Assessment of present-day crustal deformation in the new Madrid Seismic Zone, Central United States, Using Integrated GNSS and InSAR Analysis

The New Madrid Seismic Zone (NMSZ) in the central United States is one of the most seismically active intraplate regions in North America, yet present-day surface deformation there is subtle and remains debated. This study integrates Global Navigation Satellite System (GNSS) and Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data to evaluate present-day deformation patterns across the NMSZ, the source region of the major 1811–1812 earthquake sequence. GNSS time-series analysis from station PTGV, located near Portageville, Missouri within the central NMSZ, was used to estimate station velocity in the IGS14 reference frame, providing a regional kinematic baseline. Sentinel-1 interferograms acquired between January and May 2021 were processed to generate unwrapped phase, coherence, and radar line-of-sight (LOS) displacement products for comparison with the GNSS-based regional kinematic reference. The results show LOS variability generally within approximately ±3 mm across the study area, without a spatially organized displacement signal aligned with the principal fault segments of the seismic zone, together with localized decorrelation and small subsidence patches in intensively cultivated areas of the Mississippi River valley. These observations are consistent with published geodetic studies indicating that present-day far-field strain accumulation across the NMSZ is low and near the detection limits of current techniques. The integrated GNSS–InSAR approach therefore provides a useful deformation baseline for the New Madrid region and supports future studies of intraplate strain accumulation, fault behavior, and geohazard evaluation in the central United States.