Journal Article

An InSAR‐GNSS Velocity Field for Iran

Elliott, John R., Lazecký, Milan, Walters, Richard J., Maghsoudi, Yasser, Watson, Andrew R., McGrath, Jack D.

2024

Overview

We present average ground‐surface velocities and strain rates for the 1.7 million km2 area of Iran, from the joint inversion of InSAR‐derived displacements and GNSS data. We generate interferograms from 7 years of Sentinel‐1 radar acquisitions, correct for tropospheric noise using the GACOS system, estimate average velocities using LiCSBAS time‐series analysis, tie this into a Eurasia‐fixed reference frame, and perform a decomposition to estimate East and Vertical velocities at 500 m spacing. Our InSAR‐GNSS velocity fields reveal predominantly diffuse crustal deformation, with localized interseismic strain accumulation along the North Tabriz, Main Kopet Dagh, Main Recent, Sharoud, and Doruneh faults. We observe signals associated with recent groundwater subsidence, co‐ and postseismic deformation, active salt diaprism, and sediment motion. We derive high‐resolution strain rate estimates on a country‐ and fault‐scale, and discuss the difficulties of mapping diffuse strain rates in areas with abundant non‐tectonic and anthropogenic signals. Plain Language Summary Across the entire country of Iran, the ongoing convergence of the Arabian and Eurasian tectonic plates at about two cm every year is deforming the Earth's crust, producing earthquakes in this process of continental collision. Accurate measurements of how the ground is moving today are critical to understanding both the county‐scale deformation, and the local‐scale earthquake hazard, where the crust is deforming quickly and building up strain that is likely to be released in future major earthquakes. We combine multiple series of satellite radar images with GPS velocities to estimate East and vertical ground motion across all of Iran, at a higher level of detail than previous GPS‐only studies have been able to capture. Our velocity fields show a complex mix of ground motion signals, from crustal deformation on a country‐scale, to rapid land subsidence caused by the extraction of groundwater from aquifers. Some of the major faults are clearly building up strain for future earthquakes, but other regions are deforming much more diffusely, making it difficult to ascertain the locations of any future seismic hazard and ground shaking. Key Points We generate high‐resolution East and vertical velocity fields for Iran using Sentinel‐1 InSAR and GNSS observations Regional deformation is diffuse, with interseismic strain localized onto the Doruneh, Main Kopet Dagh, North Tabriz, and Sharoud faults Iran contains a wealth of time‐varying, short‐wavelength signals associated with groundwater extraction, salt diaprism, and sediment motion

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Anthropogenic factors / Aquifers / Average velocity / Crustal deformation / Deformation / Earth crust / Earthquakes / Fault lines / Geological hazards / Global navigation satellite system / Global positioning systems / GPS / Ground motion / Groundwater / InSAR / Interferometric synthetic aperture radar / interseismic / Iran / Land subsidence / Movement / Plate tectonics / Plates (tectonics) / Radar / Radar imaging / Satellite imagery / Satellite navigation systems / Satellite radar / Seismic activity / Seismic hazard / Shaking / Strain rate / Subsidence / Surface velocity / Synthetic aperture radar interferometry / Velocity / Velocity distribution / velocity field / Vertical motion / Vertical velocities