Measurements of present‐day surface deformation are essential for the assessment of long‐term seismic hazard. The European Space Agency's Sentinel‐1 satellites enable global, high‐resolution observation of crustal motion from Interferometric Synthetic Aperture Radar (InSAR). We have developed automated InSAR processing systems that exploit the first ~5 years of Sentinel‐1 data to measure surface motions for the ~800,000‐km2 Anatolian region. Our new 3‐D velocity and strain rate fields illuminate deformation patterns dominated by westward motion of Anatolia relative to Eurasia, localized strain accumulation along the North and East Anatolian Faults, and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western Anatolia. We show that automatically processed Sentinel‐1 InSAR data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions. These results are important for assessing the relationship between strain accumulation and release in earthquakes.

Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of faults accumulating strain over centuries. Here, we show that strain accumulation rates calculated from geodetic measurements around a major transform fault are constant for its entire 250-year interseismic period, except in the ~10 years following an earthquake. The shear strain rate history requires a weak fault zone embedded within a strong lower crust with viscosity greater than ~1020 Pa s. The results support the notion that short-term geodetic observations can directly contribute to long-term seismic hazard assessment and suggest that lower-crustal viscosities derived from postseismic studies are not representative of the lower crust at all spatial and temporal scales.

The North Anatolian Fault (NAF) is a major tectonic feature in the Middle East and is the most active fault in Turkey. The central portion of the NAF is a region of Global Navigation Satellite Systems (GNSS) scarcity. Previous studies of interseismic deformation have focused on the aseismic creep near the town of Ismetpasa using radar data acquired in a single line‐of‐sight direction, requiring several modeling assumptions. We have measured interseismic deformation across the NAF using both ascending and descending data from the Envisat satellite mission acquired between 2003 and 2010. Rather than rejecting incorrectly unwrapped areas in the interferograms, we develop a new iterative unwrapping procedure for small baseline interferometric synthetic aperture radar (InSAR) processing that expands the spatial coverage. Our method corrects unwrapping errors iteratively and increases the robustness of the unwrapping procedure. We remove long wavelength trends from the InSAR data using GNSS observations and deconvolve the InSAR velocities into fault‐parallel motion. Profiles of fault‐parallel velocity reveal a systematic eastward decrease in fault slip rate from 30 mm/yr (25–34, 95% confidence interval (CI)) to 21 mm/yr (14–27, 95% CI) over a distance of ∼200 km. Direct offset measurements across the fault reveal fault creep along a ∼130 km section of the central NAF, with an average creep rate of 8 ± 2 mm/yr and a maximum creep rate of 14 ± 2 mm/yr located ∼30 km east of Ismetpasa. As fault creep is releasing only 30–40% of the long‐term strain in the shallow crust, the fault is still capable of producing large, damaging earthquakes in this region.