAR suffers from decorrelation errors and atmospheric noise, which can distort the interpretation of deformation patterns. To take a step towards addressing these challenges, this study introduces an advanced InSAR processing workflow and applies it to Sentinel-1 observations of postseismic deformation following the 2021 Haiti earthquake. We address decorrelation errors by employing phase linking through the Fine Resolution InSAR with Generalized Eigenvectors (FRInGE) method. We compare three methods for mitigating atmospheric effects, including a grouped Independent Component Analysis (ICA) method, and find that ICA performs best in removing atmosphere. Without applying these methods most of the signal is lost or hidden in the noise; after processing transient postseismic deformation, likely related to shallow fault creep, can be observed over ~3 months following the earthquake on the eastern EPGFZ. We compare the estimated cumulative slip to that obtained from ALOS-2 observations and find a good match, with ~3 cm of differential displacement on either side of the EPGFZ east of the rupture area. Our workflow provides a method for more precise characterization of localized transient deformation signals using C-band InSAR.

Continued global warming is expected to result in drying of Central America, with projections suggesting a decrease in precipitation. Poor hindcasting of precipitation, however, due in part to spatial and temporal limitations in instrumental data, subjects these projections to considerable uncertainty. Paleoclimate proxy data are therefore critical for understanding regional climate responses during times of global climate reorganization. Here we present two lake-sediment based records of precipitation variability in Guatemala along with a synthesis of Central American hydroclimate records spanning the last millennium (800-2000 CE). The synthesis reveals that regional climate responses have been strikingly heterogeneous, even over relatively short distances. Our analysis further suggests that shifts in the mean position of the Intertropical Convergence Zone, which have been invoked by numerous studies to explain variability in Central American and circum-Caribbean proxy records, cannot alone explain the observed pattern of hydroclimate variability. Instead, interactions between several ocean-atmosphere processes and their disparate influences across variable topography have resulted in complex precipitation responses. These complexities highlight the difficulty of reconstructing past precipitation changes across Central America and point to the need for additional paleo-record development and analysis before the relationships between external forcing and hydroclimate change can be robustly determined. Such efforts should help anchor model-based predictions of future responses to continued global warming.

An outstanding question for induced seismicity is whether the volume of injected fluid and/or the spatial extent of the resulting pore pressure and stress perturbations limit rupture size. We simulate ruptures with and without injection-induced pore pressure perturbations, using 2-D dynamic rupture simulations on rough faults. Ruptures are not necessarily limited by pressure perturbations when 1) background shear stress is above a critical value, or 2) pore pressure is high. Both conditions depend on fault roughness. Stress heterogeneity from fault roughness primarily determines where ruptures stop; pore pressure has a secondary effect. Ruptures may be limited by fluid volume or pressure extent when background stress and fault roughness are low, and the maximum pore pressure perturbation is less than 10% of the background effective normal stress. Future work should combine our methodology with simulation of the loading, injection, and nucleation phases to improve understanding of injection-induced ruptures.

The 2021 August 14 MW 7.2 Nippes, Haiti earthquake occurred 75 km west of the epicenter of the 2010 Leogane earthquake (Haiti) on the transpressive Caribbean - North America (CA-NA) plate boundary. We present an updated fault map for Hispaniola and model coseismic and early postseismic fault slip using Interferometric Synthetic Aperture RADAR (InSAR) and pixel offsets. We find the earthquake ruptured multiple segments of the Enriquillo-Plantain Garden Fault Zone (EPGFZ). Slip occurred in two main sub-events separated by 60 km on either side of a restraining bend at Pic Macaya, with ~2.7 m of peak reverse-slip east of the bend. To the west, slip jumps the restraining bend and further ruptures with ~1.3 meters of left-lateral slip. Afterslip in the four days following the event occurred at shallow depth and adjacent to the coseismic rupture areas and reached the surface to the east of Pic Macaya.