Abstract Our understanding of the dynamics of mountain belt growth is hampered by the lack of high-resolution kinematic observations spanning entire orogenic belts. This is particularly the case for the structurally complex and nascent Tian Shan plateau. Here we use 8 years of Sentinel-1 data across 2 million square kilometres of the Tian Shan to show that the mountain range is extending along its strike, predominantly by rotating along a northeast-trending distributed shear zone. This zone is conjugate to the range strike but aligned with fast axes of shear-wave splitting measurements and a band of strike-slip earthquakes. We interpret this broad zone of shear as resulting from the clockwise rotation of the indenting Tarim Basin, which drives the northeast-to-east motion of the part of the Tian Shan southeast of the cryptic shear zone. Conjugate strike-slip components on numerous basin-bounding faults within the Tian Shan likely facilitate this escape. The present-day vertical deformation of Tian Shan results from a mix of tectonic, climatic, and anthropogenic forcings, with uplift of the highest peak facilitated by thrust along a south-dipping Nalati fault that could be promoted by deglaciation.

Our ability to measure the deformation at the Earth's surface over a range of spatial and temporal scales is vital for understanding seismic hazard, detecting volcanic unrest and assessing the impacts of vertical land movements (VLM) on sea level rise. Here, we combine 9-years of Sentinel-1 InSAR observations and continuous GNSS timeseries to build a high-resolution (1-km) national timeseries and velocity field of New Zealand from 2017 to January 2026. Utilising the higher spatial and temporal observations provided by Sentinel-1, we provide an updated estimate of the coastal VLM following the Kaikōura earthquake at 50–100 m resolution including updated estimates of the uncertainty and temporal variability.

Satellite geodesy provides critical insights into tectonic deformation, fault activity, and seismic hazard. However, in regions of widespread continental deformation, observational coverage has until recently relied on sparse GNSS measurements, limiting the resolution of short-wavelength deformation features. By integrating InSAR we can greatly improve the resolution, and we have recently constructed a transnational velocity field for the entire Alpine-Himalayan Belt at 1 km spacing, from over 222,000 Sentinel-1 SAR images (2016–2024) and a new compilation of GNSS velocities [Elliott et al., in review]. This dataset spans more than 11,000 km from southwestern Europe to eastern China, covering over 20 million km², and is referenced consistently to the Eurasian frame.From these velocities, we derive horizontal strain rates, providing near-continuous deformation mapping across the planet’s largest actively deforming region. Results reveal a bimodal pattern of tectonic strain, which is concentrated along major faults in some regions but distributed across broader zones in others. Vertical motions, in contrast, exhibit shorter-wavelength signals dominated by non-tectonic processes, particularly groundwater depletion.Satellite geodesy also provides critical insights into volcanic deformation and hazard, and we have processed InSAR data for the ~1300 subaerial volcanoes most likely to erupt. Scale is less of an issue for volcanoes, with volcanic activity usually confined to within 40 km of each volcanic centre, but timeliness is important for hazard monitoring, and we process data in near-real time form a subset of volcanoes. For historical analyses we have integrated our InSAR results with local GNSS networks [Bedon et al, in prep], but it remains a challenge to incorporate GNSS from multiple disparate networks for ongoing monitoring on a global basis.The spatial resolution of InSAR measurements is better than GNSS by orders of magnitude, but inclusion of GNSS is key for two reasons: firstly, for tying InSAR to a global reference frame and secondly, to provide a third component of the velocity field, which allows the full 3-D field to be constrained. However, the combination leads to very different resolutions in the north-south direction, constrained predominantly by GNSS, and the east-west direction, where InSAR dominates. When estimating the strain rate this leads to non-localisation of strain for north-south trending strike-slip faults and east-west trending dip-slip faults but also leads to short wavelength shear strain (e.g., from near-surface creep) being wrongly attributed to dilatation on faults of any orientation [Fang et al., 2024].We are addressing this issue in two ways. Firstly, by inclusion of along-track velocity estimates from Sentinel-1 burst overlap regions [Nergizci et al., 2024] and secondly by the addition of InSAR velocity measurements from NISAR. The left-looking nature of NISAR acquisitions will provide two more independent velocity measurement vectors that will enable full 3-D estimation at high resolution. Whilst the accuracy in the north-south direction will be ~4 times worse than in the east-west direction, the improvement in resolution will be by orders of magnitude.ReferencesElliott et al. (in review). Preprint: doi:10.31223/X5GX6B.Fang et al (2024). doi:10.1029/2024GL111199.Nergizci et al. (2024). doi:10.1016/j.procs.2024.06.401.

Globally, over 800 million people live within 100 km of a volcano. The contrast between geological and human timescales makes it notoriously difficult to predict when and where the next eruption will occur. However, the timescales of magma ascent mean that monitoring systems can detect changes, allowing scientists to judge changing likelihoods of hazardous events, to raise (and lower) volcanic alert levels if they are in place, and advise authorities, who may in turn decide to call evacuations. Thus volcano monitoring and advice saves lives and supports economic development. Despite this, many volcanoes near large population centres have little or no ground-based monitoring meaning most alerts do not accurate reflect hazard levels. Recent developments in satellite technology and machine learning are transforming the way we study our planet, changing our perception of volcanic activity and revolutionising the ways in which volcanoes are monitored. Here, we focus on the East African Rift system, where exposure is high and ground-based monitoring is scarce.First, we showcase how satellite data has enabled the systematic identification and characterisation of deformation at 16 otherwise unmonitored volcanoes, demonstrating a previously unrecognised, but extensive hazard. Then we discuss the scientific response to the 2024-2025 seismic crisis in the Fentale-Dofen Region, Ethiopia, which was caused by a sequence of magmatic intrusions over 6 months. UNOCHA report that 75,000 people were evacuated. The largest intrusion was ~ 50 km in length causing ~ 3 m of surface displacement and extensive surface fracturing. Satellite data and analysis provided by international organisations including the UK Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), the ERC Grant MAST (PI Biggs) and the GVEWERS programme of the CEOS Working Group on Disasters played a critical role in informing and supporting crisis response efforts. Real-time analysis was discussed with partners at Addis Ababa University and used by the Ethiopian Scientific Advisory Committee comprising scientists from Addis Ababa University, the Geological Institute of Ethiopia and other relevant institutions to monitor the events and keep the Ethiopian Disaster Risk Management Commission (EDRMC) and the public continuously informed. The advisory committee provided a highly simplified zoned map summarising the most likely scenarios and zones of hazard. Alongside this, a series of open-access Event Response Reports was published on the COMET website to support situational awareness and decision making by international stakeholders. For example, these reports supported the British Geological Survey (BGS) International Natural Hazards Forward Look (INHFL) reports and volcano advisory assessments for the UK’s Foreign, Commonwealth and Development Office (FCDO).This event highlights two pathways for scientists to address societal challenges, by engaging and supporting the process of decision-making. Firstly, that there is an urgent need for enhanced scientific monitoring, scientific expertise and preparedness in the East African Rift, particularly the infrastructural, and institutional capacities to support these efforts. Secondly satellite technology now provides monitoring data at sufficient spatial and temporal resolution to be used during crises, and if properly supported, could provide the foundation for global volcano monitoring systems.

As continental rifts evolve towards lithospheric break-up and the formation of an ocean ridge, basaltic dyke intrusion becomes the dominant mechanism of upper-crustal extension, surpassing tectonic faulting. The magmatic architecture within the rifting crust, which governs the availability and pathways of ascending magmas, therefore has a crucial role in the transition from continental- to oceanic-style rifting. Here we use olivine Fe–Mg interdiffusion chronometry to constrain the dynamics and timescales of magma ascent beneath the Main Ethiopian Rift, a continental rift of intermediate tectonic maturity. We find that magmas move rapidly through the crust, replenishing mid-crustal reservoirs only weeks to months before intrusive-eruptive events. Such ascent timescales are comparable to those of dyke intrusion recurrence observed during active phases at more mature rifts; hence, we infer that extensional activity in the Main Ethiopian Rift is probably mediated by the supply of magma from depth. The magmatic architecture and magma ascent rates we propose for the Main Ethiopian Rift indicate that well-established magma plumbing systems, capable of efficiently delivering melts to feed upper-crustal dykes, can develop in a continental rift even before substantial lithospheric thinning has occurred. Magmas beneath the Main Ethiopian Rift ascend through the crust on timescales of only weeks to months, indicating that, during continental rifting, a magmatic plumbing system can be well established before the lithosphere has thinned.

The rheology of Earth's lithosphere fundamentally governs tectonic processes and landscape evolution. Postseismic deformation following large earthquakes has been widely used to constrain rheological structures globally. However, regional-scale rheological variations remain poorly understood due to the infrequency of large earthquakes. The Bayan Har Block in the central-eastern Tibetan Plateau is a unique tectonic unit to investigate rheology regional-variations by pronounced high seismicity, heat flow anomalies, and localized lithospheric thinning. Here, we image postseismic deformation following the 2021 Maduo earthquake using InSAR and GNSS observations to probe the rheology over the block's north-east margin. We integrate long-term and short-term interferograms to separate deformation from atmospheric signals. After accounting for interseismic velocity, InSAR measurements extends out to 200 km from the rupture and its tips. Compared with prior studies, higher-quality far-field measurements allow the separation of viscoelastic relaxation from near-field afterslip effects. Our preferred model indicates a Burgers (bi-viscous) lower-crust rheology with transient and steady-state viscosities of 2.5 (+2.5/-1.3) x 10(1)(8) Pas and 2.5 (+0.7/-0.5) x 10(1)(9) Pas, respectively, beneath a 20-km-thick elastic layer. By testing laterally-variable and depth-dependent rheological structures, we identify a smaller intraplate-to-interplate viscosity contrast (factor of similar to 2) than that observed after the 2008 Wenchuan (factor of similar to 10) and 2001 Kokoxili (factor of similar to 5) earthquakes. This result suggests a positive correlation between viscosity contrasts, fault slip rates, and topographic gradients at a regional scale. These findings highlight that the rheological contrasts within the Bayan Har block exert a fundamental control on the long-term topographic evolution of the central Tibetan Plateau.

The India-Eurasia collision zone is the largest deforming region on the planet with numerous faults and widespread earthquakes, extending from the Himalayan Front to north of the Tien Shan. Developed from plate tectonic theory, block models have long been used to describe the crustal deformation in the collision zone, and GPS data are often invoked to constrain and test the models. Although previous block models perform well against GPS data on the whole, the detailed performance in many areas of the collision zone remains uncertain due to sparsity of GPS data and the low resolution of the fault database used to define the blocks. In this study, we process the raw GPS data collected via regional continuous GPS observation networks and Crustal Movement Observation Network of China (CMONOC) up to 2021, mainly located in Tibet, and obtain our core GPS velocity field with 420 continuous and 872 campaign stations. We further incorporate published GPS velocities, mainly located in the Himalaya and Tien Shan regions. We convert these velocities into our core solution to keep all the velocities in a consistent reference frame. As a result, we provide the densest and up-to-date GPS velocity field in the India-Eurasia collision zone including 2811 stations. Although the stations from CMONOC have been presented before, our updated velocities are more robust as they are derived from a longer time span, e.g., 5 years more than Wang and Shen [2020]. Also, we add an extra 351 stations for the collision zone compared to Wang and Shen [2020], most of which are continuous stations, over 300 of which have never been published. Wright et al. [2023] presented the first high-resolution InSAR velocity field for whole Tibet. Constraints from the InSAR data enable us to effectively evaluate the detailed performance of block modeling in Tibet, especially in the remote regions where the GPS data are sparse. We incorporate the GPS and InSAR velocity fields, and 170 Quaternary fault slip rates into a recently-developed high-resolution block model with 237 blocks by Styron [2022] to predict block motion and fault slip rates throughout the collision zone. The block model fits the data well in general, although there are some significant residuals. The predicted slip rates along ~900 faults from the model are generally small except for those along several major faults, including the major Tibetan strike-slip faults, which have larger slip rates but still within the level of 10 mm/yr, and the Main Himalayan Thrust, which has a convergence rate at the level of about 15 mm/yr. The predicted slip rates show along-strike variations, and are consistent with previous geodetic studies. We then use our results to assess the limitations of tectonic block modelling for applications in seismic hazard assessment and in understanding the geodynamics of continental tectonics. The results suggest that tectonic strain has two modes: a few major faults exhibit focused strain and high slip rates; between these major structures, deformation is more continuous.

On February 6, 2023, two devastating earthquakes, Mw7.8 and Mw7.5, struck the area surrounding Kahramanmaraş, Türkiye, resulting in extensive and complex surface deformations. The Mw7.8 event created a surface rupture over 310 km along the East Anatolian Fault, while the Mw7.5 earthquake resulted in a 150 km rupture along the Çardak-Sürgü Fault segment. Here we use Sentinel-1 Burst Overlap Interferometry (BOI) to improve 3D displacement mapping and in particular investigate near-fault deformation.In response to the earthquakes, previous studies have utilized various datasets, either separately or in combination. These include near and far-field seismic observations, continuous and campaign GNSS datasets, offset tracking from SAR satellites like Sentinel-1 and ALOS-2 and optical satellites such as Sentinel-2, and InSAR. These diverse data sources are vital for calculating the 3D displacement field. However, extracting information from standard interferograms, critical due to their high spatial resolution, is often challenging because of large phase gradients, particularly in the near field of fault ruptures.This issue frequently complicates the accurate determination of fault displacement and 3D decomposition in impacted areas. For Sentinel-1, with a range resolution of approximately 5 m, displacement in the range direction is usually determined with acceptable accuracy using range offset tracking. However, the azimuth resolution of about 20 m makes azimuth offset tracking less precise. This lower resolution frequently results in less reliable displacement constraints in the azimuth direction. To overcome this limitation, we produced Burst Overlap Interferograms (BOI) from four different tracks of Sentinel-1. These BOI results enabled more precise measurements of along-track displacement near the fault lines, which are theoretically proportional to the number of looks and the decorrelation noise.A key aspect of our methodology was the unwrapping process of the BOI, guided by azimuth offset tracking to handle large displacements exceeding ~1.5 m in the azimuth direction. For the 3D displacement field, we referenced all offset and BOI data to zero points away from the co-seismic ruptures and removed planar ramps. Uncertainties were empirically estimated as the mean absolute deviation in 4x4 pixel windows for offset data and 2x2 pixel windows for BOI. These uncertainties were then used to weight 3D motion inversion and decomposed displacements, providing a more reliable depiction of the earthquake impact. Our approach, combining east and north motion fields, allowed us to extract precise surface slip distributions and highlight surface ruptures through detailed strain analysis. In this study, we explored how to extract more accurate deformation in the north-south direction and reveal detailed deformation near faults by applying 3D decomposition with jointly inverted all datasets in together. We will discuss the implications of our findings for our understanding of earthquakes, and in particular for understanding distributed off-fault deformation that occurs near the fault rupture.

The Sentinel-1 satellite's short revisit time is advantageous for maintaining better coherence in interferograms over short intervals, resulting in more accurate assessments of rapid deformation. However, the use of shorter-interval, multilooked interferograms may introduce a bias, known as a "fading signal," in the interferometric phase, leading to unreliable velocity estimates.In the first part of our research, funded by the European Space Agency (ESA), we explore characterizing phase bias, focusing on one of its primary indicators—the closure phase. We explore loop closure time-series across various datasets, considering different look directions (ascending and descending), evaluating the impact of filtering and multilooking on closure phases, investigating loop closures across diverse landcovers, and examining the polarization dependency of closure phases. Additionally, we establish correlations between the time series of phase closures and various environmental proxies.In the second stage, we present our progress on developing a universally applicable phase bias correction. We previously developed an empirical mitigation strategy that corrects the phase bias based on the assumption that the change in strength of the bias in interferograms of different length has a constant ratio (Maghsoudi et al. 2022). In this presentation, we investigate the applicability of the proposed method across various scenarios and compare it with alternative approaches.Correcting for the phase bias is particularly important for InSAR processing systems, such as the COMET LiCSAR system (Lazecký et al. 2020), which aims to study geohazards over large areas. ReferencesMaghsoudi, Y., Hooper, A.J., Wright, T.J., Lazecky, M., & Ansari, H. (2022). Characterizing and correcting phase biases in short-term, multilooked interferograms. Remote Sensing of Environment, 275, 113022Lazecký, M., Spaans, K., González, P.J., Maghsoudi, Y., Morishita, Y., Albino, F., Elliott, J., Greenall, N., Hatton, E., Hooper, A., Juncu, D., McDougall, A., Walters, R.J., Watson, C.S., Weiss, J.R., & Wright, T.J. (2020). LiCSAR: An Automatic InSAR Tool for Measuring and Monitoring Tectonic and Volcanic Activity. Remote Sensing, 12

Postseismic deformation occurs due to stress relaxation following large earthquakes and has been widely captured by space geodetic observations. For some earthquakes, afterslip has been inferred to take place in the fault barriers surrounding the areas of coseismic asperities. This phenomenon can be explained by the velocity-strengthening frictional behavior prevalent in the barriers and velocity-weakening frictional properties in the asperities. However, for some events, afterslip seems to exhibit spatial overlap with the coseimsic slip. Here we used postseismic deformation of the Maduo earthquake to investigate the afterslip pattern and fault friction properties. The 2021 Mw 7.4 Maduo earthquake ruptured ~150 km of the Jiangcuo fault, a previously-poorly known NWW-trending, sinistral strike-slip fault which lies within the Bayan Har block of the eastern Tibetan Plateau. Here we use ~2 years (between May 2021 and August 2023) of Sentinel-1 interferometric synthetic aperture radar (InSAR) data to study the postseismic deformation following the Maduo earthquake. Additionally, we use ~7 years (between October 2014 and May 2021) of InSAR data to obtain the interseismic velocity. We remove the interseismic components from postseismic data through transforming both datasets into Eurasian reference frame based on GPS velocities. Both descending and ascending postseismic data reveal notable localized postseismic deformation in the middle segment of the seismogenic fault, and diffused deformation in the far field. We apply a kinematic inversion to model the afterslip based on the cumulative postseismic displacement. We find that significant afterslip occurred on shallow (0–5 km) fault segments that also slipped coseismically . We then conduct dynamic earthquake cycle simulations incorporating vertical variations of frictional properties to understand the conditions where this can occur. We show that velocity-strengthening properties in the shallow region can rupture seismically and creep during postseismic period. Our dynamic model partially explains the overlapping slip of co- and postseismic slip of the Maduo earthquake. However, this model requires shallow interseismic creep, which is either not observed, or is obscured by noise in our data. Reference Lazecký, M., Spaans, K., González, P.J., et al. (2020). LiCSAR: An Automatic InSAR Tool for Measuring and Monitoring Tectonic and Volcanic Activity. Remote Sens., 12, 2430. Morishita, Y., Lazecky, M., Wright, T.J., et al. (2020). LiCSBAS: An Open-Source InSAR Time Series Analysis Package Integrated with the LiCSAR Automated Sentinel-1 InSAR Processor. Remote Sens., 12, 424. Ou, Q., Daout, S., Weiss, J. R., et al. (2022). Large-scale interseismic strain mapping of the NE Tibetan Plateau from Sentinel-1 interferometry. J. Geophys. Res. Solid Earth, 127, e2022JB024176. Amey, R. M. J., Hooper, A., Walters, R. J. (2018). A Bayesian method for incorporating self‐similarity into earthquake slip inversions. J. Geophys. Res. Solid Earth, 123, 6052–6071. Allison, K. L., Dunham, E. M. (2018). Earthquake cycle simulations with rate-and-state friction and power-law viscoelasticity. Tectonophysics, 733, 232– 256.

Earthquakes release strain energy that has accumulated between seismic events. Measuring strain accumulation rates is critical for understanding earthquake cycle and assessing earthquake potential, with fault slip rates serving as essential inputs for seismic hazard models. However, the Tibetan Plateau has been lacking comprehensive estimates of geologic slip rates on numerous faults. To address this gap, geodetic data have been invoked to derive fault slip (or slip deficit) rates using various methodologies. These include the commonly adopted classic and deformable block modelling approaches (Meade & Loveless, 2009) and the newly developed direct inversion of geodetic strain rates (Johnson et al., 2022), which has the advantage of not requiring blocks to be defined. A comprehensive comparison of slip rates obtained from these different geodetic methods has been notably absent.In this study, we focus on the southeastern Tibetan Plateau, utilising Sentinel-1 satellite data from 35 ascending and 32 descending frames spanning the period between 2014 and 2023, along with published GNSS velocities. We constructed high-resolution (1 km) maps of velocity and strain rate fields covering 1.3 million km2. Using these maps, we derived slip rates on newly mapped faults (Styron, 2022) using classic block modelling, “deformable block” modelling, and by the direct inversion of strain rates. Our strain rate fields reveal a partition through focused shear on the Kunlun fault, the Xianshuihe-Xiaojiang fault system, the Longriba fault, the Longmenshan fault possibly influenced by the ongoing postseismic deformation of the 2008 Mw 7.9 Wenchuan earthquake, and the Lijiang-Xiaojinhe fault. On the deforming plateau there is diffuse deformation away from the major faults, with average shear strain and dilatation rates of 14.3 and 13.1 nanostrain/year, compared to 9.4 and 11.1 nanostrain/year in the Sichuan basin (which likely reflects the noise floor in the data). The geodetically-determined slip rates from the three methods generally align with available geologic rates, particularly along-strike variations on the Kunlun fault and the Xianshuihe-Xiaojiang fault system. Our block model consists of 103 blocks bounded by 326 fault sections in the southeastern Tibetan Plateau. The model is constrained by the combined geodetic horizontal velocities from 6617 observation points. Classic block modelling without considering internal strain tends to overestimate slip rates on faults that slip faster than 5 mm/yr, compared to deformable block model that accounts for homogeneous intrablock strain, constituting 5% of the total. The two block models explain approximately 45-50% of the geodetic strain, predicting focused strain on block boundaries even in the absence of observed strain concentrations. By directly inverting strain rates, we suggest that 40-50% of the geodetic strain is attributable to elastic coupling (back slip) on faults, while the remaining can be explained by off-fault distributed moment sources (body forces) in a thin elastic plate. We discuss limitations of different geodetic approaches in modelling deformation (velocities or strain rates) and implications for seismic hazard by comparing the seismic moment release rate from earthquakes and the geodetic moment accumulation rate from our geodetic models.

In continental rifts, tectonic deformation, magmatic processes, and earthquakes interact dynamically reflecting the crust’s complex response to extensional stress and evolving subsurface and surface conditions. Recent seismotectonic activity in the Fentale-Dofen region of the Main Ethiopian Rift was driven by the intrusion of several dykes reaching up to 50 km in length observed using satellite radar interferometry. Over 300 earthquakes with magnitude 4 or greater were reported by international seismic networks and the GNSS site at Addis Ababa moved 20 mm to the west. These and other observations on the ground were used to create a highly simplified hazard map and 75,000 people were evacuated. Although no magmatic eruption occurred, the earthquakes triggered landslides and caused infrastructure damage, especially to buildings and roads. Here we provide a preliminary analysis of the patterns of earthquakes, ground deformation, and surface manifestations from 2024 to 2025, with a focus on the underlying mechanisms contributing to seismic sequences in the area and key unresolved scientific questions. We discuss how scientific evidence was used to inform decision-makers and examine the short- and long-term implications for critical infrastructure and nearby communities. Finally, we emphasize the importance of real-time monitoring, proactive risk management, and the need for continuous observation and improved early warning systems to reduce future seismic and volcanic risks.

Between September 2024 and March 2025, a sequence of magmatic dyke intrusions occurred between Fentale and Dofen volcanoes, Ethiopia. Due to infrastructure damage, surface fissures and potential eruptions, ~75,000 people were evacuated in January 2025. Ground access to the region remains limited. This data report summarises satellite analysis conducted by the UK Centre for the Observation and Modelling of Volcanoes, Earthquakes and Tectonics (COMET) at the request of colleagues from Addis Ababa University and published online as a series of eight event response reports. We used data from Sentinel-1, Sentinel-2, COSMO-SkyMed, Pléiades and PlanetScope satellites to document the activity in real-time. Steady uplift around Fentale between 2017-2024 was followed by the intrusion of a 7 km long dyke in September-October 2024. A second, larger dyke intrusion occurred between December 2024 and March 2025. The dyke initially propagated radially, before changing direction to propagate along the rift axis, reaching 50 km in length and causing ~3 m of surface displacement. Dyke propagation stopped by mid-January, but opening continued at a variable but generally decreasing rate until mid-March. Activity within Fentale caldera, including ~ 30 cm of localised subsidence, thermal anomalies, visible plumes, and methane emissions started in mid-January. Following a magnitude 5.9 non-double-couple earthquake on 14 February, the area of localised subsidence slumped by up to 30 m. This information was used to support situational awareness and decision making by stakeholders in Ethiopia and UK. Ongoing monitoring remains critical.

We present a survey of deformation in the Ecuadorian Inter-Andean valley and surrounding regions from satellite radar and GNSS between 2017 and 2023, including anthropogenic, tectonic, landsliding and volcanic processes. Major anthropogenic signals include urban subsidence associated with water and resource extraction in Quito (-3.5 mm/yr), Canar (+1.8 mm/yr) and Guayaquil (+similar to 8 mm/yr). We also observe significant horizontal deformation caused by the interaction between the subduction zone and active tectonic faults. Four of Ecuador's 21 continental volcanoes are actively deforming and we also observed the continued subsidence of old volcano-sedimentary deposits in the northeast of the city of Cuenca. We examine the portion of the Chingual-Cosanga-Pallatanga-Puna right-lateral fault (CCPP) between the cities of Pallatanga and Riobamba and determine the geodetic slip rate and strain rate of this particular segment of the fault system and subsequently compare it with previously estimated geological slip rates. We estimated a slip rate of 3.1 +/- 0.6 mm/yr, with shear strain ranging from 50 to 100 nst/yr, extending beyond the primary fault trace. Furthermore, shear strain extends southeastward (within a range of 16-30 km), where significant active branches of this complex fault system exist, with a slip rate of 2.7 +/- 0.3 mm/yr. This study highlights specific areas for future monitoring of geohazards and infrastructure resilience in Ecuador, with particular relevance for similar Andean settings.

AbstractFault slip rates estimated from geodetic data are being integrated into seismic hazard models. The standard approach requires modeling velocities and relative (micro‐)plate motions, which is challenging for fault‐based models. We present a new approach to directly invert strain rates to solve for slip rates and distributed strain simultaneously. We generate velocity and strain rate fields over the southeastern Tibetan Plateau, utilizing Sentinel‐1 Interferometric Synthetic Aperture Radar data spanning 2014–2023. We derive slip rates using block modeling and by inverting strain rates. Our results show a partitioning between localized strain on faults and distributed deformation. The direct inversion of strain rates matches the geodetic data best when incorporating distributed moment sources, accounting for a similar proportion to on‐fault sources. The direct strain methodology also aligns best with the independent geological slip rates, especially near fault tips. As high‐resolution strain rate fields become increasingly available, we recommend direct inversion as the preferred practice.

Accurate monitoring of ground deformation is important for understanding the processes that lead to natural disasters, and the health and safety of society. The discovery of a fading signal has put the accuracy of methods that utilise multilooking and short-temporal interferograms into question. A symptom of this signal is that multilooked interferograms may exhibit a non-zero phase loop closure. We compare the phase loop closure in C-band and L-band InSAR data over different land cover types for an area centered on Milan, Italy. Our findings suggest that changes in volume scattering are the leading cause of phase loop misclosure and the fading signal in this area. We also investigate the effects of multilooking on the magnitude of phase loop misclosure with the goal of developing a model of the fading signal for both C-band and L-band InSAR.

We report sustained uplift throughout Volcan Sangay's most recent period of eruption (2019-22), moderated only by transient excursions during some of its largest explosions. Volcan Sangay (Amazonia, Ecuador), has been erupting since 2019, impacting both local communities and distant cities with ash fall and lahars. We analyzed ascending and descending Sentinel-1 radar imagery, constructing a robust network of interferograms spanning this eruptive period to measure relative ground displacements across the volcano. Our time series reveals a consistent uplift pattern ( 68 mm/yr) on the western and northern flanks of the volcano, which we attribute to volume increases in a body of magma located within the volcano's edifice beneath its western flank. This source appears to be vertically extensive, and is best fit by a quadrangular magma pathway, dipping towards the west and increasing in volume by 1.1 x 106 m3 between 2019 and 2022. We additionally identify non-magmatic deformation, including subsidence of fresh deposits and downslope displacement ( 50 mm/year) in the southeastern sector of the volcano. Co-eruptive uplift at Sangay is a rare observation of endogenous growth during an eruption and indicates that stratovolcano edifice stability is sensitive to both magma flux into the edifice and shallow controls on eruption rate.

Major strike-slip faults that develop between strong and weaker regions are thought to focus along narrow shear zones at the rheological boundary. Here we present the InSAR-derived velocity field spanning almost the entire length of one such fault, the 1600 km-long Altyn Tagh Fault (ATF), and analyse the strain distribution. We find that localisation of strain is actually variable, in contrast to other major strike-slip faults that show little variation, with strain concentrated at the fault for some sections and distributed over broad (>100 km) shear zones for others. Slip rate along the ATF is also variable, decreasing along the fault from 11.6 ± 1.6 mm/yr in the west to 7.2 ± 1.4 mm/yr in the central portion, before increasing again to 11.7 ± 0.9 mm/yr over the eastern portion. We show that the variable shear zone width may be linked to geological variability and the influence of heat flow, and the results imply that sub-parallel faults play an important role in the overall deformation field. This demonstrates the significance of accurately characterising strain rates over a broad region when assessing seismic hazard.

Au cours des dernières décennies, le développement de l’InSAR et de la corrélation optique ainsi que l’augmentation considérable des données satellitaires ont révolutionné la mesure des déplacements de surface induits par l’activité sismique. Dans ce chapitre, nous présentons tout d’abord une vue d’ensemble de ce que nous avons appris en 30 ans d’InSAR tectonique. Pour chaque phase du cycle sismique, nous passons en revue l’histoire des études InSAR et ce qu’elles nous ont appris sur les failles et les tremblements de terre. Dans la deuxième partie du chapitre, nous nous concentrons sur l’étude des séismes de rupture en surface à l’aide de la corrélation optique. Nous décrivons brièvement la technique ainsi que ses avantages et ses limites. Nous montrons ensuite des exemples de champs de déplacement de surface 2D et 3D obtenus par corrélation optique. Enfin, nous passons en revue les connaissances sur les tremblements de terre et la mécanique des failles apportées par les champs de déplacement à haute résolution obtenus par corrélation optique.

The distribution and magnitude of forces driving lithospheric deformation in the India‐Eurasia collision zone have been debated over many decades. Here we test a two‐dimensional (2‐D) Thin Viscous Shell approach that has been adapted to explicitly account for displacement on major faults and investigate the impact of lateral variations in depth‐averaged lithospheric strength. We present a suite of dynamic models to explain the key features from new high‐resolution Sentinel‐1 Interferometric Synthetic Aperture Radar as well as Global Navigation Satellite System velocities. Comparisons between calculated and geodetically observed velocity and strain rate fields indicate: (a) internal buoyancy forces from Gravitational Potential Energy acting on a relatively weak region of highest topography (>2,000 m) contribute to dilatation of the high plateau and contraction on the margins; (b) a weak central Tibetan Plateau (∼1021 Pa s compared to far‐field depth‐averaged effective viscosity of at least 1022–1023 Pa s) is required to explain the observed long‐wavelength eastward velocity variation; (c) localized displacement on fault systems enables strain concentration and clockwise rotation around the Eastern Himalayan Syntaxis. We discuss the tectonic implications for rheology of the lithosphere, distribution of geodetic strain, and partitioning of active faulting and seismicity.