Conference Agenda

Large earthquakes are commonly followed by postseismic stress relaxation in the surrounding lithosphere, including viscoelastic flow in the lower crust and upper mantle. These processes provide a valuable opportunity to constrain lithospheric rheological properties such as viscosity. On 6 February 2023, two major strike-slip earthquakes (Mw 7.8 and Mw 7.6) ruptured the East Anatolian Fault (EAF), the plate boundary between the Arabian and Anatolian plates. The coseismic rupture extended over ~500 km with peak slip exceeding 10 m, suggesting substantial postseismic deformation.

To characterize the postseismic deformation, we processed Sentinel-1 SAR data spanning two years after the earthquakes. Time-series InSAR was used to retrieve line-of-sight (LOS) displacements, while burst overlap interferometry (BOI) was applied to derive azimuthal displacements. We analyzed three ascending and three descending tracks, each consisting of 4–5 standard frames, enabling reconstruction of the full four-dimensional surface deformation field (temporal evolution and east-west, north-south, and vertical components).

Our results reveal pronounced spatial and temporal asymmetry in horizontal postseismic deformation across the EAF. Deformation on the Arabian plate decays more slowly than on the Anatolian side, indicating a mechanically stiffer lithosphere to the southeast. While spatial asymmetry alone could result from either lateral viscosity variations or elastic afterslip within a heterogeneous crust, the observed asymmetric temporal decay is consistent only with contrasting viscosities across the fault. Elastic afterslip would produce nearly synchronous surface motion on both sides of the fault and thus a symmetric temporal decay pattern. By independently modeling surface displacements on each side of the EAF, we infer a strong interplate viscosity contrast, with upper-mantle viscoelastic flow dominating the postseismic deformation relative to afterslip.

In addition to horizontal deformation, significant vertical postseismic signals are observed. These are well explained by poroelastic rebound, requiring a Poisson’s ratio change of approximately 0.10–0.13 between undrained (coseismic) and drained (postseismic) conditions, indicating substantial earthquake-induced modification of crustal material properties.

This study presents the first unambiguous observation of asymmetric temporal decay in postseismic deformation resolved by satellite InSAR. For large strike-slip earthquakes along plate boundaries, our comprehensive three-dimensional time-series deformation analysis provides critical constraints on dominant postseismic processes and the underlying rheological structure of the lithosphere.

Understanding how continental deformation is distributed in space and evolves through time is a central question in active tectonics, with important implications for lithospheric rheology and seismic hazard. While the upper crust accommodates strain through brittle failure during earthquakes, the lower crust and mantle relax stress through viscous flow. The rates and mechanisms of this relaxation vary both spatially and temporally, complicating interpretation of present-day strain rates and their relevance to long-term earthquake risk.

Decadal geodetic observations provide a valuable window into the temporal evolution of crustal deformation. Yet regional strain rate fields, including those measured by Sentinel-1 InSAR across the Tibetan Plateau (Wright et al., 2026) and the broader Alpine-Himalayan Belt (Elliott et al., 2026), may be contaminated by long-lasting postseismic transients. Moreover, previously inferred lithospheric strengths span several orders of magnitude, arising from differences in constitutive assumptions, as well as the spatial coverage and time span of the available observations.

Here we present a comprehensive geodetic study of long-lived deformation following the 2001 Mw 7.8 Kokoxili earthquake on the Kunlun fault, Tibet. We integrate GNSS observations (2001-2025) with multi-mission InSAR time series from ENVISAT (2003-2010) and Sentinel-1 (2016-2024). Pre-earthquake measurements from ERS-1/2 (1992-2001) constrain an interseismic slip rate of <10 mm/yr on the Kunlun fault. We use the combined geodetic time series datasets to simultaneously invert for the temporal evolution of both fault afterslip and distributed viscous strain within a finite cuboidal volume in the mid-lower crust. Green’s functions are calculated to map the strain components of the deformable cuboids to surface displacements using an analytic solution for distributed anelastic deformation. We penalise isotropic strain to favour predominantly deviatoric deformation. We regularise the slip distribution and the strain tensor components using stress kernels. Strain directions within each cuboid are constrained by the coseismic stress changes induced by earthquake slip.

Results show that afterslip concentrates in regions of positive coseismic stress change, reaching amplitudes of ~1 m, with pronounced deep afterslip. Distributed deformation is dominated by deviatoric strain and exhibits strong contrasts across the fault (~10⁻⁵), with distinct temporal behaviours at different locations. By interpreting this in terms of the evolving driving stresses, we infer the time‑dependent viscosity of the mid-lower crust, without prescribing a priori flow laws. We discuss how this unified geodetic framework illuminates the spatiotemporal variability of lithospheric strength and advances our understanding of the time‑dependent behaviour of fault systems and continental shear zones.

References

T. J. Wright, G.A. Houseman, J. Fang, et al. (2026), High-resolution geodetic velocities reveal role of weak faults in deformation of Tibetan Plateau. Science, 391,499-503. https://www.science.org/doi/10.1126/science.adi3552

J.R. Elliott, J. Fang, M. Lazecký, et al. (2026), Deformation, strains and velocities for the Alpine Himalayan Belt from trans-continental Sentinel-1 InSAR & GNSS. Remote Sensing of Environment. https://doi.org/10.1016/j.rse.2026.115320

The East Anatolian Fault Zone (EAFZ) is a major left-lateral plate boundary accommodating motion between the Anatolian and Arabian plates. Its slip rate decreases south-westward from ~10 mm/yr along the central EAF to ~4 mm/yr near the Amanos segment, close to the Arabia-Africa-Anatolia triple junction. On 6 February 2023, two large earthquakes (Mw 7.8 and Mw 7.6) ruptured ~350 km of the EAFZ and an additional ~150 km along the Çardak-Doğanşehir fault system, providing a unique opportunity to investigate post-seismic deformation across a mechanically complex plate boundary.

Here we quantify the post-seismic deformation using standard line-of-sight (LOS) InSAR and Subswath and Burst Overlap Interferometry (SBOI) to derive a three-dimensional (3D) displacement field. LOS InSAR constrains primarily vertical and east-west motion, while SBOI is sensitive to along-track (approximately north-south) displacements, which are critical in this tectonic setting. We integrate cumulative LOS and SBOI time series with 100 continuous GNSS stations spanning two years following the earthquake sequence.

Sentinel-1 data from COMET-LiCS frames are processed using LiCSBAS time-series analysis. To isolate tectonic signals, we apply corrections for atmospheric delays (GACOS), ionospheric effects derived from JPL-HR total electron content products, solid Earth tides, plate motion, and interseismic loading. After correction, LOS and SBOI cumulative time series are jointly aligned to GNSS observations at common 12-day epochs using a VELMAP-based referencing strategy, ensuring a consistent reference frame and minimizing long-wavelength residuals.

The resulting 3D time series reveals postseismic deformation extending up to ~300 km from the rupture zone. Deformation is coherently resolved in the east, north, and vertical components and is dominated by left-lateral motion along both the East Anatolian Fault and the Çardak-Sürgü Fault system. Cumulative horizontal displacements reach 100-150 mm near the fault zone. Approximately 30% of the total postseismic deformation occurred within the first 120 days, followed by ~20% during the subsequent 120 days, indicating a decaying transient signal.

This integrated 3D geodetic dataset provides one of the most detailed observations of postseismic deformation following the 2023 Kahramanmaraş earthquakes. The spatial and temporal evolution of deformation highlights complex interactions between fault slip and lithospheric processes, offering new constraints on the mechanical response of the Anatolian plate. The observed decay patterns raise important questions regarding the relative contributions of afterslip, viscoelastic relaxation, and poroelastic rebound to the postseismic deformation field. To investigate these mechanisms, we employ a cuboid-based volumetric strain modelling framework (Barbot et al., 2017; Qiu et al., 2018) to represent distributed lower-crustal deformation within an elastic half-space. This approach enables us to quantify depth-dependent anelastic strain and evaluate its contribution to the postseismic signal alongside conventional fault-based afterslip models.

Barbot, S., Moore, J. D. P., & Lambert, V. (2017). Displacement and stress associated with distributed anelastic deformation in a half-space. Bulletin of the Seismological Society of America, 107(2), 821–855. https://doi.org/10.1785/0120160237

Qiu, Q., Moore, J. D. P., Barbot, S., Feng, L., & Hill, E. M. (2018). Transient rheology of the Sumatran mantle wedge revealed by a decade of great earthquakes. Nature Communications, 9(1), 995. https://doi.org/10.1038/s41467-018-03298-6

Large, shallow earthquakes occurring on continental faults are often the most destructive, causing thousands of casualties worldwide each year. Strikingly, these earthquakes are also among the most informative for researchers seeking to advance our understanding of earthquake processes. Here we present three new lessons learned from InSAR data and modeling of recent devastating earthquakes in Myanmar and Türkiye. The first lesson challenges conventional views of seismic gaps, which are commonly used in earthquake hazard assessments. Here we investigate what fault rupture conditions allowed the 2025 magnitude 7.7 Mandalay earthquake in Myanmar to grow far beyond its anticipated size. The earthquake ruptured, at super-shear velocity, a known ~250 km long seismic gap on the Sagaing fault in Myanmar and then went beyond it to produce a much longer rupture of about 460 km. We used SAR data to map the fault rupture and constrain the fault slip distribution and dynamic rupture modeling to show that the location where the rupture process initiated, rather than the super-shear rupture speed, was critical for producing the long rupture. The latter two lessons focus on the Kahramanmaras earthquakes that occurred in early 2023 on and near the East Anatolian Fault in southern Türkiye. Here we used high-quality 3D coseismic displacement derivations from InSAR to quantify the amount and extent of “missing” elastic deformation near the fault ruptures, which we interpret as permanent off-fault damage. We show that this damage is larger and more extensive than previously recognized around earthquake ruptures, with more damage near geometrical complexities than along straight fault sections. This indicates that the long-term slip focused on the fault at surface is lower than the tectonic plate motion, meaning that geologic fault-slip determinations around the world might systematically underestimate earthquake hazard. Finally, we show that the post-seismic deformation after the Kahramanmaras earthquakes is both spatially and temporally asymmetric, providing a unique opportunity in distinguishing between possible post-seismic mechanisms. We show that while the spatial asymmetry can be explained by both afterslip and viscoelastic relaxation, the temporal asymmetry eliminates afterslip and shows that viscoelastic relaxation in the upper mantle is the key postseismic deformation mechanism following the earthquakes. This result will help to calibrate earthquake cycle models in the region and in similar tectonic environments around the world for better earthquake hazard assessments.

As one of the most seismic regions in Europe, the Balkan Peninsula experiences frequent destructive earthquakes, as recalled by a series of recent Mw ≥6 events causing substantial societal impacts. These earthquakes highlight the complex geodynamic framework shaped by the interplay between the Hellenic subduction, the Alpine compression, and the North Anatolian Fault.

The Balkans remain significantly under-instrumented compared to other parts of Europe. Previous GNSS studies (e.g., Piña Valdés et al., 2022) provide a first-order analysis of the large-scale kinematics, revealing low strain rates (few mm/yr) across most of the region. However, the sparse and uneven station coverage fails to resolve deformation localized on individual active structures, limiting our understanding of the geodynamic processes at play and their associated hazards.

To overcome this spatial resolution gap, we take advantage of a new, extensive InSAR dataset over the western Balkans extending over 360, 000 km², processed by the FLATSIM service (Thollard et al., 2021) based on Sentinel-1 data. Leveraging the high spatial resolution (240 m) and frequent revisit times (6-12 days) of these 2014-2021 time series, we address two key methodological challenges: (i) accurately extracting the linear trend from InSAR LOS displacement time series, and (ii) referencing the derived mean velocity maps to a known reference frame. By adapting the approach from Lemrabet et al. (2023), we present the first consistent, large-scale InSAR average velocity field for the Balkan Peninsula, robustly referenced in ITRF14 (Altamimi et al., 2016) with minimal use of GNSS data. This referenced velocity field is in strong agreement with GNSS data (<1 mm/yr) while spatially complementing them.

This resulting kinematic map bridges the gap between local studies and regional tectonics, identifying localized tectonic deformation previously unresolved by sparse GNSS networks. We decompose the Line-of-Sight time series into vertical and horizontal velocity maps that constrain both the location and amplitude of velocity gradients across active structures. The InSAR horizontal velocity field is dominated by large-scale tectonic motion, while the vertical field is more heterogeneous, likely influenced by non-tectonic processes such as hydrology or anthropogenic activities.

Our kinematic analysis sheds light on several active features, including a 4-5 mm/yr east-west extension distributed over 80 km on both sides of a N–S axis in the inner Albanides. In Central Greece, we identify a major lithospheric shear zone extending over 250 km, accommodating more than 2 cm/yr of E–W dextral shear, potentially linked to the interaction between the North Anatolian Fault and the roll-back of the Hellenic subduction. Finally, our velocity field mosaic provides new constraints on the compression occurring in the Dinarides and Pannonian Basin.

This study confirms the capability of InSAR for resolving large-wavelength plate motion, even in challenging slowly straining areas, and provides a robust foundation for future tectonic surface deformation studies in this region and in other poorly instrumented areas. The resulting high-resolution velocity fields also provide improved input for strain calculation maps (Métois et al., 2025) and, more broadly, for seismic risk assessment. Beyond this first-order tectonic interpretation, the richness of the FLATSIM dataset also reveals numerous signals related to landslides, aquifer systems, and anthropogenic activity.

References :

Piña Valdés et al. (2022), 10.1029/2021JB023451

Thollard et al. (2021), 10.3390/rs13183734 / Dataset FLATSIM, 10.24400/253171/FLATSIM2020

Altamimi et al. (2016), 10.1002/2016JB013098

Lemrabet et al. (2023), 10.1029/2022JB026251

Métois et al. (2025), 10.55575/tektonika2025.3.1.99

Underground mining induces seismicity and surface displacement. In Poland, in the Legnica Glogow Copper District near Wroclaw, induced earthquakes are particularly frequent with earthquakes of Mw3 and larger occurring many times a year. These earthquakes have shallow hypocenters of often less than 1 km and mostly above the mined copper layer.

The area around the mines also experiences a fast continuous surface subsidence of several millimeters per year caused by rock as well as groundwater extraction. This surface motion is observed through geodetic measurements on the ground and from space. Across wide areas above the active mining the spatially very heterogeneous surface motion even exceeds 10 mm/yr. Also, sudden coseismic acceleration of surface motion is observed at the time of the larger earthquakes with moment magnitudes of Mw 3.5 and larger through space-borne InSAR based on ESA’s Sentinel-1 mission. In these cases, we often observe motion of several centimeters within a few days and with spatial extensions reaching a few kilometers. In some areas of high seismicity within the Copper district, the InSAR time series products of the European Ground Motion Service do not show ground motion measurements. Because there is man-made infrastructure, which usually provides persistent scatterers, this suggests that the ground motion there is far from linear in time.

Despite safety measures, the occurrence of some, also larger earthquakes is unexpected in space and time, which poses a particular threat to workers in the mines and also to the subsurface mine structures as well as generally to the people, settlements and infrastructure above ground.

Our study investigates a number of larger events of the recent years by analyzing the locally recorded seismic waveforms jointly with measurements of the surface displacements based on InSAR and partly GNSS measurements. We aim to precisely locate and describe the source processes of larger induced earthquakes by characterizing the interplay between shear-failure and collapse using full moment tensor models in a fully Bayesian and joint-data inference framework. Potentially we can relate collapse and shear failure induced by the mining activities in the context of other influences and improve our understanding of these unwanted events for mitigation measures.

The observations are best explained by often large negative isotropic components accompanied by significant shear failure mechanisms. Another finding is that our moment estimates systematically exceed the local catalog values. Challenges to be discussed are the impact of our short-duration point source model for possibly an accumulation of multiple events, possibly involving a larger volume and a longer duration, and the potential bias introduced by a simplified velocity model.